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--- |
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id: "24" |
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title: w10-设计模式 |
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slug: w10-design-patterns |
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status: draft |
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view_count: 0 |
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created_at: 2026-05-07T12:00:00+08:00 |
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updated_at: 2026-05-07T14:00:00.000000000+08:00 |
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--- |
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|
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# 高级程序设计 · 第10周 |
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### 设计模式：灵活性与可扩展性 |
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### 策略模式 + 工厂 + Repository 实战 |
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--- |
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### 📌 本周导航 |
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- W9回顾：骨架的成就与隐患 |
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- 策略模式：解析器的“插头标准” |
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- 解析器工厂：自动匹配的魔法 |
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- Repository：武装数据访问 |
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- 整体架构串联：调用链全程 |
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- 代码落地 + 实践任务 |
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- 架构反思 + W11 预告 |
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--- |
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|
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## 1️⃣ W9回顾：骨架的成就与隐患 |
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### 我们建了一座漂亮的房子 |
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|
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- ✅ MVC 分层清晰 |
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- ✅ Command 模式：**新增命令，Controller 零改动** |
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- ✅ 所有输出走 `ConsoleView` |
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- ✅ 工程包结构标准 |
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|
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--- |
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|
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### 但问题也随之而来 |
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```java |
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// CrawlCommand 里解析逻辑怎么办？ |
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if (url.contains("blog.example.com")) { |
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// 博客解析... |
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} else if (url.contains("news.example.com")) { |
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// 新闻解析... |
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} else { |
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view.printError("Unsupported website!"); |
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} |
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``` |
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> 😫 每支持一个新网站，就要加一个 `else if` |
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|
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--- |
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|
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### 还有另一个“裸奔”的数据 |
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```java |
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List<Article> articles = new ArrayList<>(); |
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// 所有 Command 都可以： |
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articles.clear(); |
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articles.add(null); |
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articles.remove(0); |
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``` |
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> 🚨 数据没有任何保护，靠口头约定是靠不住的 |
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|
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--- |
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|
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### 本周任务 |
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1. **解析逻辑可插拔** → 策略模式 + 工厂 |
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2. **数据访问加守卫** → Repository 模式 |
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|
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> W9 搭骨架，W10 装盔甲 |
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|
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--- |
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|
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## 2️⃣ 策略模式：解析器的“插头标准” |
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|
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### 墙上的插座，为什么什么电器都能插？ |
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- **三孔插座** 是标准接口 |
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- 电视、电脑、手机充电器都实现这个接口 |
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- 插座不关心你是什么电器 |
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|
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--- |
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|
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### 爬虫的世界也一样 |
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- `CrawlStrategy` = 插座接口 |
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- `BlogStrategy`、`NewsStrategy` = 具体电器 |
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- `CrawlCommand` = 使用电器的人 |
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- `StrategyFactory` = 插座面板 |
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--- |
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### 接口即合同 |
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```java |
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public interface CrawlStrategy { |
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List<Article> parse(String url, Document doc); |
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boolean supports(String url); |
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} |
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``` |
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|
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- `supports()`：我能不能处理这个 URL？ |
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- `parse()`：怎么解析？ |
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- **任何网站想被爬，签这份合同！** |
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--- |
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|
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### 策略 vs 硬编码 |
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| 维度 | if-else 屎山 | 策略模式 | |
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|------|-------------|----------| |
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| 新增网站 | 改 Command | 新建策略类 | |
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| 修改解析 | 翻找 else if | 只改对应类 | |
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| 测试 | 启动整个爬虫 | 单独测策略 | |
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| 开闭原则 | ❌ 修改开放 | ✅ 扩展开放，修改关闭 | |
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--- |
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|
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### 具体策略示例 |
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```java |
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public class BlogStrategy implements CrawlStrategy { |
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public boolean supports(String url) { |
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return url.contains("blog.example.com"); |
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} |
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public List<Article> parse(String url, Document doc) { |
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List<Article> articles = new ArrayList<>(); |
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for (Element e : doc.select(".post-title")) { |
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articles.add(new Article(e.text(), url, "")); |
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} |
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return articles; |
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} |
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} |
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``` |
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> ✨ 一个新网站，一个独立类，各扫门前雪 |
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|
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--- |
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|
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## 3️⃣ 解析器工厂：自动匹配的魔法 |
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### 谁来选择策略？ |
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- 如果 `CrawlCommand` 遍历所有策略 → 策略模式白用了 |
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- 我们需要一个黑盒子：**丢入 URL，返回合适的解析器** |
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--- |
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|
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### 工厂登场 |
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```java |
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public class StrategyFactory { |
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private final List<CrawlStrategy> strategies = new ArrayList<>(); |
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public StrategyFactory() { |
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strategies.add(new BlogStrategy()); |
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strategies.add(new NewsStrategy()); |
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} |
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public CrawlStrategy getStrategy(String url) { |
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for (CrawlStrategy s : strategies) { |
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if (s.supports(url)) return s; |
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} |
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return null; |
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} |
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} |
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``` |
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> 🔧 新增网站只需：新建策略类 + 工厂里注册一行 |
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--- |
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|
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### 开闭原则的胜利 |
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- ✅ `CrawlCommand` 完全不改 |
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- ✅ 新增 `XxxStrategy` 和一行注册 |
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- ✅ 所有策略的调用方式完全一致 |
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> 这就是 **“对扩展开放，对修改关闭”** |
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--- |
