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*.jar |
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*.jar |
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*.class |
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*.log |
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# DataCollect 教学项目 — 最小可运行版本 |
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这是一个最小可用的 Java CLI 演示工程,目标:打印帮助信息以验证运行环境。 |
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构建: |
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```bash |
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mvn -q package |
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``` |
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运行(示例): |
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```bash |
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java -jar target/datacollect-cli-0.1.0-jar-with-dependencies.jar --help |
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``` |
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项目结构(最小): |
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- `src/main/java/com/example/datacollect/Main.java` — CLI 入口,打印帮助 |
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- `pom.xml` — Maven 构建配置,生成可执行 jar |
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<project xmlns="http://maven.apache.org/POM/4.0.0" |
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" |
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> |
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<modelVersion>4.0.0</modelVersion> |
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<groupId>com.example</groupId> |
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<artifactId>datacollect-cli</artifactId> |
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<version>0.1.0</version> |
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<properties> |
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<maven.compiler.source>11</maven.compiler.source> |
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<maven.compiler.target>11</maven.compiler.target> |
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</properties> |
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<build> |
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<plugins> |
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<plugin> |
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<groupId>org.apache.maven.plugins</groupId> |
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<artifactId>maven-compiler-plugin</artifactId> |
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<version>3.8.1</version> |
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</plugin> |
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<plugin> |
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<groupId>org.apache.maven.plugins</groupId> |
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<artifactId>maven-assembly-plugin</artifactId> |
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<version>3.3.0</version> |
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<configuration> |
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<archive> |
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<manifest> |
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<mainClass>com.example.datacollect.Main</mainClass> |
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</manifest> |
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</archive> |
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<descriptorRefs> |
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<descriptorRef>jar-with-dependencies</descriptorRef> |
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</descriptorRefs> |
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</configuration> |
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<executions> |
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<execution> |
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<id>make-assembly</id> |
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<phase>package</phase> |
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<goals> |
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<goal>single</goal> |
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</goals> |
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</execution> |
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</executions> |
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</plugin> |
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</plugins> |
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</build> |
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</project> |
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package com.example.datacollect; |
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import com.example.datacollect.controller.CrawlerController; |
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import com.example.datacollect.model.Article; |
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import com.example.datacollect.view.ConsoleView; |
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import java.util.ArrayList; |
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import java.util.List; |
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public class Main { |
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public static void main(String[] args) { |
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ConsoleView view = new ConsoleView(); |
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List<Article> articles = new ArrayList<>(); |
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CrawlerController controller = new CrawlerController(view, articles); |
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view.printSuccess("Welcome to CLI Crawler (w9_1)! Type help for commands."); |
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while (true) { |
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controller.handle(view.readLine()); |
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} |
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} |
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} |
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package com.example.datacollect.command; |
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import com.example.datacollect.model.Article; |
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import java.util.List; |
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public interface Command { |
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String getName(); |
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void execute(String[] args, List<Article> articles); |
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} |
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package com.example.datacollect.command; |
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import com.example.datacollect.model.Article; |
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import com.example.datacollect.view.ConsoleView; |
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import java.util.List; |
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public class CrawlCommand implements Command { |
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private final ConsoleView view; |
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public CrawlCommand(ConsoleView view) { |
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this.view = view; |
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} |
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@Override |
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public String getName() { |
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return "crawl"; |
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} |