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### 重构后的 CrawlCommand |
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```java |
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public void execute(String[] args, ArticleRepository repository) { |
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String url = args[1]; |
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CrawlStrategy strategy = strategyFactory.getStrategy(url); |
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if (strategy == null) { |
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view.printError("No strategy for: " + url); |
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return; |
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} |
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Document doc = Jsoup.connect(url).get(); |
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List<Article> parsed = strategy.parse(url, doc); |
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for (Article a : parsed) { |
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repository.add(a); |
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} |
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view.printSuccess("Crawled " + parsed.size() + " articles."); |
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} |
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``` |
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|
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> 🧠 CrawlCommand 现在只做 **“调度”**，不做解析 |
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|
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--- |
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|
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## 4️⃣ Repository：武装数据访问 |
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### 共享 List 的问题 |
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```java |
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articles.clear(); // 清空 |
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articles.add(null); // 塞 null |
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articles.remove(0); // 随意删除 |
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``` |
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> 靠约定维护的秩序，终将被打破 |
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--- |
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|
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### 给数据装上防盗门 |
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```java |
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public class ArticleRepository { |
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private final List<Article> articles = new ArrayList<>(); |
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public void add(Article article) { |
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if (article == null) throw new IllegalArgumentException(...); |
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articles.add(article); |
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} |
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public List<Article> getAll() { |
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return Collections.unmodifiableList(articles); |
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} |
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public int size() { return articles.size(); } |
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public void clear() { articles.clear(); } |
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} |
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``` |
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|
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--- |
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|
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### 三道防线 |
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| 机制 | 作用 | |
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|------|------| |
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| **add 拒绝 null** | 规则写在代码里，不靠口头约定 | |
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| **getAll 返回不可变视图** | 任何修改立即抛异常 | |
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| **必须通过 repository 访问** | 封装内部结构，只暴露安全方法 | |
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--- |
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### 所有 Command 签名改变 |
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```java |
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// W9 |
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public void execute(String[] args, List<Article> articles); |
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// W10 |
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public void execute(String[] args, ArticleRepository repository); |
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``` |
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> 语义变化：从“给你数据随便玩” → “给你安全的存取通道” |
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--- |
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## 5️⃣ 整体架构串联 |
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### 一个 `crawl` 命令的完整旅程 |
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``` |
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用户输入 "crawl https://blog.example.com" |
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↓ |
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ConsoleView 解析 |
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↓ |
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Controller 路由 → CrawlCommand |
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↓ |
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StrategyFactory.getStrategy(url) → BlogStrategy |
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↓ |
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Jsoup 抓取 → Document |
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↓ |
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BlogStrategy.parse(url, doc) → List<Article> |
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↓ |
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Repository.add() 存储 |
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↓ |
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ConsoleView 输出成功信息 |
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``` |
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--- |
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|
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### 架构全景图 |
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 |
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```mermaid |
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flowchart TD |
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User(["👤 用户输入<br/>crawl https://blog.example.com"]) --> View |
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subgraph View["🎨 View 层 (ConsoleView)"] |
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ReadLine["readLine()"] |
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Display["display() / printSuccess()"] |
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end |
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ReadLine --> Controller |
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subgraph Controller["🧭 Controller 层"] |
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Router["CrawlerController<br/>Map 路由"] |
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end |
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Router --> Command |
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subgraph Command["⚡ Command 层"] |
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CrawlCmd["CrawlCommand<br/>(调度者)"] |
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end |
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CrawlCmd --> Factory |
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subgraph Strategy["🧩 Strategy 层"] |
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Factory["StrategyFactory<br/>(自动匹配)"] |
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StrategyI["<<interface>> CrawlStrategy"] |
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BlogS["BlogStrategy"] |
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NewsS["NewsStrategy"] |
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Factory --> StrategyI --> BlogS |
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StrategyI --> NewsS |
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end |
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BlogS --> Repository |
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subgraph Repository["🔐 Repository 层"] |
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Repo["ArticleRepository<br/>(add / getAll)"] |
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RepoList["List<Article> (私有)"] |
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Repo --> RepoList |
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end |
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RepoList --> Model |
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subgraph Model["📦 Model 层"] |
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Article["Article"] |
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end |
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CrawlCmd --> Display |
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Repository --> Display |
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``` |
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> 🗺️ 每一层都有清晰的职责，每一处扩展都只需要新增而不是修改 |
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|
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--- |
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|
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## 6️⃣ 代码落地（分步升级） |
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|
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### 从 W9 升级到 W10 的改动清单 |
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1. 新建 `strategy/` 包 → `CrawlStrategy` 接口 |
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2. 实现 `BlogStrategy`、`NewsStrategy` |
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3. 实现 `StrategyFactory` |
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4. 新建 `repository/` 包 → `ArticleRepository` |
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5. 修改 `Command` 接口签名 |
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6. 重写 `CrawlCommand` |
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7. 调整其他所有 `Command` |
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8. 调整 `Controller` 和 `App.java` |
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|
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--- |
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|
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### 关键代码演示 |
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|
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- `Collections.unmodifiableList()` 的用法 |
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- `StrategyFactory.getStrategy()` 的遍历逻辑 |
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- `CrawlCommand` 从“写死解析”到“调度组装” |
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|
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```java |
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// 一个改动示例 |
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for (Article a : parsed) { |
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repository.add(a); // 旧: articles.add(a); |
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} |
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``` |
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|
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--- |
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|
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### 找茬点 |
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|
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- `StrategyFactory` 没匹配到策略时返回 `null` |
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- `CrawlCommand` 检查 `null` 并报错 |
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- 有没有更优雅的方式避免 `null` 判断？ |
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|
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> 🔍 课后用 AI 探索 “空对象模式” 的前奏 |
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|
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|
--- |
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|
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## 7️⃣ 架构反思 + 下周预告 |
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|
|
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### 当前架构的脆弱点 |
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|
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- ❌ 异常处理单一笼统 |
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- ❌ 没有重试机制 |
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- ❌ 网络超时无控制 |
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- ❌ 日志仅输出到终端 |
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|
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|
--- |
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|
|
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### W11 目标：健壮性工程 |
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|
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- ✅ **自定义异常体系**：把“出错了”变成具体的业务异常 |
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- ✅ **工程化日志**：记录谁、什么时间、做了什么 |
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- ✅ **防御式编程 + 重试机制**：网络抖动不再致命 |
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|
||||
|
> W9 搭骨架 → W10 装盔甲 → W11 让它经得起毒打 |
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|
|
||||
|
--- |
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|
|
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## 8️⃣ 实践任务（现场） |
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|
|
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|
### 必做 |
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|
|
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|
1. 基于 W9 项目升级到 W10 |
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2. 至少实现 2 个 CrawlStrategy（可模拟） |
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3. 实现 `StrategyFactory` 和 `ArticleRepository` |
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4. 测试完整 `crawl` → `list` 流程 |
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|
|
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|
### 验收标准 |
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|
|
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|
- [ ] 新增策略只加类+注册，零改动旧代码 |
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|
- [ ] `getAll()` 返回不可修改视图 |
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|
- [ ] `CrawlCommand` 不含网站特定解析 |
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|
- [ ] 所有 Command 用 Repository |
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|
- [ ] 无地方直接操作 `List<Article>` |
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|
|
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|
--- |
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|
|
||||
|
## 9️⃣ 课后作业 |
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|
|
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|
### 必做 |
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|
|
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|
1. 完善 `ArticleRepository`：增加 `addAll`，防御 null |
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2. **★ AnalyzeCommand**：复用策略解析但不存储，输出统计信息 |
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|
3. **AI 架构审计**：发送类签名给 AI，检查策略解耦与封装 |
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|
|
||||
|
### 选做 |
||||
|
|
||||
|
- 正则策略匹配、默认策略、策略优先级 |
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|
- 思考题：两个策略都 `supports` 同一 URL 时怎么办？ |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 🤖 AI 协同升级 |
||||
|
|
||||
|
### 架构审计师（必做） |
||||
|
|
||||
|
- 画出类依赖图 |
||||
|
- 发给 AI：“检查开闭原则达成度，Repository 封装完备性，是否存在循环依赖” |
||||
|
|
||||
|
### 进阶探究 |
||||
|
|
||||
|
- 不用工厂，直接用 `Map<String, CrawlStrategy>` 存起来 vs `StrategyFactory` 的区别？ |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 📚 总结 |
||||
|
|
||||
|
- ✅ 策略模式：算法可插拔，新增网站零痛苦 |
||||
|
- ✅ 工厂：自动匹配，URL → 策略的魔法 |
||||
|
- ✅ Repository：数据守卫，规则从口头约定变成代码强制 |
||||
|
- ✅ 架构：从“分开”到“优雅合上”，对扩展开放，对修改关闭 |
||||
|
|
||||
|
### W11 预告 |
||||
|
|
||||
|
自定义异常体系 + 日志 + 重试机制 |
||||
|
|
||||
|
> 🚀 让我们造的爬虫，经得住现实的考验 |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 谢谢！ |
||||
|
|
||||
|
**保持工程洁癖，下周见！** |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
# 居中标题 |
||||
|
|
||||
|
## 居中副标题 |
||||
|
|
||||
|
### 居中内容 |
||||
|
|
||||
|
--- |
||||
@ -0,0 +1,57 @@ |
|||||
|
<project xmlns="http://maven.apache.org/POM/4.0.0" |
||||
|
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" |
||||
|
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> |
||||
|
<modelVersion>4.0.0</modelVersion> |
||||
|
<groupId>com.example</groupId> |
||||
|
<artifactId>datacollect-cli</artifactId> |
||||
|
<version>0.1.0</version> |
||||
|
<properties> |
||||
|
<maven.compiler.source>11</maven.compiler.source> |
||||
|
<maven.compiler.target>11</maven.compiler.target> |
||||
|
</properties> |
||||
|
<dependencies> |
||||
|
<dependency> |
||||
|
<groupId>org.jsoup</groupId> |
||||
|
<artifactId>jsoup</artifactId> |
||||
|
<version>1.17.2</version> |
||||
|
</dependency> |
||||
|
<dependency> |
||||
|
<groupId>ch.qos.logback</groupId> |
||||
|
<artifactId>logback-classic</artifactId> |
||||
|
<version>1.4.11</version> |
||||
|
</dependency> |
||||
|
</dependencies> |
||||
|
<build> |
||||
|
<plugins> |
||||
|
<plugin> |
||||
|
<groupId>org.apache.maven.plugins</groupId> |
||||
|
<artifactId>maven-compiler-plugin</artifactId> |
||||
|
<version>3.8.1</version> |
||||
|
</plugin> |
||||
|
<plugin> |
||||
|
<groupId>org.apache.maven.plugins</groupId> |
||||
|
<artifactId>maven-assembly-plugin</artifactId> |
||||
|
<version>3.3.0</version> |
||||
|
<configuration> |
||||
|
<archive> |
||||
|
<manifest> |
||||
|
<mainClass>com.example.datacollect.Main</mainClass> |
||||
|
</manifest> |
||||
|
</archive> |
||||
|
<descriptorRefs> |
||||
|
<descriptorRef>jar-with-dependencies</descriptorRef> |
||||
|
</descriptorRefs> |
||||
|
</configuration> |
||||
|
<executions> |
||||
|
<execution> |
||||
|
<id>make-assembly</id> |
||||
|
<phase>package</phase> |
||||
|
<goals> |
||||
|
<goal>single</goal> |
||||
|
</goals> |
||||
|
</execution> |
||||
|
</executions> |
||||
|
</plugin> |
||||
|
</plugins> |
||||
|
</build> |
||||
|
</project> |
||||
@ -0,0 +1,113 @@ |
|||||
|
package com.example.datacollect; |
||||
|
|
||||
|
import com.example.datacollect.controller.CrawlerController; |
||||
|
import com.example.datacollect.exception.ParseException; |
||||
|
import com.example.datacollect.model.Article; |
||||
|
import com.example.datacollect.repository.ArticleRepository; |
||||
|
import com.example.datacollect.strategy.CrawlStrategy; |
||||
|
import com.example.datacollect.strategy.StrategyFactory; |
||||
|
import com.example.datacollect.view.ConsoleView; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
public class Main { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(Main.class); |
||||
|
|
||||
|
public static void main(String[] args) { |
||||
|
logger.info("Starting CLI Crawler application"); |
||||
|
|
||||
|
ConsoleView view = new ConsoleView(); |
||||
|
ArticleRepository repository = new ArticleRepository(); |
||||
|
StrategyFactory strategyFactory = new StrategyFactory(); |
||||
|
|
||||
|
if (args.length > 0 && "-test".equals(args[0])) { |
||||
|
logger.info("Running in test mode"); |
||||
|
runTest(view, repository, strategyFactory); |
||||
|
return; |
||||
|
} |
||||
|
|
||||
|
CrawlerController controller = new CrawlerController(view, repository, strategyFactory); |
||||
|
|
||||
|
view.printSuccess("Welcome to CLI Crawler (w10_3)! Type help for commands."); |
||||
|
logger.info("Application ready, waiting for input"); |
||||
|
|
||||
|
while (true) { |
||||
|
controller.handle(view.readLine()); |
||||
|
} |
||||
|
} |
||||
|
|
||||
|
private static void runTest(ConsoleView view, ArticleRepository repository, StrategyFactory strategyFactory) { |
||||
|
strategyFactory.register(new MockStrategy()); |
||||
|
|
||||
|
CrawlerController controller = new CrawlerController(view, repository, strategyFactory); |
||||
|
|
||||
|
view.printSuccess("=== 测试完整 crawl → list 流程 ==="); |
||||
|
|
||||
|
view.printInfo("\n1. 测试空列表状态:"); |
||||
|
controller.handle("list"); |
||||
|
|
||||
|
view.printInfo("\n2. 测试无效 URL（无匹配策略）:"); |
||||
|
controller.handle("crawl https://unknown.example.com"); |
||||
|
|
||||
|
view.printInfo("\n3. 测试爬取 mock.example.com:"); |
||||
|
controller.handle("crawl https://mock.example.com"); |
||||
|
|
||||
|
view.printInfo("\n4. 测试 list 显示爬取结果:"); |
||||
|
controller.handle("list"); |
||||
|
|
||||
|
view.printInfo("\n5. 测试爬取 blog.example.com:"); |
||||
|
controller.handle("crawl https://blog.example.com"); |
||||
|
|
||||
|
view.printInfo("\n6. 测试 list 显示累计结果:"); |
||||
|
controller.handle("list"); |
||||
|
|
||||
|
view.printInfo("\n7. 测试 getAll() 返回不可修改视图:"); |
||||
|
testUnmodifiableView(repository); |
||||
|
|
||||
|
view.printInfo("\n8. 测试 Repository 防御检查:"); |
||||
|
testRepositoryDefense(repository); |
||||
|
|
||||
|
view.printSuccess("\n=== 测试完成 ==="); |
||||
|
} |
||||
|
|
||||
|
private static void testUnmodifiableView(ArticleRepository repository) { |
||||
|
try { |
||||
|
repository.getAll().add(new Article("Test", "http://test.com", "")); |
||||
|
System.out.println("ERROR: 应该抛出 UnsupportedOperationException"); |
||||
|
} catch (UnsupportedOperationException e) { |
||||
|
System.out.println("SUCCESS: getAll() 返回不可修改视图，正确抛出异常"); |
||||
|
} |
||||
|
} |
||||
|
|
||||
|
private static void testRepositoryDefense(ArticleRepository repository) { |
||||
|
try { |
||||
|
repository.add(null); |
||||
|
System.out.println("ERROR: 应该抛出 NullPointerException"); |
||||
|
} catch (NullPointerException e) { |
||||
|
System.out.println("SUCCESS: 添加 null 文章正确抛出异常"); |
||||
|
} |
||||
|
|
||||
|
try { |
||||
|
repository.add(new Article("", "http://test.com", "")); |
||||
|
System.out.println("ERROR: 应该抛出 IllegalArgumentException"); |
||||