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@Override |
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public void execute(String[] args, List<Article> articles) { |
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if (args.length < 2) { |
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view.printError("Usage: crawl <url>"); |
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return; |
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} |
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view.printInfo("Stub: would crawl " + args[1]); |
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} |
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} |
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package com.example.datacollect.command; |
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import com.example.datacollect.model.Article; |
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import com.example.datacollect.view.ConsoleView; |
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import java.util.List; |
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public class ExitCommand implements Command { |
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private final ConsoleView view; |
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public ExitCommand(ConsoleView view) { |
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this.view = view; |
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} |
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@Override |
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public String getName() { |
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return "exit"; |
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} |
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@Override |
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public void execute(String[] args, List<Article> articles) { |
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view.printSuccess("Bye!"); |
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System.exit(0); |
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} |
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} |
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package com.example.datacollect.command; |
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import com.example.datacollect.model.Article; |
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import com.example.datacollect.view.ConsoleView; |
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import java.util.List; |
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public class HelpCommand implements Command { |
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private final ConsoleView view; |
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public HelpCommand(ConsoleView view) { |
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this.view = view; |
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} |
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@Override |
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public String getName() { |
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return "help"; |
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} |
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@Override |
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public void execute(String[] args, List<Article> articles) { |
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view.printInfo("Commands: crawl <url>, list, history, help, exit"); |
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} |
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} |
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package com.example.datacollect.command; |
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import com.example.datacollect.model.Article; |
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import com.example.datacollect.view.ConsoleView; |
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import java.util.List; |
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public class HistoryCommand implements Command { |
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private final ConsoleView view; |
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private final List<String> history; |
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public HistoryCommand(ConsoleView view, List<String> history) { |
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this.view = view; |
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this.history = history; |
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} |
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@Override |
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public String getName() { |
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return "history"; |
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} |
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@Override |
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public void execute(String[] args, List<Article> articles) { |
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if (history.isEmpty()) { |
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view.printInfo("暂无命令历史记录。"); |
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return; |
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} |
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for (int i = 0; i < history.size(); i++) { |
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System.out.println((i + 1) + ". " + history.get(i)); |
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} |
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} |
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} |
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package com.example.datacollect.command; |
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import com.example.datacollect.model.Article; |
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import com.example.datacollect.view.ConsoleView; |
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import java.util.List; |
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public class ListCommand implements Command { |
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private final ConsoleView view; |
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public ListCommand(ConsoleView view) { |
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this.view = view; |
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} |
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@Override |
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public String getName() { |
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return "list"; |
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} |
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@Override |
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public void execute(String[] args, List<Article> articles) { |
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view.display(articles); |
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} |
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} |
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package com.example.datacollect.controller; |
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import com.example.datacollect.command.Command; |
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import com.example.datacollect.command.CrawlCommand; |
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import com.example.datacollect.command.ExitCommand; |
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import com.example.datacollect.command.HelpCommand; |
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import com.example.datacollect.command.HistoryCommand; |