|
} catch (IllegalArgumentException e) { |
||||
|
System.out.println("SUCCESS: 添加空标题文章正确抛出异常"); |
||||
|
} |
||||
|
} |
||||
|
|
||||
|
public static class MockStrategy implements CrawlStrategy { |
||||
|
@Override |
||||
|
public boolean supports(String url) { |
||||
|
return url != null && url.contains("mock.example.com"); |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public java.util.List<Article> parse(String url, org.jsoup.nodes.Document doc) throws ParseException { |
||||
|
java.util.List<Article> articles = new java.util.ArrayList<>(); |
||||
|
articles.add(new Article("模拟文章 1", url + "/article1", "模拟内容 1")); |
||||
|
articles.add(new Article("模拟文章 2", url + "/article2", "模拟内容 2")); |
||||
|
articles.add(new Article("模拟文章 3", url + "/article3", "模拟内容 3")); |
||||
|
return articles; |
||||
|
} |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,8 @@ |
|||||
|
package com.example.datacollect.command; |
||||
|
|
||||
|
import com.example.datacollect.repository.ArticleRepository; |
||||
|
|
||||
|
public interface Command { |
||||
|
String getName(); |
||||
|
void execute(String[] args, ArticleRepository repository); |
||||
|
} |
||||
@ -0,0 +1,96 @@ |
|||||
|
package com.example.datacollect.command; |
||||
|
|
||||
|
import com.example.datacollect.exception.ParseException; |
||||
|
import com.example.datacollect.repository.ArticleRepository; |
||||
|
import com.example.datacollect.strategy.CrawlStrategy; |
||||
|
import com.example.datacollect.strategy.StrategyFactory; |
||||
|
import com.example.datacollect.view.ConsoleView; |
||||
|
import org.jsoup.Jsoup; |
||||
|
import org.jsoup.nodes.Document; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
public class CrawlCommand implements Command { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(CrawlCommand.class); |
||||
|
private static final int MAX_RETRY = 3; |
||||
|
private static final long RETRY_DELAY_MS = 1000; |
||||
|
|
||||
|
private final ConsoleView view; |
||||
|
private final StrategyFactory strategyFactory; |
||||
|
|
||||
|
public CrawlCommand(ConsoleView view, StrategyFactory strategyFactory) { |
||||
|
this.view = view; |
||||
|
this.strategyFactory = strategyFactory; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public String getName() { |
||||
|
return "crawl"; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public void execute(String[] args, ArticleRepository repository) { |
||||
|
if (args.length < 2) { |
||||
|
String errorMsg = "Usage: crawl <url>"; |
||||
|
logger.warn(errorMsg); |
||||
|
view.printError(errorMsg); |
||||
|
return; |
||||
|
} |
||||
|
String url = args[1]; |
||||
|
logger.info("Crawl started for: {}", url); |
||||
|
|
||||
|
CrawlStrategy strategy = strategyFactory.getStrategy(url); |
||||
|
if (strategy == null) { |
||||
|
String errorMsg = "No strategy found for: " + url; |
||||
|
logger.warn(errorMsg); |
||||
|
view.printError(errorMsg); |
||||
|
return; |
||||
|
} |
||||
|
|
||||
|
logger.info("Starting crawl for URL: {}", url); |
||||
|
view.printInfo("Crawling: " + url); |
||||
|
|
||||
|
Document doc = null; |
||||
|
int attempt = 0; |
||||
|
boolean success = false; |
||||
|
|
||||
|
while (attempt < MAX_RETRY && !success) { |
||||
|
attempt++; |
||||
|
try { |
||||
|
logger.debug("Attempt {} to fetch URL: {}", attempt, url); |
||||
|
doc = Jsoup.connect(url).get(); |
||||
|
success = true; |
||||
|
} catch (Exception e) { |
||||
|
logger.warn("Attempt {} failed for URL {}: {}", attempt, url, e.getMessage()); |
||||
|
if (attempt < MAX_RETRY) { |
||||
|
logger.info("Retrying in {}ms...", RETRY_DELAY_MS); |
||||
|
try { |
||||
|
Thread.sleep(RETRY_DELAY_MS); |
||||
|
} catch (InterruptedException ie) { |
||||
|
Thread.currentThread().interrupt(); |
||||
|
break; |
||||
|
} |
||||
|
} |
||||
|
} |
||||
|
} |
||||
|
|
||||
|
if (!success) { |
||||
|
String errorMsg = "Failed to fetch URL after " + MAX_RETRY + " attempts: " + url; |
||||
|
logger.error(errorMsg); |
||||
|
view.printError(errorMsg); |
||||
|
return; |
||||
|
} |
||||
|
|
||||
|
try { |
||||
|
var articles = strategy.parse(url, doc); |
||||
|
for (var article : articles) { |
||||
|
repository.add(article); |
||||
|
} |
||||
|
logger.info("Successfully crawled {} articles from {}", articles.size(), url); |
||||
|
view.printSuccess("Crawled " + articles.size() + " articles."); |
||||
|
} catch (ParseException e) { |
||||
|
logger.error("Parse error for URL {}: {}", url, e.getMessage(), e); |
||||
|
view.printError("Parse error: " + e.getMessage()); |
||||
|
} |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,28 @@ |
|||||
|
package com.example.datacollect.command; |
||||
|
|
||||
|
import com.example.datacollect.repository.ArticleRepository; |
||||
|
import com.example.datacollect.view.ConsoleView; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
public class ExitCommand implements Command { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(ExitCommand.class); |
||||
|
|
||||
|
private final ConsoleView view; |
||||
|
|
||||
|
public ExitCommand(ConsoleView view) { |
||||
|
this.view = view; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public String getName() { |
||||
|
return "exit"; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public void execute(String[] args, ArticleRepository repository) { |
||||
|
logger.info("Exiting application"); |
||||
|
view.printSuccess("Bye!"); |
||||
|
System.exit(0); |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,27 @@ |
|||||
|
package com.example.datacollect.command; |
||||
|
|
||||
|
import com.example.datacollect.repository.ArticleRepository; |
||||
|
import com.example.datacollect.view.ConsoleView; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
public class HelpCommand implements Command { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(HelpCommand.class); |
||||
|
|
||||
|
private final ConsoleView view; |
||||
|
|
||||
|
public HelpCommand(ConsoleView view) { |
||||
|
this.view = view; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public String getName() { |
||||
|
return "help"; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public void execute(String[] args, ArticleRepository repository) { |
||||
|
logger.debug("Displaying help"); |
||||
|
view.printInfo("Commands: crawl <url>, list, help, exit"); |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,27 @@ |
|||||
|
package com.example.datacollect.command; |
||||
|
|
||||
|
import com.example.datacollect.repository.ArticleRepository; |
||||
|
import com.example.datacollect.view.ConsoleView; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
public class ListCommand implements Command { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(ListCommand.class); |
||||
|
|
||||
|
private final ConsoleView view; |
||||
|
|
||||
|
public ListCommand(ConsoleView view) { |
||||
|
this.view = view; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public String getName() { |
||||
|
return "list"; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public void execute(String[] args, ArticleRepository repository) { |
||||
|
logger.debug("Listing articles"); |
||||
|
view.display(repository.getAll()); |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,57 @@ |
|||||
|
package com.example.datacollect.controller; |
||||
|
|
||||
|
import com.example.datacollect.command.Command; |
||||
|
import com.example.datacollect.command.CrawlCommand; |
||||
|
import com.example.datacollect.command.ExitCommand; |
||||
|
import com.example.datacollect.command.HelpCommand; |
||||
|
import com.example.datacollect.command.ListCommand; |
||||
|
import com.example.datacollect.repository.ArticleRepository; |
||||
|
import com.example.datacollect.strategy.StrategyFactory; |
||||
|
import com.example.datacollect.view.ConsoleView; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
import java.util.HashMap; |
||||
|
import java.util.Map; |
||||
|
|
||||
|
public class CrawlerController { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(CrawlerController.class); |
||||
|
|
||||
|
private final Map<String, Command> commands = new HashMap<>(); |
||||
|
private final ConsoleView view; |
||||
|
private final ArticleRepository repository; |
||||
|
|
||||
|
public CrawlerController(ConsoleView view, ArticleRepository repository, StrategyFactory strategyFactory) { |
||||
|
this.view = view; |
||||
|
this.repository = repository; |
||||
|
register(new HelpCommand(view)); |
||||
|
register(new ListCommand(view)); |
||||
|
register(new CrawlCommand(view, strategyFactory)); |
||||
|
register(new ExitCommand(view)); |
||||
|
logger.info("CrawlerController initialized with {} commands", commands.size()); |
||||
|
} |
||||
|
|
||||
|
private void register(Command command) { |
||||
|
commands.put(command.getName(), command); |
||||
|
logger.debug("Registered command: {}", command.getName()); |
||||
|
} |
||||
|
|
||||
|
public void handle(String input) { |
||||
|
String text = input == null ? "" : input.trim(); |
||||
|
if (text.isEmpty()) { |
||||
|
return; |
||||
|
} |
||||
|
|
||||
|
String[] args = text.split("\\s+"); |
||||
|
String cmdName = args[0].toLowerCase(); |
||||
|
Command command = commands.get(cmdName); |
||||
|
if (command == null) { |
||||
|
String errorMsg = "Unknown command: " + cmdName; |
||||
|
logger.warn(errorMsg); |
||||
|
view.printError(errorMsg); |
||||
|
return; |
||||
|
} |
||||
|
logger.debug("Executing command: {}", cmdName); |
||||
|
command.execute(args, repository); |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,11 @@ |
|||||
|
package com.example.datacollect.exception; |
||||
|
|
||||
|
public class CrawlerException extends Exception { |
||||
|
public CrawlerException(String message) { |
||||
|
super(message); |
||||
|
} |
||||
|
|
||||
|
public CrawlerException(String message, Throwable cause) { |
||||
|
super(message, cause); |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,11 @@ |
|||||
|
package com.example.datacollect.exception; |
||||
|
|
||||
|
public class NetworkException extends CrawlerException { |
||||
|
public NetworkException(String message) { |
||||
|
super(message); |
||||
|
} |
||||
|
|
||||
|
public NetworkException(String message, Throwable cause) { |
||||
|
super(message, cause); |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,11 @@ |
|||||
|
package com.example.datacollect.exception; |
||||
|
|
||||
|
public class ParseException extends CrawlerException { |
||||
|
public ParseException(String message) { |
||||
|
super(message); |
||||
|
} |
||||
|
|
||||
|
public ParseException(String message, Throwable cause) { |
||||
|
super(message, cause); |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,45 @@ |
|||||
|
package com.example.datacollect.model; |
||||
|
|
||||
|
public class Article { |
||||
|
private String title; |
||||
|
private String url; |
||||
|
private String content; |
||||
|
|
||||
|
public Article(String title, String url, String content) { |
||||
|
this.title = title; |
||||
|
this.url = url; |
||||
|
this.content = content; |
||||
|
} |
||||
|
|
||||
|
public String getTitle() { |
||||
|
return title; |
||||
|
} |
||||
|
|
||||
|
public void setTitle(String title) { |
||||
|
this.title = title; |
||||
|
} |
||||
|
|
||||
|
public String getUrl() { |
||||
|
return url; |
||||
|
} |
||||
|
|
||||
|
public void setUrl(String url) { |
||||
|
this.url = url; |
||||
|
} |
||||
|
|
||||
|
public String getContent() { |
||||
|
return content; |
||||
|
} |
||||
|
|
||||
|
public void setContent(String content) { |
||||
|
this.content = content; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public String toString() { |
||||
|
return "Article{" |
||||
|
+ "title='" + title + '\'' |
||||
|
+ ", url='" + url + '\'' |
||||
|
+ '}'; |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,80 @@ |
|||||
|
package com.example.datacollect.repository; |
||||
|
|
||||
|
import com.example.datacollect.model.Article; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
import java.util.ArrayList; |
||||
|
import java.util.Collections; |
||||
|
import java.util.List; |
||||
|
import java.util.Objects; |
||||
|
|
||||
|
public class ArticleRepository { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(ArticleRepository.class); |
||||
|
|
||||
|
private final List<Article> articles = new ArrayList<>(); |
||||
|
|
||||
|
public void add(Article article) { |
||||
|
Objects.requireNonNull(article, "Article cannot be null"); |
||||
|
|
||||
|
if (article.getTitle() == null || article.getTitle().trim().isEmpty()) { |
||||
|
logger.warn("Attempted to add article with empty title"); |
||||
|
throw new IllegalArgumentException("Article title cannot be null or empty"); |
||||
|
} |
||||
|
|
||||
|
if (article.getUrl() == null || article.getUrl().trim().isEmpty()) { |
||||
|
logger.warn("Attempted to add article with empty URL"); |
||||
|
throw new IllegalArgumentException("Article URL cannot be null or empty"); |
||||
|
} |
||||
|
|
||||
|
articles.add(article); |
||||
|
logger.debug("Added article: {}", article.getTitle()); |
||||
|
} |
||||
|
|
||||
|
public void addAll(List<Article> articleList) { |
||||
|
Objects.requireNonNull(articleList, "Article list cannot be null"); |
||||
|
|
||||
|
if (articleList.isEmpty()) { |
||||
|
logger.debug("Empty article list provided, nothing to add"); |
||||
|
return; |
||||
|
} |
||||
|
|
||||
|
for (Article article : articleList) { |
||||
|
add(article); |
||||
|
} |
||||
|
logger.info("Added {} articles", articleList.size()); |
||||
|
} |
||||
|
|
||||
|
public List<Article> getAll() { |
||||
|
List<Article> result = Collections.unmodifiableList(articles); |
||||
|
logger.debug("Returning {} articles (unmodifiable)", result.size()); |
||||
|
return result; |
||||
|
} |
||||
|
|
||||
|
public Article get(int index) { |
||||
|
if (index < 0 || index >= articles.size()) { |
||||
|
logger.warn("Index out of bounds: {} (size: {})", index, articles.size()); |
||||
|
throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + articles.size()); |
||||
|
} |
||||
|
return articles.get(index); |
||||
|
} |
||||
|
|
||||
|
public int size() { |
||||
|
return articles.size(); |
||||
|
} |
||||
|
|
||||
|
public boolean isEmpty() { |
||||
|
return articles.isEmpty(); |
||||
|
} |
||||
|
|
||||
|
public void clear() { |
||||
|
int size = articles.size(); |
||||
|
articles.clear(); |
||||
|
logger.info("Cleared {} articles", size); |
||||
|
} |
||||
|
|
||||
|
public boolean contains(Article article) { |
||||
|
Objects.requireNonNull(article, "Article cannot be null"); |
||||
|
return articles.contains(article); |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,43 @@ |
|||||
|
package com.example.datacollect.strategy; |
||||
|
|
||||
|
import com.example.datacollect.exception.ParseException; |
||||
|
import com.example.datacollect.model.Article; |
||||
|
import org.jsoup.nodes.Document; |
||||
|
import org.jsoup.nodes.Element; |
||||
|
import org.jsoup.select.Elements; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
import java.util.ArrayList; |
||||
|
import java.util.List; |
||||
|
|
||||
|
public class BlogStrategy implements CrawlStrategy { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(BlogStrategy.class); |
||||
|
|
||||
|
@Override |
||||
|
public boolean supports(String url) { |
||||
|
boolean supported = url != null && url.contains("blog.example.com"); |
||||
|
logger.debug("BlogStrategy supports URL {}: {}", url, supported); |
||||
|
return supported; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public List<Article> parse(String url, Document doc) throws ParseException { |
||||
|
try { |
||||
|
logger.debug("Parsing blog page: {}", url); |
||||
|
List<Article> articles = new ArrayList<>(); |
||||
|
Elements titles = doc.select(".post-title"); |
||||
|
logger.debug("Found {} titles", titles.size()); |
||||
|
|
||||
|
for (Element e : titles) { |
||||
|
articles.add(new Article(e.text(), url, "")); |
||||
|
} |
||||
|
|
||||
|
logger.info("Parsed {} articles from blog", articles.size()); |
||||
|
return articles; |
||||
|
} catch (Exception e) { |
||||
|
logger.error("Failed to parse blog page: {}", e.getMessage(), e); |
||||
|
throw new ParseException("Failed to parse blog page", e); |
||||
|
} |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,12 @@ |
|||||
|
package com.example.datacollect.strategy; |
||||
|
|
||||
|
import com.example.datacollect.exception.ParseException; |
||||
|
import com.example.datacollect.model.Article; |
||||
|
import org.jsoup.nodes.Document; |
||||
|
|
||||
|
import java.util.List; |
||||
|
|
||||
|
public interface CrawlStrategy { |
||||
|
List<Article> parse(String url, Document doc) throws ParseException; |
||||
|
boolean supports(String url); |
||||
|
} |
||||
@ -0,0 +1,65 @@ |
|||||
|
package com.example.datacollect.strategy; |
||||
|
|
||||
|
import com.example.datacollect.exception.ParseException; |
||||
|
import com.example.datacollect.model.Article; |
||||
|
import org.jsoup.nodes.Document; |
||||
|
import org.jsoup.nodes.Element; |
||||
|
import org.jsoup.select.Elements; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
import java.util.ArrayList; |
||||
|
import java.util.List; |
||||
|
|
||||
|
public class HnuNewsStrategy implements CrawlStrategy { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(HnuNewsStrategy.class); |
||||
|
|
||||
|
@Override |
||||
|
public boolean supports(String url) { |
||||
|
boolean supported = url != null && url.contains("news.hnu.edu.cn"); |
||||
|
logger.debug("HnuNewsStrategy supports URL {}: {}", url, supported); |
||||
|
return supported; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public List<Article> parse(String url, Document doc) throws ParseException { |
||||
|
try { |
||||
|
logger.debug("Parsing Hnu news page: {}", url); |
||||
|
List<Article> articles = new ArrayList<>(); |
||||
|
Elements listItems = doc.select("ul.list11 li"); |
||||
|
logger.debug("Found {} list items", listItems.size()); |
||||
|
|
||||
|
for (Element li : listItems) { |
||||
|
Element link = li.selectFirst("a"); |
||||
|
if (link == null) continue; |
||||
|
|
||||
|
String articleUrl = link.attr("href"); |
||||
|
if (!articleUrl.startsWith("http")) { |
||||
|
articleUrl = "https://news.hnu.edu.cn" + articleUrl.replace("..", ""); |
||||
|
} |
||||
|
|
||||
|
String title = ""; |
||||
|
Element titleEl = link.selectFirst("h4.l2.h4s2"); |
||||
|
if (titleEl != null) { |
||||
|
title = titleEl.text().trim(); |
||||
|
} |
||||
|
|
||||
|
String content = ""; |
||||
|
Element contentEl = link.selectFirst("p.l3.ps3"); |
||||
|
if (contentEl != null) { |
||||
|
content = contentEl.text().trim(); |
||||
|
} |
||||
|
|
||||
|
if (!title.isEmpty()) { |
||||
|
articles.add(new Article(title, articleUrl, content)); |
||||
|
} |
||||
|
} |
||||
|
|
||||
|
logger.info("Parsed {} articles from Hnu news", articles.size()); |
||||
|
return articles; |
||||
|
} catch (Exception e) { |
||||
|
logger.error("Failed to parse Hnu news page: {}", e.getMessage(), e); |
||||
|
throw new ParseException("Failed to parse Hnu news page", e); |
||||
|
} |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,43 @@ |
|||||
|
package com.example.datacollect.strategy; |
||||
|
|
||||
|
import com.example.datacollect.exception.ParseException; |
||||
|
import com.example.datacollect.model.Article; |
||||
|
import org.jsoup.nodes.Document; |
||||
|
import org.jsoup.nodes.Element; |
||||
|
import org.jsoup.select.Elements; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
import java.util.ArrayList; |
||||
|
import java.util.List; |
||||
|
|
||||
|
public class NewsStrategy implements CrawlStrategy { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(NewsStrategy.class); |
||||
|
|
||||
|
@Override |
||||
|
public boolean supports(String url) { |
||||
|
boolean supported = url != null && url.contains("news.example.com"); |
||||
|
logger.debug("NewsStrategy supports URL {}: {}", url, supported); |
||||
|
return supported; |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public List<Article> parse(String url, Document doc) throws ParseException { |
||||
|
try { |
||||
|
logger.debug("Parsing news page: {}", url); |
||||
|
List<Article> articles = new ArrayList<>(); |
||||
|
Elements items = doc.select(".article-headline"); |
||||
|
logger.debug("Found {} headlines", items.size()); |
||||
|
|
||||
|
for (Element e : items) { |
||||
|
articles.add(new Article(e.text(), url, "")); |
||||
|
} |
||||
|
|
||||
|
logger.info("Parsed {} articles from news", articles.size()); |
||||
|
return articles; |
||||
|
} catch (Exception e) { |
||||
|
logger.error("Failed to parse news page: {}", e.getMessage(), e); |
||||
|
throw new ParseException("Failed to parse news page", e); |
||||
|
} |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,55 @@ |
|||||
|
package com.example.datacollect.strategy; |
||||
|
|
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
import java.util.ArrayList; |
||||
|
import java.util.List; |
||||
|
import java.util.Objects; |
||||
|
|
||||
|
public class StrategyFactory { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(StrategyFactory.class); |
||||
|
|
||||
|
private final List<CrawlStrategy> strategies = new ArrayList<>(); |
||||
|
|
||||
|
public StrategyFactory() { |
||||
|
strategies.add(new HnuNewsStrategy()); |
||||
|
strategies.add(new BlogStrategy()); |
||||
|
strategies.add(new NewsStrategy()); |
||||
|
logger.info("StrategyFactory initialized with {} strategies", strategies.size()); |
||||
|
} |
||||
|
|
||||
|
public CrawlStrategy getStrategy(String url) { |
||||
|
Objects.requireNonNull(url, "URL cannot be null"); |
||||
|
|
||||
|
if (url.trim().isEmpty()) { |
||||
|
logger.warn("Empty URL provided"); |
||||
|
return null; |
||||
|
} |
||||
|
|
||||
|
for (CrawlStrategy s : strategies) { |
||||
|
if (s.supports(url)) { |
||||
|
logger.debug("Found strategy {} for URL: {}", s.getClass().getSimpleName(), url); |
||||
|
return s; |
||||
|
} |
||||
|
} |
||||
|
logger.warn("No strategy found for URL: {}", url); |
||||
|
return null; |
||||
|
} |
||||
|
|
||||
|
public void register(CrawlStrategy strategy) { |
||||
|
Objects.requireNonNull(strategy, "Strategy cannot be null"); |
||||
|
|
||||
|
if (strategies.contains(strategy)) { |
||||
|
logger.warn("Strategy {} already registered", strategy.getClass().getSimpleName()); |
||||
|
return; |
||||
|
} |
||||
|
|
||||
|
strategies.add(strategy); |