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import com.example.datacollect.command.ListCommand; |
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import com.example.datacollect.model.Article; |
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import com.example.datacollect.view.ConsoleView; |
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import java.util.ArrayList; |
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import java.util.HashMap; |
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import java.util.List; |
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import java.util.Map; |
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public class CrawlerController { |
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private final Map<String, Command> commands = new HashMap<>(); |
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private final ConsoleView view; |
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private final List<Article> articles; |
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private final List<String> history = new ArrayList<>(); |
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public CrawlerController(ConsoleView view, List<Article> articles) { |
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this.view = view; |
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this.articles = articles; |
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register(new HelpCommand(view)); |
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register(new ListCommand(view)); |
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register(new CrawlCommand(view)); |
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register(new ExitCommand(view)); |
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register(new HistoryCommand(view, history)); |
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} |
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private void register(Command command) { |
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commands.put(command.getName(), command); |
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} |
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public void handle(String input) { |
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String text = input == null ? "" : input.trim(); |
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if (text.isEmpty()) { |
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return; |
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} |
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history.add(text); |
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String[] args = text.split("\\s+"); |
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String cmdName = args[0].toLowerCase(); |
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Command command = commands.get(cmdName); |
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if (command == null) { |
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view.printError("Unknown command: " + cmdName); |
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return; |
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} |
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command.execute(args, articles); |
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} |
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} |
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package com.example.datacollect.model; |
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public class Article { |
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private String title; |
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private String url; |
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private String content; |
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private String author; |
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private String publishDate; |
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public Article(String title, String url, String content) { |
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this.title = title; |
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this.url = url; |
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this.content = content; |
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} |
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public Article(String title, String url, String content, String author, String publishDate) { |
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this.title = title; |
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this.url = url; |
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this.content = content; |
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this.author = author; |
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this.publishDate = publishDate; |
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} |
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public String getTitle() { |
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return title; |
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} |
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public void setTitle(String title) { |
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this.title = title; |
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} |
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public String getUrl() { |
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return url; |
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} |
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public void setUrl(String url) { |
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this.url = url; |
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} |
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public String getContent() { |
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return content; |
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} |
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public void setContent(String content) { |
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this.content = content; |
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} |
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public String getAuthor() { |
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return author; |
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} |
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public void setAuthor(String author) { |
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this.author = author; |
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} |
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public String getPublishDate() { |
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return publishDate; |
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} |
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public void setPublishDate(String publishDate) { |
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this.publishDate = publishDate; |
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} |
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@Override |
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public String toString() { |
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return "Article{" |
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+ "title='" + title + '\'' |
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+ ", url='" + url + '\'' |
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+ ", author='" + author + '\'' |
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+ ", publishDate='" + publishDate + '\'' |
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+ '}'; |
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} |
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} |