||||
|
logger.info("Registered strategy: {}", strategy.getClass().getSimpleName()); |
||||
|
} |
||||
|
|
||||
|
public int getStrategyCount() { |
||||
|
return strategies.size(); |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,52 @@ |
|||||
|
package com.example.datacollect.view; |
||||
|
|
||||
|
import com.example.datacollect.model.Article; |
||||
|
import org.slf4j.Logger; |
||||
|
import org.slf4j.LoggerFactory; |
||||
|
|
||||
|
import java.util.List; |
||||
|
import java.util.Scanner; |
||||
|
|
||||
|
public class ConsoleView { |
||||
|
private static final Logger logger = LoggerFactory.getLogger(ConsoleView.class); |
||||
|
|
||||
|
private static final String ANSI_RESET = "\u001B[0m"; |
||||
|
private static final String ANSI_GREEN = "\u001B[32m"; |
||||
|
private static final String ANSI_RED = "\u001B[31m"; |
||||
|
private static final String ANSI_BLUE = "\u001B[34m"; |
||||
|
|
||||
|
private final Scanner scanner = new Scanner(System.in); |
||||
|
|
||||
|
public String readLine() { |
||||
|
logger.debug("Reading input from console"); |
||||
|
System.out.print("> "); |
||||
|
return scanner.nextLine(); |
||||
|
} |
||||
|
|
||||
|
public void printSuccess(String msg) { |
||||
|
logger.info("Success: {}", msg); |
||||
|
System.out.println(ANSI_GREEN + msg + ANSI_RESET); |
||||
|
} |
||||
|
|
||||
|
public void printError(String msg) { |
||||
|
logger.error("Error: {}", msg); |
||||
|
System.out.println(ANSI_RED + msg + ANSI_RESET); |
||||
|
} |
||||
|
|
||||
|
public void printInfo(String msg) { |
||||
|
logger.debug("Info: {}", msg); |
||||
|
System.out.println(ANSI_BLUE + msg + ANSI_RESET); |
||||
|
} |
||||
|
|
||||
|
public void display(List<Article> articles) { |
||||
|
logger.debug("Displaying {} articles", articles.size()); |
||||
|
if (articles.isEmpty()) { |
||||
|
printInfo("暂无文章，请先执行 crawl。"); |
||||
|
return; |
||||
|
} |
||||
|
for (int i = 0; i < articles.size(); i++) { |
||||
|
Article a = articles.get(i); |
||||
|
System.out.println((i + 1) + ". " + a.getTitle() + " | " + a.getUrl()); |
||||
|
} |
||||
|
} |
||||
|
} |
||||
@ -0,0 +1,27 @@ |
|||||
|
<configuration> |
||||
|
<property name="LOG_PATH" value="./logs"/> |
||||
|
|
||||
|
<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender"> |
||||
|
<encoder> |
||||
|
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern> |
||||
|
</encoder> |
||||
|
</appender> |
||||
|
|
||||
|
<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender"> |
||||
|
<file>${LOG_PATH}/crawler.log</file> |
||||
|
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy"> |
||||
|
<fileNamePattern>${LOG_PATH}/crawler.%d{yyyy-MM-dd}.log</fileNamePattern> |
||||
|
<maxHistory>30</maxHistory> |
||||
|
</rollingPolicy> |
||||
|
<encoder> |
||||
|
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern> |
||||
|
</encoder> |
||||
|
</appender> |
||||
|
|
||||
|
<logger name="com.example.datacollect" level="DEBUG"/> |
||||
|
|
||||
|
<root level="INFO"> |
||||
|
<appender-ref ref="CONSOLE"/> |
||||
|
<appender-ref ref="FILE"/> |
||||
|
</root> |
||||
|
</configuration> |
||||
@ -0,0 +1,27 @@ |
|||||
|
<configuration> |
||||
|
<property name="LOG_PATH" value="./logs"/> |
||||
|
|
||||
|
<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender"> |
||||
|
<encoder> |
||||
|
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern> |
||||
|
</encoder> |
||||
|
</appender> |
||||
|
|
||||
|
<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender"> |
||||
|
<file>${LOG_PATH}/crawler.log</file> |
||||
|
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy"> |
||||
|
<fileNamePattern>${LOG_PATH}/crawler.%d{yyyy-MM-dd}.log</fileNamePattern> |
||||
|
<maxHistory>30</maxHistory> |
||||
|
</rollingPolicy> |
||||
|
<encoder> |
||||
|
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern> |
||||
|
</encoder> |
||||
|
</appender> |
||||
|
|
||||
|
<logger name="com.example.datacollect" level="DEBUG"/> |
||||
|
|
||||
|
<root level="INFO"> |
||||
|
<appender-ref ref="CONSOLE"/> |
||||
|
<appender-ref ref="FILE"/> |
||||
|
</root> |
||||
|
</configuration> |
||||
@ -0,0 +1,3 @@ |
|||||
|
artifactId=datacollect-cli |
||||
|
groupId=com.example |
||||
|
version=0.1.0 |
||||
@ -0,0 +1,19 @@ |
|||||
|
com\example\datacollect\command\ListCommand.class |
||||
|
com\example\datacollect\command\CrawlCommand.class |
||||
|
com\example\datacollect\strategy\BlogStrategy.class |
||||
|
com\example\datacollect\repository\ArticleRepository.class |
||||
|
com\example\datacollect\Main.class |
||||
|
com\example\datacollect\view\ConsoleView.class |
||||
|
com\example\datacollect\command\ExitCommand.class |
||||
|
com\example\datacollect\command\HelpCommand.class |
||||
|
com\example\datacollect\Main$MockStrategy.class |
||||
|
com\example\datacollect\strategy\NewsStrategy.class |
||||
|
com\example\datacollect\command\Command.class |
||||
|
com\example\datacollect\controller\CrawlerController.class |
||||
|
com\example\datacollect\exception\CrawlerException.class |
||||
|
com\example\datacollect\exception\NetworkException.class |
||||
|
com\example\datacollect\strategy\StrategyFactory.class |
||||
|
com\example\datacollect\strategy\HnuNewsStrategy.class |
||||
|
com\example\datacollect\exception\ParseException.class |
||||
|
com\example\datacollect\strategy\CrawlStrategy.class |
||||
|
com\example\datacollect\model\Article.class |
||||
@ -0,0 +1,18 @@ |
|||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\strategy\StrategyFactory.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\exception\CrawlerException.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\strategy\BlogStrategy.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\Main.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\repository\ArticleRepository.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\command\ExitCommand.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\strategy\CrawlStrategy.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\exception\ParseException.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\strategy\HnuNewsStrategy.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\command\CrawlCommand.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\command\ListCommand.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\view\ConsoleView.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\exception\NetworkException.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\strategy\NewsStrategy.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\model\Article.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\controller\CrawlerController.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\command\HelpCommand.java |
||||
|
D:\java1\java-cli\src\main\java\com\example\datacollect\command\Command.java |
||||
@ -0,0 +1,705 @@ |
|||||
|
# 教案：《高级程序设计》第10周——设计模式：灵活性与可扩展性 |
||||
|
|
||||
|
| 项目 | 内容 | |
||||
|
| -------- | ---------------------------------------------------------------------------- | |
||||
|
| **课程名称** | 高级程序设计 | |
||||
|
| **周次** | 第10周 | |
||||
|
| **主题** | 设计模式——灵活性与可扩展性 | |
||||
|
| **学时** | 2学时（90分钟） | |
||||
|
| **授课对象** | 已完成第9周CLI+MVC架构学习，具备Command模式基础 | |
||||
|
| **教学环境** | JDK 17+、IntelliJ IDEA、Maven | |
||||
|
| **前情提要** | W9搭建了CLI骨架：MVC分层 + Command路由，但留下了两大隐患——解析逻辑耦合在Command中、List\<Article\>共享引用裸奔 | |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 教学调整说明：为什么W10要在“骨架”上装“盔甲”？ |
||||
|
|
||||
|
> **W9成果**：一个可扩展的命令行骨架 → **W9痛点**：解析器与数据存储仍在“裸奔” |
||||
|
|
||||
|
| 维度 | W9状态 | W10目标 | |
||||
|
|------|--------|---------| |
||||
|
| **架构** | MVC分层清晰 | MVC + 策略模式 + 仓库层 | |
||||
|
| **命令扩展** | 新增命令不改Controller | 新增解析器不改任何旧代码 | |
||||
|
| **数据安全** | List\<Article\>全员可写 | Repository封装，只暴露安全接口 | |
||||
|
| **解析逻辑** | 硬编码在CrawlCommand内 | 策略模式，按URL自动匹配 | |
||||
|
| **代码量** | ~8个类 | ~12个类，但每个更小更纯粹 | |
||||
|
|
||||
|
**决策理由**： |
||||
|
1. W9学生已经感受到Command模式的好处——**多态带来的扩展性** |
||||
|
2. 策略模式是多态思想的又一次实战，是**接口抽象的深化** |
||||
|
3. 仓库层是“封装”这一OOP核心原则的落地，补上W9留下的课 |
||||
|
4. 解析器工厂让学生看到**“自动匹配”**的威力——增加网站支持只需新增一个类 |
||||
|
|
||||
|
**更深层的教育价值**： |
||||
|
> W9教会学生“怎么把代码分开”，W10要教会学生“怎么把代码分开后还能优雅地合上”——**接口即合同，工厂即自动匹配，仓库即数据守卫**。这三句话，就是本周的全部精华。 |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 一、教学目标 |
||||
|
|
||||
|
| 目标维度 | 具体描述 | |
||||
|
|----------|----------| |
||||
|
| **知识掌握** | 理解策略模式的定义与多态本质；掌握工厂模式的两类变体（工厂方法/简单工厂）及适用场景；理解仓库模式对数据访问的封装原理。 | |
||||
|
| **工程实践** | 能在爬虫项目中用策略模式封装不同网站的解析逻辑；能实现解析器工厂，根据URL自动匹配解析策略；能用Repository模式替代裸List，提供安全的数据访问接口。 | |
||||
|
| **思维转型** | 从“写死逻辑”转向“策略可插拔”；从“直接操作集合”转向“通过仓库存取”；理解“对扩展开放，对修改关闭”的开闭原则。 | |
||||
|
| **工具应用** | 利用AI审查策略模式实现是否真正解耦；让AI扮演“网站结构分析师”辅助编写具体解析策略；用AI生成Repository的安全接口建议。 | |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 二、教学重点与难点 |
||||
|
|
||||
|
| 项目 | 内容 | 突破方法 | |
||||
|
|------|------|----------| |
||||
|
| **重点** | 策略模式的多态本质、解析器工厂的自动匹配机制、Repository对数据访问的封装 | 以“新增网站需要改什么”为切入点，展示策略模式的开闭原则达成；通过“攻击”当前List裸奔的问题，引出Repository的必然性 | |
||||
|
| **难点** | 理解“接口即合同”的抽象思维、工厂模式中反射/Map注册的实现、仓库层与Strategy模式的协同 | 用“插座与电器”类比接口标准；现场演示从硬编码→工厂→反射的演进路径；用时序图展示“用户→Command→Strategy→Repository”的完整调用链 | |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 三、教学过程设计（90分钟） |
||||
|
|
||||
|
| 环节 | 时间 | 教学内容 | 师生活动 | AI协同点 | |
||||
|
| -------------------------- | --- | ----------------------------------------------------------------- | -------------------------------------- | --------------------------- | |
||||
|
| **1. W9回顾与痛点暴露** | 8' | 回顾W9成果（CLI骨架），暴露两大隐患：①CrawlCommand里解析逻辑硬编码；②List\<Article\>全员可读可写 | **教师演示**：展示W9代码，用“事故场景”引发思考 | — | |
||||
|
| **2. 策略模式：解析器的“插头标准化”** | 18' | 策略模式定义、接口设计、多态调用、与Command模式的对比 | **类比**：插座与电器；**教师演示**：从if-else到策略模式的演进 | 让AI生成“策略模式vs switch-case”对比 | |
||||
|
| **3. 解析器工厂：自动匹配的魔法** | 14' | 工厂模式的两种形态（简单工厂→Map注册工厂），解析器工厂实现 | **教师演示**：先用if-else判断host，再升级为Map注册工厂 | 让AI解释工厂模式与策略模式如何协同 | |
||||
|
| **4. Repository模式：武装数据访问** | 12' | Repository定义、接口设计、替换List\<Article\>后的影响 | **教师演示**：在原代码中把List替换为Repository，展示改动点 | 学生用AI审计Repository接口的“最小完备性” | |
||||
|
| **5. 整体架构串联** | 8' | 用一张时序图串联：用户→CLI→Controller→Command→Strategy→Repository→Model | **师生互动**：让学生在白板上画出调用链 | — | |
||||
|
| **6. 代码落地** | 20' | 实现CrawlStrategy接口 + 两个策略 + 解析器工厂 + ArticleRepository | **教师演示**：分步写出代码，刻意埋入“策略匹配失败”的异常处理 | 完成后用AI检查策略模式实现 | |
||||
|
| **7. 架构反思与W11预告** | 5' | 当前架构还有什么隐患？（异常处理不统一、日志缺失）→ 预告W11健壮性工程 | **师生互动**：如果解析器工厂找不到匹配策略，会发生什么？ | — | |
||||
|
| **8. 实践任务** | 5' | 实现策略模式和仓库层，完成本周代码升级 | 学生现场编码，教师巡视 | — | |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 四、核心教学内容脚本 |
||||
|
|
||||
|
### 4.1 W9回顾与痛点暴露（8分钟） |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "上节课我们搭了一个很漂亮的骨架——CLI+MVC+Command模式。我们先来表扬一下自己：新增一个命令，只要新建一个类，Controller零改动。但请大家想一个问题——" |
||||
|
|
||||
|
**投影展示W9的CrawlCommand存根**： |
||||
|
```java |
||||
|
public class CrawlCommand implements Command { |
||||
|
// ... |
||||
|
public void execute(String[] args, List<Article> articles) { |
||||
|
if (args.length < 2) { |
||||
|
view.printError("Usage: crawl <url>"); |
||||
|
return; |
||||
|
} |
||||
|
view.printInfo("Stub: Would crawl " + args[1]); |
||||
|
} |
||||
|
} |
||||
|
``` |
||||
|
|
||||
|
**提问引导**： |
||||
|
1. "这个存根下周要填坑了。假设我们现在要真正实现爬取，代码写在哪？" |
||||
|
2. "如果我要支持两个网站——比如一个技术博客和一个新闻网站——它们的HTML结构完全不一样，这个`execute`方法会变成什么样？" |
||||