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package com.example.datacollect.view; |
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import com.example.datacollect.model.Article; |
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import java.util.List; |
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import java.util.Scanner; |
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public class ConsoleView { |
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private static final String ANSI_RESET = "\u001B[0m"; |
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private static final String ANSI_GREEN = "\u001B[32m"; |
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private static final String ANSI_RED = "\u001B[31m"; |
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private static final String ANSI_BLUE = "\u001B[34m"; |
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private final Scanner scanner = new Scanner(System.in); |
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public String readLine() { |
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System.out.print("> "); |
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return scanner.nextLine(); |
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} |
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public void printSuccess(String msg) { |
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System.out.println(ANSI_GREEN + msg + ANSI_RESET); |
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} |
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public void printError(String msg) { |
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System.out.println(ANSI_RED + msg + ANSI_RESET); |
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} |
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public void printInfo(String msg) { |
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System.out.println(ANSI_BLUE + msg + ANSI_RESET); |
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} |
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public void display(List<Article> articles) { |
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if (articles.isEmpty()) { |
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printInfo("暂无文章,请先执行 crawl。"); |
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return; |
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} |
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for (int i = 0; i < articles.size(); i++) { |
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Article a = articles.get(i); |
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System.out.println((i + 1) + ". " + a.getTitle() + " | " + a.getUrl()); |
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} |
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} |
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} |
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--- |
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# 教案:《高级程序设计》第9周——工程架构:从"写代码"到"造系统" |
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| 项目 | 内容 | |
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|------|------| |
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| **课程名称** | 高级程序设计 | |
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| **周次** | 第9周 | |
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| **主题** | 工程架构——从"写代码"到"造系统" | |
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| **学时** | 2学时(90分钟) | |
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| **授课对象** | 具备Python基础、已完成Java面向对象特性学习的学生 | |
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| **教学环境** | JDK 17+、IntelliJ IDEA、Maven(模板) | |
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| **前情提要** | 本课程原计划使用JavaFX GUI,后根据教学反馈转向CLI + MVC + 爬虫工程化 | |
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|
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--- |
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## 教学调整说明:为什么选择CLI而不是GUI? |
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> **原计划**:JavaFX桌面应用 → **新计划**:CLI命令行应用 |
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| 维度 | GUI (JavaFX) | CLI (命令行) | |
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|------|--------------|-------------| |
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| **学习重心** | 布局、控件、事件监听 | 架构、分层、命令路由 | |
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| **学生痛点** | "窗口点击"与后端能力无关 | 真正锻炼工程思维 | |
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| **AI辅助** | AI生成FXML,学生看不懂 | AI辅助重构架构 | |
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| **工程化** | 脱离真实后端开发场景 | 模拟真实服务器/大数据开发 | |
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| **核心转型** | "视觉装饰"优先 | "逻辑架构"优先 | |
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**决策理由**: |
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1. **985学生需要的是工程思维**,不是拖控件 |
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2. **接口抽象**是弱项,CLI + MVC更能暴露这个问题 |
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3. **彩色终端**足够酷炫,且代码量可控 |
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**更深层的教育价值**: |
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> 在GUI框架中,架构已被框架强制划定,学生只是"遵守规矩";而CLI世界里没有任何框架告诉你模型在哪、视图在哪——**当外部约束消失,内部的工程纪律才真正建立**。这正是本节课要传递的核心精神。 |
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|
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--- |
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|
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## 一、教学目标 |
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| 目标维度 | 具体描述 | |
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|----------|----------| |
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| **知识掌握** | 理解MVC架构的职责划分及其演化脉络;掌握Maven项目结构与pom.xml基础;理解Command模式的路由原理。 | |
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| **工程实践** | 能搭建规范的Maven项目包结构;能实现基于Scanner的控制台交互;能用Command接口实现可扩展的命令路由;能识别架构中的"越权行为"。 | |
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| **思维转型** | 从"一个类写全部"转向"分层解耦";从"修改现有代码"转向"新增类实现功能";从"满足功能"转向"代码的工程洁癖"。 | |
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| **工具应用** | 利用AI辅助审查MVC职责越权;让AI扮演"架构审计师"检查分层是否清晰;理解AI生成代码中的架构缺陷。 | |
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--- |
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|
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## 二、教学重点与难点 |
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| 项目 | 内容 | 突破方法 | |
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|------|------|----------| |
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| **重点** | MVC三层职责划分、CLI交互实现、Command接口解耦、代码中的工程细节(常量、输出归属) | 以"新增命令需要改什么"为切入点,展示Command模式的优势;通过现场"代码找茬"强化细节意识 | |
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| **难点** | Controller不写业务逻辑、Command接口的多态实现、共享数据模型的设计缺陷识别 | 现场演示:增加一个命令只需新建类,无需修改Controller;暴露`List<Article>`共享引用的问题并预告解决方案 | |
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|
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--- |
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|
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## 三、教学过程设计(90分钟) |
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| 环节 | 时间 | 教学内容 | 师生活动 | AI协同点 | |
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|------|------|----------|----------|----------| |
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| **1. 痛点引入:从脚本到工程的鸿沟** | 10' | 展示"意大利面"式爬虫代码,演示改一处需要动全身 | **教师演示**:现场展示一段混乱代码,让学生找问题 | 用AI分析代码耦合度 | |
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| **2. CLI vs GUI:架构选择的思考** | 10' | 对比两种方案的优缺点,解释为什么CLI更适合培养工程思维 | **教师讲解**:用对比表格说明选择CLI的理由 | — | |
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| **3. MVC分层设计** | 20' | 讲解Model/View/Controller三层职责,用"餐厅类比"强化理解,随后批判类比局限性 | **教师讲解**:配合架构图讲解三层交互,引导学生寻找类比破绽 | 用AI生成MVC职责对照表 | |