|
|
||||
|
**展示“噩梦版”CrawlCommand**： |
||||
|
```java |
||||
|
public void execute(String[] args, List<Article> articles) { |
||||
|
String url = args[1]; |
||||
|
// 五十行if-else地狱... |
||||
|
if (url.contains("blog.example.com")) { |
||||
|
// 解析技术博客的HTML |
||||
|
Document doc = Jsoup.connect(url).get(); |
||||
|
Elements titles = doc.select(".post-title"); |
||||
|
for (Element e : titles) { |
||||
|
articles.add(new Article(e.text(), url, "")); |
||||
|
} |
||||
|
} else if (url.contains("news.example.com")) { |
||||
|
// 解析新闻网站的HTML |
||||
|
Document doc = Jsoup.connect(url).get(); |
||||
|
Elements items = doc.select(".article-headline"); |
||||
|
for (Element e : items) { |
||||
|
articles.add(new Article(e.text(), url, "")); |
||||
|
} |
||||
|
} else { |
||||
|
view.printError("Unsupported website!"); |
||||
|
} |
||||
|
} |
||||
|
``` |
||||
|
|
||||
|
**痛点提炼**： |
||||
|
> "看到了吗？每支持一个新网站，就要在这里加一个`else if`。这就是W1我们痛批的'牵一发而动全身'，只不过这次灾难地点从`main`搬到了`CrawlCommand`。" |
||||
|
> |
||||
|
> "更重要的是，我们上节课辛辛苦苦实现了Command模式，难道解析逻辑又要回到if-else地狱吗？**这就是W10要解决的第一个问题：怎么让解析逻辑也可插拔？**" |
||||
|
|
||||
|
**第二个隐患——共享状态的回顾**： |
||||
|
> "还有一件事，我们上节课结束前提到的：`List<Article> articles`在所有Command之间共享。任何一个Command都可以往里面塞东西、删东西、甚至清空。这是W10要解决的第二个问题：**怎么给数据装上'防盗门'？**" |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
### 4.2 策略模式：解析器的“插头标准化”（18分钟） |
||||
|
|
||||
|
#### 4.2.1 从类比切入 |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "先讲个生活场景。你家里墙上有一个三孔插座，你可以插电视、插电脑、插手机充电器——任何符合这个标准的电器都能用。插座不在乎你是什么电器，它只认接口标准。" |
||||
|
|
||||
|
**类比映射**： |
||||
|
|
||||
|
| 生活场景 | 代码对应 | |
||||
|
|----------|----------| |
||||
|
| 三孔插座 | `CrawlStrategy` 接口 | |
||||
|
| 电视/电脑充电器 | 具体解析策略（BlogStrategy/NewsStrategy） | |
||||
|
| 电流 | 输入：URL + Document；输出：List\<Article\> | |
||||
|
| 你（使用者） | CrawlCommand | |
||||
|
| 插座面板 | 解析器工厂 | |
||||
|
|
||||
|
> "策略模式的核心思想就是：**定义一个算法接口，让具体的算法实现可以互相替换，而使用算法的客户端不受影响。**" |
||||
|
|
||||
|
#### 4.2.2 策略模式定义 |
||||
|
|
||||
|
```java |
||||
|
// src/main/java/com/crawler/strategy/CrawlStrategy.java |
||||
|
package com.crawler.strategy; |
||||
|
|
||||
|
import com.crawler.model.Article; |
||||
|
import org.jsoup.nodes.Document; |
||||
|
import java.util.List; |
||||
|
|
||||
|
public interface CrawlStrategy { |
||||
|
/** |
||||
|
* 从已获取的Document中解析文章列表 |
||||
|
* @param url 原始请求URL（用于填充Article） |
||||
|
* @param doc Jsoup解析后的Document |
||||
|
* @return 解析出的文章列表 |
||||
|
*/ |
||||
|
List<Article> parse(String url, Document doc); |
||||
|
|
||||
|
/** |
||||
|
* 判断此策略是否为给定URL服务 |
||||
|
* @param url 待判断的URL |
||||
|
* @return true表示此策略可以处理该URL |
||||
|
*/ |
||||
|
boolean supports(String url); |
||||
|
} |
||||
|
``` |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "注意，策略接口里有两个方法。`parse`是干活的那个，`supports`是'我能不能干这个活'——这是什么？**这是合同！** 任何网站想被我们爬虫支持，就必须签署这份合同：告诉我你是不是我的客户（supports），以及怎么解析你（parse）。" |
||||
|
|
||||
|
#### 4.2.3 具体策略实现示例 |
||||
|
|
||||
|
```java |
||||
|
// BlogStrategy.java - 技术博客解析策略 |
||||
|
public class BlogStrategy implements CrawlStrategy { |
||||
|
@Override |
||||
|
public boolean supports(String url) { |
||||
|
return url.contains("blog.example.com"); |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public List<Article> parse(String url, Document doc) { |
||||
|
List<Article> articles = new ArrayList<>(); |
||||
|
Elements titles = doc.select(".post-title"); |
||||
|
for (Element e : titles) { |
||||
|
articles.add(new Article(e.text(), url, "")); |
||||
|
} |
||||
|
return articles; |
||||
|
} |
||||
|
} |
||||
|
|
||||
|
// NewsStrategy.java - 新闻网站解析策略 |
||||
|
public class NewsStrategy implements CrawlStrategy { |
||||
|
@Override |
||||
|
public boolean supports(String url) { |
||||
|
return url.contains("news.example.com"); |
||||
|
} |
||||
|
|
||||
|
@Override |
||||
|
public List<Article> parse(String url, Document doc) { |
||||
|
List<Article> articles = new ArrayList<>(); |
||||
|
Elements items = doc.select(".article-headline"); |
||||
|
for (Element e : items) { |
||||
|
articles.add(new Article(e.text(), url, "")); |
||||
|
} |
||||
|
return articles; |
||||
|
} |
||||
|
} |
||||
|
``` |
||||
|
|
||||
|
**对比：策略模式 vs 硬编码if-else** |
||||
|
|
||||
|
| 维度 | if-else屎山 | 策略模式 | |
||||
|
|------|-------------|----------| |
||||
|
| 新增网站 | 改CrawlCommand，加else if | 新写一个类，实现CrawlStrategy | |
||||
|
| 修改解析逻辑 | 在CrawlCommand里翻找对应的else if | 只改对应策略类 | |
||||
|
| 测试 | 必须启动整个爬虫 | 单独对Strategy做单元测试 | |
||||
|
| 是否符合开闭原则 | ❌ 对修改开放 | ✅ 对扩展开放，对修改关闭 | |
||||
|
|
||||
|
**与Command模式的对比（加深理解）**： |
||||
|
> "上节课Command模式，我们为每个命令定义一个类；这节课策略模式，我们为每个网站的解析算法定义一个类。**本质上都是同一个OOP思想：用多态替代条件分支。** 只不过Command的接口是`execute()`，Strategy的接口是`parse()`。" |
||||
|
> |
||||
|
> "这张图你们可以记下来：**接口是消除if-else的利器，多态是接口的灵魂。**" |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
### 4.3 解析器工厂：自动匹配的魔法（14分钟） |
||||
|
|
||||
|
#### 4.3.1 问题引出 |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "现在我们有A网站的策略、B网站的策略。问题来了：谁来选策略？谁来遍历所有策略，找到一个supports返回true的？" |
||||
|
> |
||||
|
> "如果把这个逻辑写在CrawlCommand里，那策略模式就白用了——CrawlCommand还是得'知道'有哪些策略。我们要的是一个黑盒子：**把URL丢进去，自动弹出一个合适的解析器。**" |
||||
|
|
||||
|
#### 4.3.2 解析器工厂的实现 |
||||
|
|
||||
|
```java |
||||
|
// src/main/java/com/crawler/strategy/StrategyFactory.java |
||||
|
package com.crawler.strategy; |
||||
|
|
||||
|
import java.util.ArrayList; |
||||
|
import java.util.List; |
||||
|
|
||||
|
public class StrategyFactory { |
||||
|
private final List<CrawlStrategy> strategies = new ArrayList<>(); |
||||
|
|
||||
|
// 注册策略——新的网站只需在这里加一行 |
||||
|
public StrategyFactory() { |
||||
|
strategies.add(new BlogStrategy()); |
||||
|
strategies.add(new NewsStrategy()); |
||||
|
// 未来增加新网站：strategies.add(new XxxStrategy()); |
||||
|
} |
||||
|
|
||||
|
/** |
||||
|
* 根据URL自动匹配解析策略 |
||||
|
* @param url 目标URL |
||||
|
* @return 匹配的策略，如果没有匹配返回null |
||||
|
*/ |
||||
|
public CrawlStrategy getStrategy(String url) { |
||||
|
for (CrawlStrategy s : strategies) { |
||||
|
if (s.supports(url)) { |
||||
|
return s; |
||||
|
} |
||||
|
} |
||||
|
return null; // 未找到匹配策略 |
||||
|
} |
||||
|
} |
||||
|
``` |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "这个工厂类足够简单：一个List存所有策略，一个方法遍历找到匹配的。但简单不等于不强大。** |
||||
|
> |
||||
|
> **关键点**：新增网站支持，只需要——" |
||||
|
1. 写一个`XxxStrategy`实现`CrawlStrategy` |
||||
|
2. 在工厂构造器里加一行`strategies.add(new XxxStrategy())` |
||||
|
> |
||||
|
> "CrawlCommand一行不改。这就是开闭原则的胜利。" |
||||
|
|
||||
|
#### 4.3.3 从简单工厂到更高级的注册机制（拓展思维） |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "有同学可能会问：还要在工厂构造器里加一行，能不能做到完全零改动？当然可以——用反射或者SPI。" |
||||
|
|
||||
|
**演示概念（不要求实现）**： |
||||
|
```java |
||||
|
// 进阶思路：扫描指定包下的所有CrawlStrategy实现类 |
||||
|
// 用反射自动注册，真正做到“新增类即生效” |
||||
|
// 这是Spring框架的核心思想之一 |
||||
|
``` |
||||
|
|
||||
|
> "这个技术我们暂时不要求掌握，但我希望你们知道：你现在写的每一个`new XxxStrategy()`，在未来都可能进化为框架级别的自动装配。**你现在建立的思维习惯，决定了你未来能走多高。**" |
||||
|
|
||||
|
#### 4.3.4 重构后的CrawlCommand |
||||
|
|
||||
|
```java |
||||
|
public class CrawlCommand implements Command { |
||||
|
private ConsoleView view; |
||||
|
private StrategyFactory strategyFactory; |
||||
|
private ArticleRepository repository; // 注意：这里是Repository了！ |
||||
|
|
||||
|
public CrawlCommand(ConsoleView v, StrategyFactory f, ArticleRepository r) { |
||||
|
this.view = v; |
||||
|
this.strategyFactory = f; |
||||
|
this.repository = r; |
||||
|
} |
||||
|
|
||||
|
public String getName() { return "crawl"; } |
||||
|
|
||||
|
public void execute(String[] args, List<Article> articles) { |
||||
|
if (args.length < 2) { |
||||
|
view.printError("Usage: crawl <url>"); |
||||
|
return; |
||||
|
} |
||||
|
String url = args[1]; |
||||
|
|
||||
|
// 1. 工厂自动选策略 |
||||
|
CrawlStrategy strategy = strategyFactory.getStrategy(url); |
||||
|
if (strategy == null) { |
||||
|
view.printError("No strategy found for: " + url); |
||||
|
return; |
||||
|
} |
||||
|
|
||||
|
// 2. 抓取页面 |
||||
|
view.printInfo("Crawling: " + url); |
||||
|
try { |
||||
|
Document doc = Jsoup.connect(url).get(); |
||||
|
List<Article> parsed = strategy.parse(url, doc); |
||||
|
|
||||
|
// 3. 通过仓库存入（而不是直接操作List） |
||||
|
for (Article a : parsed) { |
||||
|
repository.add(a); |
||||
|
} |
||||
|
view.printSuccess("Crawled " + parsed.size() + " articles."); |
||||
|
} catch (IOException e) { |
||||
|
view.printError("Failed to crawl: " + e.getMessage()); |
||||
|
} |
||||
|
} |
||||
|
} |
||||
|
``` |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "注意这个CrawlCommand现在的职责：拿到URL → 交给工厂选策略 → 执行解析 → 交给仓库存储。**它自己在干什么？在调度！** 这就是上节课我们讲的Controller的'调度思维'，现在向Command内部延伸了。" |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
### 4.4 Repository模式：武装数据访问（12分钟） |
||||
|
|
||||
|
#### 4.4.1 问题重提 |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "回到上节课结束时的那个问题：`List<Article>`在所有Command之间共享。任何一个Command都可以做这些事——" |
||||
|
```java |
||||
|
articles.clear(); // 清空所有文章 |
||||
|
articles.add(null); // 塞入null |
||||
|
articles.remove(0); // 随意删除 |
||||
|
``` |
||||
|
|
||||
|
> "如果一个新同事接手开发，他不知道'不要动这个List'的潜规则，写了一个`articles.clear()`，你的`list`命令就突然什么都不显示了。**靠代码约定维护的秩序，早晚会被打破。我们需要实体的'规则'——代码层面的约束。**" |
||||
|
|
||||
|
#### 4.4.2 ArticleRepository的定义 |
||||
|
|
||||
|
```java |
||||
|
// src/main/java/com/crawler/repository/ArticleRepository.java |
||||
|
package com.crawler.repository; |
||||
|
|
||||
|
import com.crawler.model.Article; |
||||
|
import java.util.ArrayList; |
||||
|
import java.util.Collections; |
||||
|
import java.util.List; |
||||
|
|
||||
|
public class ArticleRepository { |
||||
|
private final List<Article> articles = new ArrayList<>(); |
||||
|
|
||||
|
/** |
||||
|
* 添加一篇文章。注意：不接受null，这是代码层面的规则，不是口头约定。 |
||||
|
*/ |
||||
|
public void add(Article article) { |
||||
|
if (article == null) { |
||||
|
throw new IllegalArgumentException("Article cannot be null"); |
||||
|
} |
||||
|
articles.add(article); |
||||
|
} |
||||
|
|
||||
|
/** |
||||
|
* 获取所有文章的只读视图 |
||||
|
* 调用者无法通过此返回值修改内部数据 |
||||
|
*/ |
||||
|
public List<Article> getAll() { |
||||
|
return Collections.unmodifiableList(articles); |
||||
|
} |
||||
|
|
||||
|
/** |
||||
|
* 获取文章数量 |
||||
|
*/ |
||||
|
public int size() { |
||||
|
return articles.size(); |
||||
|
} |
||||
|
|
||||
|
/** |
||||
|
* 清空（仅管理员可调——下一篇：权限控制） |
||||
|
*/ |
||||
|
public void clear() { |
||||
|
articles.clear(); |
||||
|
} |
||||
|
} |
||||
|
``` |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "三个关键设计点——" |
||||
|
> |
||||
|
> - **add()拒绝null**：规则写在代码里，不是写在邮件里 |
||||
|
> - **getAll()返回不可修改的视图**：`Collections.unmodifiableList()`——调用者如果尝试add/remove，会**直接抛异常**，不是'悄悄的bug' |
||||
|
> - **ClearCommand要清空数据？调`repository.clear()`**，而不是直接操作List |
||||
|
> |
||||
|
> "这就是面向对象的第一课——封装。把数据藏起来，只暴露安全的方法。从'直接操作集合'到'通过仓库存取'，是程序员成熟度的分水岭。" |
||||
|
|
||||
|
#### 4.4.3 仓库引入后的架构变化 |
||||
|
|
||||
|
**Command接口的execute方法调整**： |
||||
|
|
||||
|
```java |
||||
|
// 调整前（W9） |
||||
|
public interface Command { |
||||
|
String getName(); |
||||
|
void execute(String[] args, List<Article> articles); |
||||
|
} |
||||
|
|
||||
|
// 调整后（W10） |
||||
|
public interface Command { |
||||
|
String getName(); |
||||
|
void execute(String[] args, ArticleRepository repository); |
||||
|
} |
||||
|
``` |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "这个改动很小——把`List<Article>`换成`ArticleRepository`。但语义完全不同：之前是'给你数据随便玩'，现在是'给你一个安全的存取通道'。" |
||||
|
|
||||
|