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| **4. Command模式:可扩展的命令路由** | 15' | 引入Command接口,解释"一个命令就是一个类" | **类比**:Command像酒店的服务部门,Controller是前台 | 让AI解释Command模式的多态原理 | |
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| **5. Maven模板与环境** | 5' | 直接使用提供的Maven模板,讲解目录结构 | **教师演示**:解压模板 → IDEA打开 → 运行 | — | |
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| **6. 三层代码落地** | 20' | **Model**:Article实体<br>**View**:ConsoleView(ANSI常量)<br>**Command接口**+实现<br>**Controller**:Map路由 | **教师演示**:分步写出代码,刻意埋入1~2个"越权细节"让学生找茬 | 学生用AI做"架构审计" | |
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| **7. 架构反思与展望** | 5' | 指出当前`List<Article>`共享引用的问题,预告W10策略模式与仓库层 | **师生互动**:你发现这个设计有什么风险? | 让AI分析共享可变状态的危害 | |
|||
| **8. 实践任务:空壳程序** | 5' | 搭建完整包结构,实现CLI循环 | 学生现场编码,教师巡视 | 完成后用AI检查包结构 | |
|||
| **9. 总结与过渡** | 5' | 本周实现了"骨架+命令可扩展",下周填入"灵魂"——解析器,并解决数据安全问题 | 总结Command模式优势,预告策略模式 | — | |
|||
|
|||
--- |
|||
|
|||
## 四、核心教学内容脚本 |
|||
|
|||
### 4.1 痛点引入:从脚本到工程的鸿沟(10分钟) |
|||
|
|||
**教师口播**: |
|||
> "同学们,前8周我们学的是Java语法,从变量到类,从继承到接口。但有一个问题:代码写完之后,怎么组织?" |
|||
> |
|||
> "来看这段代码——这是某个同学写的'爬虫',他一个人完成了一个'完整'的项目。" |
|||
|
|||
**展示"脚本式"代码**: |
|||
```java |
|||
public class Crawler { |
|||
public static void main(String[] args) { |
|||
System.out.print("请输入URL: "); |
|||
Scanner scanner = new Scanner(System.in); |
|||
String url = scanner.nextLine(); |
|||
|
|||
List titles = new ArrayList(); |
|||
try { |
|||
Document doc = Jsoup.connect(url).get(); |
|||
Elements elements = doc.select(".post-title"); |
|||
for (Element e : elements) { |
|||
String title = e.text(); |
|||
System.out.println("标题: " + title); |
|||
titles.add(title); |
|||
} |
|||
} catch (Exception ex) { |
|||
System.out.println("出错啦: " + ex.getMessage()); |
|||
} |
|||
} |
|||
} |
|||
``` |
|||
|
|||
**提问引导**: |
|||
1. "如果我想把标题保存到文件,要改哪里?" |
|||
2. "如果我想支持另一个网站,它的HTML结构不一样,要怎么办?" |
|||
3. "如果我想让输出变成彩色,要改哪里?" |
|||
|
|||
**痛点提炼**: |
|||
> "看到了吗?才60行代码,已经'牵一发而动全身'了。这就是一个'脚本'的宿命——功能全混在一起,改一个小需求,整个文件都要翻。" |
|||
> |
|||
> "这周我们要解决:**怎么让代码'改起来不疼'?**" |
|||
|
|||
--- |
|||
|
|||
### 4.2 CLI vs GUI:架构选择的思考(10分钟) |
|||
|
|||
**教师口播**: |
|||
> "既然要写一个'完整'的爬虫应用,我们有两个选择:图形界面(GUI)或命令行界面(CLI)。为什么我推荐CLI而不是GUI?" |
|||
|
|||
**对比表格** |
|||
|
|||
| 维度 | GUI (JavaFX) | CLI (命令行) | |
|||
|------|--------------|-------------| |
|||
| **代码量** | FXML + Controller + CSS,大量模板代码 | 纯Java,代码量可控 | |
|||
| **学习重心** | 布局、控件、事件监听 | 架构、分层、命令路由 | |
|||
| **后端能力** | 几乎无关 | 模拟真实服务器开发 | |
|||
| **可测试性** | 难(需要UI测试框架) | 易(直接测试Command类) | |
|||
| **工程思维** | 弱(关注视觉) | 强(关注逻辑) | |
|||
|
|||
**核心观点**: |
|||
> **CLI更需要MVC!** GUI有现成的事件系统(点击按钮→触发事件),而CLI只有字符流。**没有架构,分分钟写成脚本**。MVC在CLI里是"刚需",不是"装饰"。 |
|||
> |
|||
> **更深一层**:在GUI里,框架已经硬塞给你一套架构,你只是在填空;但在CLI里,所有结构都必须由你亲手搭建。**当外部约束消失,内部的工程纪律才真正开始建立**——这才是本节课的真正目的。 |
|||
|
|||
**CLI也能很酷**: |
|||
- ANSI彩色输出(红/绿/黄/蓝) |
|||
- 表格展示数据 |
|||
- 进度条动画 |
|||
- 模拟真实大数据开发场景 |
|||
|
|||
--- |
|||
|
|||
### 4.3 MVC分层设计(20分钟) |
|||
|
|||
#### 4.3.1 MVC的起源与演进 |
|||
|
|||
**教师口播**: |
|||
> "MVC不是新东西,它是1970年代为桌面应用设计的架构思想。但它的核心——'职责分离'——在任何软件里都适用。" |
|||
|
|||
| 年代 | 场景 | MVC的角色 | |
|||
|------|------|----------| |
|||
| 1970s | Smalltalk-72 GUI | 最早的用户界面架构 | |
|||
| 1990s | Web开发 (Struts) | 后端模板引擎 | |
|||
| 2000s | ASP.NET MVC | 现代Web框架 | |
|||
| 2020s | CLI + API | 解耦业务逻辑与表现层 | |
|||
|
|||
#### 4.3.2 从GUI到CLI的映射 |
|||
|
|||
| GUI组件 | CLI对应 | 说明 | |
|||
|--------|--------|------| |
|||
| 窗口/按钮 | 命令行输入 | **View = 用户交互** | |
|||
| 数据模型 | Article实体类 | **Model = 数据结构** | |
|||
| 事件监听 | Command路由 | **Controller = 调度** | |
|||
|
|||
#### 4.3.3 MVC三层职责 |
|||
|
|||
**架构图示**: |
|||
|
|||
``` |
|||
┌─────────────────────────────────────────┐ |
|||
│ 入口 │ |
|||
│ (main方法) │ |
|||
└─────────────────┬───────────────────────┘ |
|||
│ |
|||
▼ |
|||
┌─────────────────────────────────────────┐ |
|||
│ Controller │ |
|||
│ - 接收命令(crawl, help, exit) │ |
|||
│ - 分发给对应的Command │ |
|||
│ 【口诀】:Controller不管"怎么做", │ |
|||
│ 只管"派给谁" │ |
|||
└─────────┬───────────────┬───────────────┘ |
|||
│ │ |
|||
▼ ▼ |
|||
┌─────────────────┐ ┌─────────────────┐ |
|||
│ Model │ │ View │ |
|||
│ - 数据实体 │ │ - 输入解析 │ |
|||
│ - 业务逻辑 │ │ - 输出格式化 │ |
|||
│ 【口诀】: │ │ 【口诀】: │ |
|||
│ Model管"数据" │ │ View管"呈现" │ |
|||
└─────────────────┘ └─────────────────┘ |
|||
``` |
|||
|
|||
**三层职责详解** |
|||
|
|||
| 层级 | 职责 | 典型代码 | 禁止做什么 | |
|||
|------|------|----------|------------| |
|||
| **Model** | 数据结构 + 业务逻辑 | `class Article { String title; String content; }` | 不能有`System.out.println`,不能有`Scanner` | |
|||
| **View** | 接收用户输入 + 格式化输出 | `class ConsoleView { String readInput(); void print(String); }` | 不能写爬虫逻辑,只做"传声筒" | |
|||
| **Controller** | 协调调度 | `class CrawlerController { void handle(String cmd) { ... } }` | 不能直接写业务细节,委托给Command | |
|||
|
|||
#### 4.3.4 类比强化:"餐厅类比" |
|||
|
|||
> "把MVC想象成一家餐厅: |
|||
> - **Model是后厨**:只管做菜(数据加工),不管谁来吃、怎么端 |
|||
> - **View是服务员**:只管端菜和收钱(输入输出),不管菜怎么做 |
|||
> - **Controller是前台**:只管把顾客的点单传给后厨,把做好的菜端给顾客 |
|||
> |
|||
> 如果后厨开始管'谁来吃饭',这餐厅就乱了。" |
|||
|
|||
#### 4.3.5 对"餐厅类比"的批判性思考(关键!) |
|||
|
|||
**教师导引**: |
|||
> "刚才的类比好理解吗?很好。但任何一个类比都有它的边界,如果把它当成真理,就会出问题。现在我们来给这个类比'找茬'。" |
|||
|
|||
**提问学生**: |
|||
1. "后厨真的完全不知道客人是谁吗?如果客人有忌口(比如不吃香菜),这个信息需不需要传到后厨?" |
|||
2. "服务员只是端菜吗?在真实餐厅里,服务员经常向后厨反馈'客人觉得今天的菜咸了',这属于View→Model的反向影响吗?" |
|||
3. "在这个类比里,我们把前台(Controller)和后厨(Model)的关系说成单向的。但实际上,后厨做完了菜,需要通知前台'菜好了',这不就是**观察者模式**吗?" |
|||
|
|||
**点明本质**: |
|||
> "实际MVC的数据流向常常是**双向**的:Controller调用Model的方法改变数据,Model变化后又通知View更新显示。只不过在本次CLI项目中,我们暂时使用'请求-响应'的单向简化模型——用户输入命令,系统处理,然后立即输出结果。这个简化版够用,但你要知道完整的MVC是更动态的。随着系统复杂,Model层需要一个专门的'仓库类'来管理数据,并通知视图刷新——这正是W10我们将要深入的内容。" |
|||
|
|||
#### 4.3.6 MVC的数据流向(本课程简化版) |
|||
|
|||
``` |
|||
CLI用户输入 |
|||
↓ |
|||
View(解析命令字符串) |
|||
↓ |
|||
Controller(找到对应Command) |
|||
↓ |
|||
Command.execute()(执行业务逻辑) |
|||
↓ |
|||
Model(Article数据,目前暂存于List) |
|||
↓ |
|||
View(display()展示数据) |
|||
↓ |
|||
CLI终端显示 |
|||
``` |
|||
|
|||
--- |
|||
|
|||
### 4.4 Command模式:可扩展的命令路由(15分钟) |
|||
|
|||
**教师口播**: |
|||
> "现在引入一个设计模式——Command(命令)模式。它的核心思想是:**一个命令就是一个类**。" |
|||
|
|||
#### 4.4.1 为什么需要Command模式? |
|||
|
|||
**演示:增加一个命令的代价(switch-case版)** |
|||
```java |
|||
// 现状代码 |
|||
switch (cmd) { |
|||
case "crawl": handleCrawl(); break; |
|||
case "help": showHelp(); break; |
|||
// 如果要增加 list 命令? |
|||
// 1. 加 case "list" |
|||
// 2. 加 handleList() 方法 |
|||
// 3. 可能还要改其他地方... |
|||
} |
|||
``` |
|||
|
|||
**提问**: |
|||
- "如果我想增加10个命令,这个类要改多少次?" |
|||
- "如果我不小心删了一个case,整个程序还能跑吗?" |
|||
|
|||
**痛点提炼**: |
|||
> "每加一个功能,就要在这个类里戳一个洞。**这就是'肥控制器'陷阱**——所有的逻辑都堆在Controller里,它变成了新的'意大利面'。" |
|||
|
|||
#### 4.4.2 Command模式的四个要素 |
|||
|
|||
| 要素 | 角色 | 示例 | |
|||
|------|------|------| |
|||
| **Command接口** | 抽象的"订单" | `Command` 接口 | |
|||
| **ConcreteCommand** | 具体的订单 | `HelpCommand`、`CrawlCommand` | |
|||
| **Invoker** | 接单的前台 | `CrawlerController` | |
|||
| **Receiver** | 执行者 | `ConsoleView`、`ArticleRepository` | |
|||
|
|||
#### 4.4.3 Command接口定义 |
|||
|
|||
```java |
|||
// src/main/java/com/crawler/command/Command.java |
|||
package com.crawler.command; |
|||
|
|||
import com.crawler.model.Article; |
|||
import java.util.List; |
|||
|
|||
public interface Command { |
|||
String getName(); // 命令名,如 "crawl" |
|||
void execute(String[] args, List<Article> articles); // 执行逻辑 |
|||
} |
|||
``` |
|||
|
|||
#### 4.4.4 Controller的变革(从switch到Map) |
|||
|
|||
```java |
|||
// 修改后的Controller |
|||
public class CrawlerController { |
|||
private Map<String, Command> commands; // 用Map存命令 |
|||
private ConsoleView view; // 持有View以输出错误 |
|||
|
|||
public CrawlerController(ConsoleView view, List<Article> articles) { |
|||
this.view = view; |
|||
this.commands = new HashMap<>(); |
|||
// 增加命令无需改Controller代码,只需在这里注册 |
|||
commands.put("crawl", new CrawlCommand(view)); |
|||
commands.put("help", new HelpCommand(view)); |
|||
commands.put("list", new ListCommand(view)); |
|||
commands.put("exit", new ExitCommand(view)); |
|||
} |
|||
|
|||
public void handle(String input) { |
|||
if (input.isEmpty()) return; |
|||
String[] parts = input.split("\\s+"); |
|||
String cmd = parts[0].toLowerCase(); |
|||
|
|||
Command command = commands.get(cmd); |
|||
if (command == null) { |
|||
view.printError("Unknown command: " + cmd); // 通过View输出,而非直接System.out |
|||
return; |
|||
} |
|||
|
|||
// 执行命令,传入参数和文章列表 |
|||
command.execute(parts, articles); |
|||
} |
|||
} |
|||
``` |
|||
|
|||
**对比表格** |
|||
|
|||
| 维度 | switch-case | Command模式 | |
|||
|------|-------------|-------------| |
|||
| 增加命令 | 要改Controller | 新建一个类 | |
|||
| 多态体验 | 无 | execute()的多态调用 | |
|||
| 可测试性 | 难 | 每个Command可单独测试 | |
|||
| 代码量 | 少 | 多,但更清晰 | |
|||
|
|||
**类比强化**: |
|||
> "Command模式就像**酒店的客房服务**:每个服务(清理、送餐、按摩)都是一个独立的部门。前台(Controller)只负责接电话,然后把请求'派发'给对应的部门。部门自己知道怎么干活,不需要前台教。" |
|||
> |
|||
> "如果想新增一个服务,前台只需要'登记'一下,不需要把现有部门重新装修。" |
|||
|
|||
--- |
|||
|
|||
### 4.5 Maven模板与环境(5分钟) |
|||
|
|||
**教师口播**: |
|||
> "这周我们不发愁pom.xml配置。我已经把 Maven 模板准备好了,你们只需要解压、打开、运行。" |
|||
|
|||
**模板使用流程**: |
|||
``` |
|||
1. 解压 [my-crawler-template.zip] |
|||
2. 用 IDEA 打开文件夹 |
|||
3. 右键 pom.xml → Maven → Reload Project |
|||
4. 运行 App.java |
|||
``` |
|||
|
|||
**标准目录结构**: |
|||
``` |
|||
src/main/java/com/crawler/ |
|||
├── model/ |
|||
│ └── Article.java |
|||
├── view/ |
|||
│ └── ConsoleView.java |
|||
├── command/ |
|||
│ ├── Command.java (接口) |
|||
│ ├── CrawlCommand.java |
|||
│ ├── HelpCommand.java |
|||
│ ├── ListCommand.java |
|||
│ └── ExitCommand.java |
|||
└── controller/ |
|||
└── CrawlerController.java |
|||
``` |
|||
|
|||
--- |
|||
|
|||
### 4.6 代码落地(20分钟) |
|||
|
|||
#### 4.6.1 Model层:Article实体 |
|||
|
|||
```java |
|||
// src/main/java/com/crawler/model/Article.java |
|||
package com.crawler.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 + "'}"; |
|||
} |
|||
} |
|||
``` |
|||
|
|||
#### 4.6.2 View层:ANSI常量集中管理(工程细节!) |
|||
|
|||
```java |
|||
// src/main/java/com/crawler/view/ConsoleView.java |
|||
package com.crawler.view; |
|||
|
|||
import com.crawler.model.Article; |
|||
import java.util.List; |
|||
import java.util.Scanner; |
|||
|
|||
public class ConsoleView { |
|||
// ANSI颜色常量——集中管理,避免散落各处 |
|||
private static final String ANSI_GREEN = "\033[32m"; |
|||
private static final String ANSI_RED = "\033[31m"; |
|||
private static final String ANSI_CYAN = "\033[36m"; |
|||
private static final String ANSI_RESET = "\033[0m"; |
|||
|
|||
private Scanner scanner = new Scanner(System.in); |
|||
|
|||
public String readLine() { |
|||
System.out.print("crawler> "); |
|||
return scanner.nextLine().trim(); |
|||
} |
|||
|
|||
public void print(String msg) { |
|||
System.out.println(msg); |
|||
} |
|||
|
|||
public void printSuccess(String msg) { |
|||
print(ANSI_GREEN + msg + ANSI_RESET); |
|||
} |
|||
|
|||
public void printError(String msg) { |
|||
print(ANSI_RED + msg + ANSI_RESET); |
|||
} |
|||
|
|||
public void printInfo(String msg) { |
|||
print(ANSI_CYAN + msg + ANSI_RESET); |
|||
} |
|||
|
|||
// 展示文章列表 |
|||
public void display(List<Article> articles) { |
|||
if (articles.isEmpty()) { |
|||
printInfo("No articles yet. Use 'crawl <url>' first."); |
|||
return; |
|||
} |
|||
print("+----------+--------------------------------+"); |
|||
print("| Title | URL |"); |
|||
print("+----------+--------------------------------+"); |
|||
for (Article a : articles) { |
|||
String title = a.getTitle(); |
|||
if (title.length() > 10) title = title.substring(0, 10) + ".."; |
|||
String url = a.getUrl(); |
|||
if (url.length() > 30) url = url.substring(0, 27) + "..."; |
|||
print("| " + String.format("%-10s", title) + " | " + url + " |"); |
|||
} |
|||
print("+----------+--------------------------------+"); |
|||
printInfo("Total: " + articles.size() + " articles"); |
|||
} |
|||
} |
|||
``` |
|||
|
|||
**教师提示**: |
|||
> "注意:所有ANSI转义码都被定义为`private static final`常量。如果把`\033[32m`散落在项目各处,一旦想调整颜色,就得满世界去改——这正是我们之前痛批的'意大利面'。**这就是工程细节**。" |
|||
|
|||
#### 4.6.3 Command接口与四个实现(全部通过View输出) |
|||
|
|||
```java |
|||
// Command.java |
|||
public interface Command { |
|||
String getName(); |
|||
void execute(String[] args, List<Article> articles); |
|||
} |
|||
|
|||
// HelpCommand.java |
|||
public class HelpCommand implements Command { |
|||
private ConsoleView view; |
|||
public HelpCommand(ConsoleView v) { this.view = v; } |
|||
public String getName() { return "help"; } |
|||
public void execute(String[] args, List<Article> articles) { |
|||
view.printInfo("Commands: crawl <url>, list, help, exit"); |
|||
} |
|||
} |
|||
|
|||
// ListCommand.java |
|||
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, List<Article> articles) { |
|||
view.display(articles); |
|||
} |
|||
} |
|||
|
|||
// CrawlCommand.java (存根) |
|||
public class CrawlCommand implements Command { |
|||
private ConsoleView view; |
|||
public CrawlCommand(ConsoleView v) { this.view = v; } |
|||
public String getName() { return "crawl"; } |
|||
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]); |
|||
} |
|||
} |
|||
|
|||
// ExitCommand.java |
|||
public class ExitCommand implements Command { |
|||
private ConsoleView view; |
|||
public ExitCommand(ConsoleView v) { this.view = v; } |
|||
public String getName() { return "exit"; } |
|||
public void execute(String[] args, List<Article> articles) { |
|||
view.printSuccess("Bye!"); // 全部输出都通过View,绝不让System.out直接出现在这里 |
|||
System.exit(0); |
|||
} |
|||
} |
|||
``` |
|||
|
|||
**故意埋设的"找茬点"**: |
|||
> "我在刚才的代码里有没有隐藏违反MVC原则的地方?`CrawlCommand`的存根里,`view.printInfo("Stub: Would crawl " + args[1]);` —— 这个字符串拼接算是"业务逻辑"吗?留给大家用AI架构审计时讨论。 |
|||
|
|||
#### 4.6.4 Controller:Map路由(全部通过View输出) |
|||
|
|||
```java |
|||
// src/main/java/com/crawler/controller/CrawlerController.java |
|||
package com.crawler.controller; |
|||
|
|||
import com.crawler.command.*; |
|||
import com.crawler.model.Article; |
|||
import com.crawler.view.ConsoleView; |
|||
import java.util.HashMap; |
|||
import java.util.List; |
|||
import java.util.Map; |
|||
|
|||
public class CrawlerController { |
|||
private Map<String, Command> commands = new HashMap<>(); |
|||
private ConsoleView view; // 持有View |
|||
private List<Article> articles; |
|||
|
|||
public CrawlerController(ConsoleView view, List<Article> articles) { |
|||
this.view = view; |
|||
this.articles = articles; |
|||
commands.put("help", new HelpCommand(view)); |
|||
commands.put("list", new ListCommand(view)); |
|||
commands.put("crawl", new CrawlCommand(view)); |
|||
commands.put("exit", new ExitCommand(view)); |
|||
} |
|||
|
|||
public void handle(String input) { |
|||
if (input.isEmpty()) return; |
|||
String[] parts = input.split("\\s+"); |
|||
String cmdName = parts[0].toLowerCase(); |
|||
|
|||
Command cmd = commands.get(cmdName); |
|||
if (cmd == null) { |
|||
view.printError("Unknown command: " + cmdName); // 错误信息也走View! |
|||
return; |
|||
} |
|||
cmd.execute(parts, articles); |
|||
} |
|||
} |
|||
``` |
|||
|
|||
#### 4.6.5 main方法:组装 |
|||
|
|||
```java |
|||
// src/main/java/com/crawler/App.java |
|||
package com.crawler; |
|||
|
|||
import com.crawler.controller.CrawlerController; |
|||
import com.crawler.model.Article; |
|||
import com.crawler.view.ConsoleView; |
|||
import java.util.ArrayList; |
|||
import java.util.List; |
|||
|
|||
public class App { |
|||
public static void main(String[] args) { |
|||
ConsoleView view = new ConsoleView(); |
|||
List<Article> articles = new ArrayList<>(); |
|||
CrawlerController controller = new CrawlerController(view, articles); |
|||
|
|||
view.printSuccess("Welcome to CLI Crawler!"); |
|||
view.printInfo("Type 'help' for commands."); |
|||
|
|||
while (true) { |
|||
controller.handle(view.readLine()); |
|||
} |
|||
} |
|||
} |
|||
``` |
|||
|
|||
#### 4.6.6 架构反思与展望:共享List<Article>的隐患(关键!) |
|||
|
|||
**教师口播**: |
|||
> "现在这个架构已经可用了。但请大家审视一下:我们所有的Command都直接拿到了`List<Article>`的引用。换句话说,任何一个命令都可以随意增、删、改这个列表。" |
|||
> |
|||
> "这就好像一家酒店,所有服务员、厨师、清洁工都能随意进出保险箱——**数据结构完全裸奔了**。" |
|||
|
|||
**提问**: |
|||
- "如果CrawlCommand不小心写错了代码,把一个null塞进articles,HelpCommand会不会受影响?" |
|||