**所有Command同步调整**： |
||||
|
|
||||
|
```java |
||||
|
// ListCommand.java - 调整后 |
||||
|
public class ListCommand implements Command { |
||||
|
private ConsoleView view; |
||||
|
public ListCommand(ConsoleView v) { this.view = v; } |
||||
|
public String getName() { return "list"; } |
||||
|
public void execute(String[] args, ArticleRepository repository) { |
||||
|
view.display(repository.getAll()); // 通过仓库获取数据 |
||||
|
} |
||||
|
} |
||||
|
|
||||
|
// ClearCommand.java（新增示例） |
||||
|
public class ClearCommand implements Command { |
||||
|
private ConsoleView view; |
||||
|
public ClearCommand(ConsoleView v) { this.view = v; } |
||||
|
public String getName() { return "clear"; } |
||||
|
public void execute(String[] args, ArticleRepository repository) { |
||||
|
repository.clear(); |
||||
|
view.printSuccess("All articles cleared."); |
||||
|
} |
||||
|
} |
||||
|
``` |
||||
|
|
||||
|
**Controller和main的调整**： |
||||
|
|
||||
|
```java |
||||
|
// App.java - 调整后 |
||||
|
public class App { |
||||
|
public static void main(String[] args) { |
||||
|
ConsoleView view = new ConsoleView(); |
||||
|
ArticleRepository repository = new ArticleRepository(); // 替代 List<Article> |
||||
|
StrategyFactory factory = new StrategyFactory(); // 新增 |
||||
|
|
||||
|
CrawlerController controller = new CrawlerController(view, repository, factory); |
||||
|
|
||||
|
view.printSuccess("Welcome to CLI Crawler v2.0!"); |
||||
|
view.printInfo("Type 'help' for commands."); |
||||
|
|
||||
|
while (true) { |
||||
|
controller.handle(view.readLine()); |
||||
|
} |
||||
|
} |
||||
|
} |
||||
|
``` |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
### 4.5 整体架构串联（8分钟） |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "现在我们把所有部件串起来，看看一个`crawl https://blog.example.com`命令走过的完整路径。" |
||||
|
|
||||
|
**时序图（口述配白板绘制）**： |
||||
|
``` |
||||
|
用户输入 "crawl https://blog.example.com" |
||||
|
│ |
||||
|
▼ |
||||
|
ConsoleView.readLine() |
||||
|
│ |
||||
|
▼ |
||||
|
CrawlerController.handle("crawl https://blog.example.com") |
||||
|
│ Map查找 "crawl" → CrawlCommand |
||||
|
▼ |
||||
|
CrawlCommand.execute(args, repository) |
||||
|
│ |
||||
|
├─► StrategyFactory.getStrategy(url) |
||||
|
│ │ 遍历List<CrawlStrategy> |
||||
|
│ │ BlogStrategy.supports(url) → true! |
||||
|
│ ▼ |
||||
|
│ 返回 BlogStrategy |
||||
|
│ |
||||
|
├─► Jsoup.connect(url).get() → Document |
||||
|
│ |
||||
|
├─► BlogStrategy.parse(url, doc) → List<Article> |
||||
|
│ |
||||
|
└─► for each article: repository.add(article) |
||||
|
│ |
||||
|
▼ |
||||
|
ArticleRepository.articles.add(article) |
||||
|
|
||||
|
最终：ConsoleView.printSuccess("Crawled N articles.") |
||||
|
``` |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "七步调用，每一步职责清晰：View负责输入输出，Controller负责路由，Command负责调度，Factory负责匹配，Strategy负责解析，Repository负责存储。**没有哪个类干了两个人的活，也没有哪个类不知道自己的活是什么。**" |
||||
|
> |
||||
|
> "这就是工程化——不是把代码写得快，是把代码写得对。" |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
### 4.6 代码落地（20分钟） |
||||
|
|
||||
|
**教师准备**：课前准备一份“W9升级到W10”的改动清单，现场演示关键改动。 |
||||
|
|
||||
|
**改动清单**： |
||||
|
1. 新建`strategy/`包，创建`CrawlStrategy`接口 |
||||
|
2. 新建`strategy/BlogStrategy.java` |
||||
|
3. 新建`strategy/NewsStrategy.java` |
||||
|
4. 新建`strategy/StrategyFactory.java` |
||||
|
5. 新建`repository/`包，创建`ArticleRepository.java` |
||||
|
6. 修改`Command`接口的`execute`签名 |
||||
|
7. 修改`CrawlCommand`，引入`StrategyFactory`和`ArticleRepository` |
||||
|
8. 修改其余所有`Command`实现类 |
||||
|
9. 修改`CrawlerController`构造器 |
||||
|
10. 修改`App.java` |
||||
|
|
||||
|
**教师演示关键步骤**（重点演示）： |
||||
|
- `ArticleRepository`的`Collections.unmodifiableList()` |
||||
|
- `StrategyFactory`的遍历匹配逻辑 |
||||
|
- `CrawlCommand`重写后的调度结构 |
||||
|
|
||||
|
**刻意埋入的“找茬点”**： |
||||
|
> "我在`StrategyFactory.getStrategy()`里，如果没有匹配的策略就返回`null`。然后在`CrawlCommand`里检查null。这其实叫'null object pattern的前奏'——如果我不想让Command检查null，我应该怎么改工厂？大家带着这个问题用AI探究。" |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
### 4.7 架构反思与W11预告（5分钟） |
||||
|
|
||||
|
**教师口播**： |
||||
|
> "现在我们的架构比W9强壮多了：解析逻辑可插拔，数据访问有守卫。但还有一些漏洞——" |
||||
|
|
||||
|
**逐一点破**： |
||||
|
1. **异常处理**：`CrawlCommand`用了一个笼统的`catch (IOException e)`，如果解析过程中抛出其他异常怎么办？ |
||||
|
2. **网络超时**：如果目标网站3秒没响应，当前代码会一直等吗？ |
||||
|
3. **日志缺失**：所有的成功/失败信息只输出到终端，如果程序半夜跑，第二天想看昨晚抓了多少——看不了。 |
||||
|
4. **重试机制**：如果一次失败就直接报错，要不要给个重试的机会？ |
||||
|
|
||||
|
**W11预告**： |
||||
|
> "下周，我们会做三件事：**自定义异常体系**、**工程化日志框架**、**防御式编程与重试机制**。W9搭骨架，W10装盔甲，W11要让这个系统**经得起现实的毒打**。" |
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--- |
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### 4.8 实践任务（5分钟） |
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**任务要求**： |
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1. 从W9代码出发，完成W10升级 |
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2. 实现至少两个`CrawlStrategy`（可以是模拟的，不要求真实爬取） |
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3. 实现`StrategyFactory`和`ArticleRepository` |
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4. 确保所有Command通过Repository访问数据 |
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5. 运行并测试完整流程 |
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**验收标准**： |
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- [x] 新增策略类只需新建文件+工厂注册一行，其余代码零改动 |
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- [x] `ArticleRepository`的`getAll()`返回不可修改视图 |
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- [x] `CrawlCommand`不包含任何网站特定的解析逻辑 |
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- [x] `StrategyFactory`能根据URL自动匹配正确的策略 |
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- [x] 所有Command的`execute`方法签名已更新为`ArticleRepository` |
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- [x] 无任何地方直接操作`List<Article>` |
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--- |
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## 五、课后作业 |
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### 5.1 必做任务 |
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1. **完善ArticleRepository**：增加`addAll(List<Article>)`批量添加方法，注意防御null |
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2. **★ AnalyzeCommand（集大成作业）**： |
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- 实现`analyze <url>`命令 |
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- 内部调用`StrategyFactory`匹配策略 |
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- 调用策略解析文章后，**不存到Repository**，而是分析统计信息： |
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- 文章总数 |
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- 标题平均长度 |
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- 按某种规则排名的Top 5 |
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- 结果只输出，不存储 |
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- **提示**：这就是策略的复用——同一个解析策略，既能为`crawl`服务（存入仓库），也能为`analyze`服务（仅分析） |
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|
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3. **AI架构审计**：将完整代码的类图（或类名与方法签名列表）发给AI，指令： |
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> "作为Java架构审计师，请检查：①策略模式的实现是否正确解耦（CrawlCommand是否仍然包含网站特定逻辑）；②Repository是否真正封装了数据访问（是否存在绕过Repository直接操作List的地方）；③工厂的匹配逻辑是否存在性能隐患。请给出具体的改进建议。" |
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|
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### 5.2 选做任务 |
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|
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1. **正则策略匹配**：将`Supports()`的判断从`url.contains()`改为正则表达式，让一张策略可以匹配一类URL |
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|
2. **默认策略（DefaultStrategy）**：当没有策略匹配时，提供一个通用的“标题提取”逻辑 |
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|
3. **策略优先级**：给每个策略加一个`priority`字段，工厂按优先级匹配（而不是按注册顺序） |
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4. **思考并回答（200字）**： |
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> "策略模式中，策略的`supports()`方法有可能让两个策略都返回true，这时该选哪个？`StrategyFactory`的遍历顺序会如何影响结果？你有什么解决方案？" |
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|
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|
### 5.3 思考题 |
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|
|
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|
1. **Repository与List的区别是什么？** 如果Repository只是包了一层List，为什么还要用？ |
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|
2. **策略工厂的演进**：如果网站数量增加到100个，逐个注册的写法还合适吗？你想到什么解决方案？ |
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|
3. **`Collections.unmodifiableList()`返回的是什么？** 它真的“不可修改”吗？如果原List被修改，这个不可修改视图会怎样？ |
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|
|
||||
|
--- |
||||
|
|
||||
|
## 六、AI协同升级 |
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|
|
||||
|
### 架构审计师任务（必做） |
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|
|
||||
|
**学生执行步骤**： |
||||
|
1. 画出当前项目的类依赖图（手绘或工具生成） |
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|
2. 将类名和依赖关系发给AI |
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|
3. 输入指令： |
||||
|
> "作为Java架构审计师，请检查这个爬虫项目的架构。重点关注：①策略模式是否真正实现了开闭原则（增加新网站是否真的只需新增类）；②Repository封装是否完整（是否有绕过Repository的路径）；③是否存在循环依赖。请逐一指出问题并给出改进建议。" |
||||
|
|
||||
|
**预期AI输出**： |
||||
|
- 指出是否还存在“改一处影响多处”的耦合 |
||||
|
- 判断Repository的API设计是否完备 |
||||
|
- 评价整体架构的开闭原则达成度 |
||||
|
|
||||
|
### 进阶AI探究（选做） |
||||
|
|
||||
|
> "假设我有一个CrawlStrategy接口和10个实现类。不用工厂模式，直接用一个Map<String, CrawlStrategy>存起来，key是策略名称。这和StrategyFactory设计有什么本质区别？各自的优缺点是什么？" |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 七、教学反思与调整记录 |
||||
|
|
||||
|
| 日期 | 事项 | 调整内容 | |
||||
|
|------|------|----------| |
||||
|
| 2026-05-01 | 首次编写 | 基于W9骨架，引入策略模式+工厂+Repository | |
||||
|
| 2026-05-07 | 结构优化 | 调整策略模式与工厂的讲解顺序，先策略后工厂更自然 | |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 附录1：W9到W10改动对照表 |
||||
|
|
||||
|
| 改动项 | W9代码 | W10代码 | |
||||
|
|--------|--------|---------| |
||||
|
| 数据存储 | `List<Article> articles` | `ArticleRepository repository` | |
||||
|
| Command接口 | `execute(String[], List<Article>)` | `execute(String[], ArticleRepository)` | |
||||
|
| 解析逻辑位置 | `CrawlCommand`内部 | 各`CrawlStrategy`实现类 | |
||||
|
| URL匹配 | 无（硬编码） | `StrategyFactory.getStrategy(url)` | |
||||
|
| 数据添加 | `articles.add(article)` | `repository.add(article)` | |
||||
|
| 数据读取 | 直接遍历`articles` | `repository.getAll()` | |
||||
|
|
||||
|
## 附录2：常见问题速查 |
||||
|
|
||||
|
| 问题 | 解答 | |
||||
|
|------|------| |
||||
|
| 策略模式和Command模式有什么区别？ | Command封装“动作”（做什么事），Strategy封装“算法”（怎么做）。在爬虫中：crawl是命令（动作），如何解析是策略（算法）。 | |
||||
|
| 工厂一定要叫Factory吗？ | 不必须。但叫Factory意味着“创建对象”的职责，符合模式命名的惯例。 | |
||||
|
| `Collections.unmodifiableList()`有什么用？ | 返回一个只读视图，调用add/remove等方法会抛`UnsupportedOperationException`。 | |
||||
|
| Repository和DAO有什么区别？ | 在我们的上下文中可以视为同义词。严谨地说，Repository是领域驱动设计的概念，更偏向“集合语义”；DAO更偏数据库操作。 | |
||||
|
| 策略的`supports()`返回true但解析失败怎么办？ | 那是策略实现的bug，该策略应修复。Factory不负责验证策略的正确性。 | |
||||
|
|
||||
|
## 附录3：教学逻辑说明 |
||||
|
|
||||
|
| 顺序 | 内容 | 设计理由 | |
||||
|
|------|------|----------| |
||||
|
| 1 | W9回顾+痛点暴露 | 承上启下，从已知问题引出新知识 | |
||||
|
| 2 | 策略模式 | 解决解析逻辑耦合问题，深化多态理解 | |
||||
|
| 3 | 解析器工厂 | 解决策略选择问题，引入工厂模式 | |
||||
|
| 4 | Repository模式 | 解决数据安全问题，实践封装原则 | |
||||
|
| 5 | 架构串联 | 将所有部件统一，形成完整心智模型 | |
||||
|
| 6 | 代码落地 | 实践验证，从“听懂”到“会做” | |
||||
|
| 7 | 架构反思+预告 | 暴露新问题，为W11健壮性工程铺垫 | |
||||
|
|
||||
|
--- |
||||
|
|
||||
|
## 版本说明 |
||||
|
|
||||
|
- **v1（本版）**：基于W9教案模式首次编写，包含策略模式、工厂模式、Repository模式的完整引入 |
||||
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Reference in new issue