- "如果未来我们要在添加文章时也写入日志文件,现在的设计能优雅实现吗?还是得在所有Command里分别加日志代码?" |
|||
|
|||
**预告解决方案**: |
|||
> "下周,我们将引入**策略模式**和一个真正的**Model仓库层(ArticleRepository)**。这个仓库会把`List`封装起来,对外只提供`add()`、`getAll()`等安全接口。任何命令想修改数据,都必须通过仓库。这就是从'数据结构'到'模型层'的进化——我们W9先搭骨架,W10给它装上盔甲。" |
|||
|
|||
--- |
|||
|
|||
### 4.7 实践任务(5分钟) |
|||
|
|||
**任务要求**: |
|||
1. 使用Maven模板创建项目 |
|||
2. 实现完整包结构(model/view/command/controller) |
|||
3. 实现4个Command:help/list/crawl/exit |
|||
4. `list`命令能展示已抓取的文章 |
|||
5. 运行并测试循环 |
|||
6. **代码找茬(额外加分)**:找出你自己代码中是否存在`System.out`直接调用、硬编码ANSI字符串等"越权行为" |
|||
|
|||
**验收标准**: |
|||
- [x] Maven编译通过 |
|||
- [x] Command接口和4个实现分离在不同文件 |
|||
- [x] Controller里没有switch-case |
|||
- [x] 新增命令只需新建类,不改Controller |
|||
- [x] list命令能正确显示空列表 |
|||
- [x] 所有输出均通过ConsoleView完成,无直接System.out.println(main除外) |
|||
- [x] ANSI颜色码集中定义为View常量 |
|||
|
|||
--- |
|||
|
|||
## 五、课后作业 |
|||
|
|||
### 5.1 必做任务 |
|||
|
|||
1. **完善Article**:增加`author`、`publishDate`字段 |
|||
2. **★ HistoryCommand(强制作业)**: |
|||
- 实现`history`命令,记录用户输入过的所有命令 |
|||
- 使用`List<String>`存储历史(复习W8集合) |
|||
- 示例输出: |
|||
``` |
|||
crawler> history |
|||
1. help |
|||
2. list |
|||
3. crawl https://example.com |
|||
``` |
|||
3. **AI架构审计**:将类名和方法名发给AI,指令: |
|||
> "作为Java架构审计师,请检查我的MVC三层划分是否存在越权行为?Model层是否包含输入输出代码?View层是否越权写了业务逻辑?有没有地方直接使用了System.out或硬编码ANSI码?" |
|||
|
|||
### 5.2 选做任务 |
|||
|
|||
1. **命令别名**:给`crawl`增加别名`c`,`help`增加别名`h` |
|||
2. **URL验证**:检查URL格式是否以http://或https://开头 |
|||
3. **暗色主题**:实现不同的配色方案(利用View中的ANSI常量,只需修改一处即可) |
|||
4. **思考并回答**:分析`List<Article>`共享引用的潜在风险,写一段200字的小结 |
|||
|
|||
### 5.3 思考题 |
|||
|
|||
1. **Command vs switch-case**:增加10个命令,哪种方式代码改动量更小? |
|||
2. **如果不用Command接口,直接用Map存命令类行不行?** 接口的意义是什么? |
|||
3. **Controller里的`commands.put()`能否减少?** 提示:思考"注册机制" |
|||
4. **为什么ExitCommand里的`view.printSuccess("Bye!")`比直接`System.out.println`更"MVC"?** 提示:回忆View的职责 |
|||
|
|||
--- |
|||
|
|||
## 六、AI协同升级 |
|||
|
|||
### 架构审计师任务(必做) |
|||
|
|||
**学生执行步骤**: |
|||
1. 列出项目中所有类名(不含方法实现) |
|||
2. 将类名列表发给AI |
|||
3. 输入指令: |
|||
> "作为Java架构审计师,请检查我的MVC三层划分是否清晰。Model层是否包含了不应该有的代码(Scanner/System.out)?View层是否越权写了业务逻辑?请指出任何一处直接使用System.out.println的地方,并建议如何改正。" |
|||
|
|||
**预期AI输出**: |
|||
- 指出哪一层有越权行为 |
|||
- 建议如何整改 |
|||
- 评价整体架构健康度 |
|||
|
|||
### 进阶AI探究(选做) |
|||
|
|||
> "假设我的Command接口中execute方法接收了一个`List<Article>`参数,请分析这种设计在工程上有什么隐患,并给出重构建议。" |
|||
|
|||
--- |
|||
|
|||
## 七、教学反思与调整记录 |
|||
|
|||
| 日期 | 事项 | 调整内容 | |
|||
|------|------|----------| |
|||
| 2026-04-28 | 首次编写 | 基于CLI+MVC重构 | |
|||
| 2026-04-30 | 教授反馈 | 引入Command模式、提供Maven模板、升级AI协同比 | |
|||
| 2026-04-30 | 逻辑重排 | 按"问题→选择→架构→模式"顺序重写 | |
|||
| 2026-05-01 | v2 vs V3合并 | 融合深度改进:增加教育哲学、批判性思考、ANSI常量、共享List隐患、故意埋坑 | |
|||
|
|||
--- |
|||
|
|||
## 附录1:Maven模板说明 |
|||
|
|||
> 老师提供`my-crawler-template.zip`压缩包,包含: |
|||
> - pom.xml(含Jsoup依赖) |
|||
> - 空的src/main/java结构 |
|||
> - .gitignore |
|||
|
|||
## 附录2:常见问题速查 |
|||
|
|||
| 问题 | 解答 | |
|||
|------|------| |
|||
| IDEA不识别pom.xml | 右键 pom.xml → Maven → Reload Project | |
|||
| 中文乱码 | Settings → Editor → File Encodings → UTF-8 | |
|||
| 包名大小写 | 包名全小写,类名首字母大写 | |
|||
| Command找不到 | 检查是否 implements Command,是否 @Override getName() | |
|||
| 命令不生效 | 检查 commands.put() 是否注册了该命令 | |
|||
| 输出颜色乱码 | IDEA控制台需支持ANSI,Windows下建议使用Windows Terminal或调整设置 | |
|||
| 我的System.out为什么被老师说越权 | View层才是与用户交互的唯一出口,所有输出都应通过View,这样将来改成GUI或日志时只需改View | |
|||
|
|||
## 附录3:教学逻辑说明 |
|||
|
|||
| 顺序 | 内容 | 设计理由 | |
|||
|------|------|----------| |
|||
| 1 | 痛点引入 | 从问题出发,让学生感受"为什么需要架构" | |
|||
| 2 | CLI vs GUI | 解释技术选型,建立"工程思维 > 视觉装饰"的认知 | |
|||
| 3 | MVC分层 | 核心架构概念,理解职责分离,通过类比及批判加深理解 | |
|||
| 4 | Command模式 | 具体实现方式,解决"肥控制器"问题 | |
|||
| 5 | Maven | 工具链支持 | |
|||
| 6 | 代码落地 | 实践验证,刻意植入细节规范,训练工程洁癖 | |
|||
| 7 | 架构反思 | 暴露共享可变状态隐患,为W10策略模式+仓库层做铺垫 | |
|||
| 8 | 实践任务 | 现场编码验证 | |
|||
| 9 | 总结 | 强化认知,预告下周 | |
|||
|
|||
--- |
|||
|
|||
## 版本说明 |
|||
|
|||
- **v1**:首次编写,CLI+MVC基础框架 |
|||
- **v2**:按"问题→选择→架构→模式"逻辑重排 |
|||
- **v3 (本版)**:融合v2结构 + V3深度改进,包含: |
|||
- 更深的CLI教育哲学 |
|||
- 餐厅类比批判性思考 |
|||
- ANSI常量集中管理工程细节 |
|||
- 全部输出走View |
|||
- 共享List架构隐患反思 |
|||
- 故意埋坑让学生找茬 |
|||
- W10铺垫(策略模式+仓库层) |
|||
@ -0,0 +1,5 @@ |
|||
#Generated by Maven |
|||
#Thu Apr 30 11:50:54 CST 2026 |
|||
artifactId=datacollect-cli |
|||
groupId=com.example |
|||
version=0.1.0 |
|||
@ -0,0 +1,530 @@ |
|||
## 高级程序设计 · 第9周 |
|||
|
|||
#### 工程架构:从"写代码"到"造系统" |
|||
|
|||
##### CLI + MVC + Command模式实战 |
|||
|
|||
--- |
|||
|
|||
### 📌 本周导航 |
|||
|
|||
- 痛点引入:脚本的宿命 |
|||
- CLI vs GUI:为什么选命令行? |
|||
- MVC分层:职责分离的艺术 |
|||
- Command模式:可扩展的路由 |
|||
- Maven模板:工程化第一步 |
|||
- 代码落地:从接口到实现 |
|||
- 架构反思:共享数据的隐患 |
|||
- 实践任务 + 课后作业 |
|||
|
|||
--- |
|||
|
|||
### 1️⃣ 痛点引入:从脚本到工程的鸿沟 |
|||
|
|||
#### 这是一段“意大利面”爬虫 |
|||
|
|||
```java |
|||
public class Crawler { |
|||
public static void main(String[] args) { |
|||
System.out.print("请输入URL: "); |
|||
Scanner scanner = new Scanner(System.in); |
|||
String url = scanner.nextLine(); |
|||
List titles = new ArrayList(); |
|||
try { |
|||
Document doc = Jsoup.connect(url).get(); |
|||
Elements elements = doc.select(".post-title"); |
|||
for (Element e : elements) { |
|||
String title = e.text(); |
|||
System.out.println("标题: " + title); |
|||
titles.add(title); |
|||
} |
|||
} catch (Exception ex) { |
|||
System.out.println("出错啦: " + ex.getMessage()); |
|||
} |
|||
} |
|||
} |
|||
``` |
|||
|
|||
--- |
|||
|
|||
### 脚本的三大痛点 |
|||
|
|||
| 需求 | 需要改哪里? | |
|||
|------|--------------| |
|||
| 保存标题到文件 | 改 main 内部逻辑 | |
|||
| 支持不同网站结构 | 全部重写解析代码 | |
|||
| 彩色输出 | 一个一个改 print | |
|||
|
|||
> 😫 **牵一发而动全身 → 改起来疼** |
|||
|
|||
### 本周目标:**让代码“改起来不疼”** |
|||
|
|||
--- |
|||
|
|||
## 2️⃣ CLI vs GUI:架构选择的思考 |
|||
|
|||
### 图形界面 vs 命令行 |
|||
|
|||
| 维度 | GUI (JavaFX) | CLI (命令行) | |
|||
|------|--------------|-------------| |
|||
| 学习重心 | 布局、控件、事件 | **架构、分层、路由** | |
|||
| 后端能力 | 弱 | 模拟真实服务器 | |
|||
| 工程思维 | 弱(关注视觉) | **强(关注逻辑)** | |
|||
| 可测试性 | 难 | 易 | |
|||
|
|||
--- |
|||
|
|||
## 核心观点 |
|||
|
|||
> **CLI 更需要 MVC!** |
|||
|
|||
- GUI 有现成事件系统,框架强塞给你一套架构 |
|||
- CLI 只有字符流 → **没有架构,分分钟写成脚本** |
|||
|
|||
> 🎯 **当外部约束消失,内部的工程纪律才真正开始建立** |
|||
|
|||
### CLI 也能很酷 |
|||
|
|||
- ANSI 彩色输出 |
|||
- 表格展示数据 |
|||
- 模拟大数据/后端开发 |
|||
|
|||
--- |
|||
|
|||
## 3️⃣ MVC 分层设计 |
|||
|
|||
### MVC 的起源与演进 |
|||
|
|||
| 年代 | 场景 | MVC的角色 | |
|||
|------|------|----------| |
|||
| 1970s | Smalltalk-72 GUI | 最早的用户界面架构 | |
|||
| 1990s | Web开发 (Struts) | 后端模板引擎 | |
|||
| 2000s | ASP.NET MVC | 现代Web框架 | |
|||
| 2020s | CLI + API | 解耦业务逻辑与表现层 | |
|||
|
|||
**核心不变:职责分离** |
|||
|
|||
--- |
|||
|
|||
## MVC 三层职责 |
|||
|
|||
![[mvc.png]] |
|||
``` |
|||
┌─────────────────────────────────────────┐ |
|||
│ 入口 │ |
|||
│ (main方法) │ |
|||
└─────────────────┬───────────────────────┘ |
|||
▼ |
|||
┌─────────────────────────────────────────┐ |
|||
│ Controller │ |
|||
│ 只管"派给谁",不管"怎么做" │ |
|||
└─────────┬───────────────┬───────────────┘ |
|||
▼ ▼ |
|||
┌─────────────────┐ ┌─────────────────┐ |
|||
│ Model │ │ View │ |
|||
│ 管"数据" │ │ 管"呈现" │ |
|||
│ + 业务逻辑 │ │ + 输入输出 │ |
|||
└─────────────────┘ └─────────────────┘ |
|||
``` |
|||
|
|||
--- |
|||
|
|||
## 三层“禁止做什么” |
|||
|
|||
| 层级 | 禁止行为 | |
|||
| -------------- | -------------------------------------- | |
|||
| **Model** | 不能有 `System.out.println`,不能有 `Scanner` | |
|||
| **View** | 不能写爬虫逻辑,只做“传声筒” | |
|||
| **Controller** | 不能直接写业务细节,委托给 Command | |
|||
|
|||
> 🔴 **越权就是架构腐败的开始** |
|||
|
|||
--- |
|||
|
|||
## 🍽️ 餐厅类比(帮助理解) |
|||
|
|||
- **Model = 后厨**:只管做菜,不管谁来吃、怎么端 |
|||
- **View = 服务员**:只管端菜和收钱,不管菜怎么做 |
|||
- **Controller = 前台**:接单 → 派给后厨 → 叫服务员上菜 |
|||
|
|||
--- |
|||
|
|||
## 🤔 对类比的批判性思考(关键!) |
|||
|
|||
> 任何类比都有边界,不要当成真理 |
|||
|
|||
| 场景 | 暴露的问题 | |
|||
|------|------------| |
|||
| 客人有忌口(不吃香菜) | 信息需要传到后厨 → Model 可能需要知道 meta 信息 | |
|||
| 服务员反馈“今天的菜咸了” | View → Model 反向影响 | |
|||
| 后厨做完菜通知前台 | **观察者模式**,数据流可能是双向的 | |
|||
|
|||
**本课程简化模型**:请求-响应,单向流 |
|||
|
|||
--- |
|||
|
|||
## MVC 数据流向(本课程简化版) |
|||
|
|||
``` |
|||
CLI用户输入 |
|||
↓ |
|||
View(解析命令字符串) |
|||
↓ |
|||
Controller(找到对应Command) |
|||
↓ |
|||
Command.execute()(执行业务逻辑) |
|||
↓ |
|||
Model(Article数据,暂存于List) |
|||
↓ |
|||
View(display()展示数据) |
|||
↓ |
|||
CLI终端显示 |
|||
``` |
|||
|
|||
--- |
|||
|
|||
## 4️⃣ Command 模式:可扩展的命令路由 |
|||
|
|||
### 为什么需要 Command 模式? |
|||
|
|||
```java |
|||
switch (cmd) { |
|||
case "crawl": handleCrawl(); break; |
|||
case "help": showHelp(); break; |
|||
// 如果要增加 list 命令? |
|||
// 1. 加 case "list" |
|||
// 2. 加 handleList() 方法 |
|||
// 3. 可能还要改其他地方... |
|||
} |
|||
``` |
|||
|
|||
> 每加一个功能,就要在这个类里戳一个洞 → **肥控制器陷阱** |
|||
|
|||
--- |
|||
|
|||
## Command 模式的四个要素 |
|||
|
|||
| 要素 | 角色 | 示例 | |
|||
|------|------|------| |
|||
| Command接口 | 抽象的“订单” | `Command` | |
|||
| ConcreteCommand | 具体的订单 | `HelpCommand` | |
|||
| Invoker | 接单的前台 | `CrawlerController` | |
|||
| Receiver | 执行者 | `ConsoleView`、`ArticleRepository` | |
|||
|
|||
--- |
|||
|
|||
## Command 接口定义 |
|||
|
|||
```java |
|||
package com.crawler.command; |
|||
|
|||
import com.crawler.model.Article; |
|||
import java.util.List; |
|||
|
|||
public interface Command { |
|||
String getName(); |
|||
void execute(String[] args, List<Article> articles); |
|||
} |
|||
``` |
|||
|
|||
--- |
|||
|
|||
## Controller 的变革:从 switch 到 Map |
|||
|
|||
```java |
|||
public class CrawlerController { |
|||
private Map<String, Command> commands = new HashMap<>(); |
|||
|
|||
public CrawlerController(ConsoleView view, List<Article> articles) { |
|||
commands.put("help", new HelpCommand(view)); |
|||
commands.put("list", new ListCommand(view)); |
|||
commands.put("crawl", new CrawlCommand(view)); |
|||
commands.put("exit", new ExitCommand(view)); |
|||
} |
|||
|
|||
public void handle(String input) { |
|||
// 解析命令 → 从 Map 取 Command → 调用 execute |
|||
} |
|||
} |
|||
``` |
|||
|
|||
> **增加新命令:只需新建类,Controller 零改动!** |
|||
|
|||
--- |
|||
|
|||
## 对比:switch-case vs Command |
|||
|
|||
| 维度 | switch-case | Command模式 | |
|||
|------|-------------|-------------| |
|||
| 增加命令 | 要改 Controller | 新建一个类 | |
|||
| 多态体验 | 无 | `execute()` 多态 | |
|||
| 可测试性 | 难 | 每个 Command 单独测试 | |
|||
| 代码量 | 少 | 多,但更清晰 | |
|||
|
|||
> 🏨 **类比:酒店客房服务,前台只负责派单** |
|||
|
|||
--- |
|||
|
|||
## 5️⃣ Maven 模板与环境(5分钟) |
|||
|
|||
### 直接使用模板,不折腾配置 |
|||
|
|||
``` |
|||
my-crawler-template.zip |
|||
↓ 解压 + IDEA打开 |
|||
↓ 右键 pom.xml → Maven → Reload Project |
|||
↓ 运行 App.java |
|||
``` |
|||
|
|||
### 标准目录结构 |
|||
|
|||
``` |
|||
src/main/java/com/crawler/ |
|||
├── model/Article.java |
|||
├── view/ConsoleView.java |
|||
├── command/ |
|||
│ ├── Command.java |
|||
│ ├── CrawlCommand.java |
|||
│ ├── HelpCommand.java |
|||
│ ├── ListCommand.java |
|||
│ └── ExitCommand.java |
|||
└── controller/CrawlerController.java |
|||
``` |
|||
|
|||
--- |
|||
|
|||
## 6️⃣ 代码落地(分步实现) |
|||
|
|||
### Model:Article 实体 |
|||
|
|||
```java |
|||
public class Article { |
|||
private String title; |
|||
private String url; |
|||
private String content; |
|||
// 构造器、getter/setter、toString |
|||
} |
|||
``` |
|||
|
|||
> 📦 只存放数据,没有任何输入输出代码 |
|||
|
|||
--- |
|||
|
|||
## View:ConsoleView(ANSI常量集中管理) |
|||
|
|||
```java |
|||
public class ConsoleView { |
|||
private static final String ANSI_GREEN = "\033[32m"; |
|||
private static final String ANSI_RED = "\033[31m"; |
|||
// ... 其他常量 |
|||
|
|||
public void printSuccess(String msg) { |
|||
System.out.println(ANSI_GREEN + msg + ANSI_RESET); |
|||
} |
|||
public void printError(String msg) { ... } |
|||
public void display(List<Article> articles) { ... } |
|||
} |
|||
``` |
|||
|
|||
> ✨ **所有颜色码集中定义 → 改主题只需改一处** |
|||
|
|||
--- |
|||
|
|||
## Command 实现示例(HelpCommand) |
|||
|
|||
```java |
|||
public class HelpCommand implements Command { |
|||
private ConsoleView view; |
|||
public HelpCommand(ConsoleView v) { this.view = v; } |
|||
public String getName() { return "help"; } |
|||
public void execute(String[] args, List<Article> articles) { |
|||
view.printInfo("Commands: crawl <url>, list, help, exit"); |
|||
} |
|||
} |
|||
``` |
|||
|
|||
> ⚠️ 全部输出通过 `view`,绝不让 `System.out` 直接出现在这里 |
|||
|
|||
--- |
|||
|
|||
## CrawlCommand(存根,下周填坑) |
|||
|
|||
```java |
|||
public class CrawlCommand implements Command { |
|||
private ConsoleView view; |
|||
public CrawlCommand(ConsoleView v) { this.view = v; } |
|||
public String getName() { return "crawl"; } |
|||
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]); |
|||
} |
|||
} |
|||
``` |
|||
|
|||
> 🔍 **找茬点**:这里拼接字符串算是“业务逻辑”吗?留给大家用 AI 审计。 |
|||
|
|||
--- |
|||
|
|||
## ExitCommand |
|||
|
|||
```java |
|||
public class ExitCommand implements Command { |
|||
private ConsoleView view; |
|||
public ExitCommand(ConsoleView v) { this.view = v; } |
|||
public String getName() { return "exit"; } |
|||
public void execute(String[] args, List<Article> articles) { |
|||
view.printSuccess("Bye!"); |
|||
System.exit(0); |
|||
} |
|||
} |
|||
``` |
|||
|
|||
> ✅ 所有输出都通过 View → 将来改 GUI 只需换 View 实现 |
|||
|
|||
--- |
|||
|
|||
## Controller + main 组装 |
|||
|
|||
```java |
|||
// Controller 中持有 Map<String,Command> |
|||
// App.java 中: |
|||
ConsoleView view = new ConsoleView(); |
|||
List<Article> articles = new ArrayList<>(); |
|||
CrawlerController controller = new CrawlerController(view, articles); |
|||
view.printSuccess("Welcome to CLI Crawler!"); |
|||
while (true) { |
|||
controller.handle(view.readLine()); |
|||
} |
|||
``` |
|||
|
|||
> 🔁 完成交互循环 |
|||
|
|||
--- |
|||
|
|||
## 7️⃣ 架构反思:共享 List<Article> 的隐患 |
|||
|
|||
### 当前问题 |
|||
|
|||
- 所有 Command 都直接拿到 `List<Article>` 引用 |
|||
- 任何一个命令都可以随意增、删、改列表 |
|||
- 数据完全“裸奔” |
|||
|
|||
> 🚨 就像酒店所有员工都能进保险箱 |
|||
|
|||
--- |
|||
|
|||
## 提问 |
|||
|
|||
- 如果 `CrawlCommand` 不小心把 `null` 塞进列表,`ListCommand` 会怎样? |
|||
- 如果我们要在添加文章时写日志,现在的设计能优雅实现吗? |
|||
|
|||
### 预告解决方案(W10) |
|||
|
|||
- **策略模式** + **仓库层(ArticleRepository)** |
|||
- 封装 `List`,对外只暴露 `add()`、`getAll()` 等安全接口 |
|||
|
|||
> W9 搭骨架,W10 装上盔甲 |
|||
|
|||
--- |
|||
|
|||
## 8️⃣ 实践任务(现场5分钟) |
|||
|
|||
### 必做项 |
|||
|
|||
1. 使用 Maven 模板创建项目 |
|||
2. 实现完整包结构(model/view/command/controller) |
|||
3. 实现 4 个 Command:help / list / crawl / exit |
|||
4. `list` 能展示已抓取的文章(目前存根即可) |
|||
5. 运行并测试循环 |
|||
|
|||
### 额外加分:代码找茬 |
|||
|
|||
- 检查是否仍有 `System.out` 直接调用 |
|||
- 检查 ANSI 码是否硬编码在多个地方 |
|||
|
|||
--- |
|||
|
|||
## 验收标准 |
|||
|
|||
- [x] Maven 编译通过 |
|||
- [x] Command 接口和 4 个实现在不同文件 |
|||
- [x] Controller 里没有 switch-case |
|||
- [x] 新增命令只需新建类,不改 Controller |
|||
- [x] list 能正确显示空列表 |
|||
- [x] 所有输出均通过 `ConsoleView` |
|||
- [x] ANSI 颜色码集中定义为常量 |
|||
|
|||
--- |
|||
|
|||
## 9️⃣ 课后作业 |
|||
|
|||
### 必做 |
|||
|
|||
1. **完善 Article**:增加 `author`、`publishDate` 字段 |
|||
2. **★ HistoryCommand**:记录用户输入过的所有命令(用 `List<String>`) |
|||
3. **AI 架构审计**:将类名发给 AI,指令: |
|||
> “作为Java架构审计师,请检查我的MVC三层划分是否存在越权行为?” |
|||
|
|||
### 选做 |
|||
|
|||
- 命令别名(c 代替 crawl) |
|||
- URL 格式验证 |
|||
- 暗色主题(修改一处常量) |
|||
- 思考题:分析 `List<Article>` 共享引用的风险(200字小结) |
|||
|
|||
--- |
|||
|
|||
## 🤖 AI 协同升级 |
|||
|
|||
### 架构审计师任务(必做) |
|||
|
|||
**步骤**: |
|||
1. 列出所有类名(不含方法实现) |
|||
2. 发给 AI |
|||
3. 指令:“检查 MVC 分层是否清晰,是否有越权行为” |
|||
|
|||
### 进阶探究(选做) |
|||
|
|||
> “假设我的 Command 接口中 execute 方法接收了一个 `List<Article>` 参数,请分析这种设计在工程上有什么隐患,并给出重构建议。” |
|||
|
|||
--- |
|||
|
|||
## 📚 总结与过渡 |
|||
|
|||
### 本周成果 |
|||
|
|||
- ✅ 工程化包结构 |
|||
- ✅ MVC 分层清晰 |
|||
- ✅ Command 模式实现可扩展路由 |
|||
- ✅ 所有输出走 View,常量集中管理 |
|||
|
|||
### 下周预告 |
|||
|
|||
- **策略模式**:封装爬取算法 |
|||
- **仓库层(Repository)**:武装 `List<Article>`,解决共享隐患 |
|||
|
|||
> 🚀 从“写代码”到“造系统”,踏出坚实第一步! |
|||
|
|||
--- |
|||
|
|||
## Q&A |
|||
|
|||
### 常见问题 |
|||
|
|||
| 问题 | 解答 | |
|||
|------|------| |
|||
| IDEA 不识别 pom.xml | 右键 → Maven → Reload Project | |
|||
| 中文乱码 | Settings → File Encodings → UTF-8 | |
|||
| 输出颜色乱码 | Windows 建议使用 Windows Terminal | |
|||
| 我的 System.out 被批评 | View 才是唯一输出出口 | |
|||
|
|||
--- |
|||
|
|||
## 谢谢! |
|||
|
|||
### 课件已上传,模板在课程群 |
|||
|
|||
**保持工程洁癖,下周见!** |
|||
|
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Reference in new issue