上传文件至 'project/src/main/java/com/example'

project/src/main/java/com/example/Command.java

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+package com.example;
+
+/**
+ * 命令接口 - 命令模式
+ * 课堂知识点：命令模式、接口
+ */
+public interface Command {
+    void execute() throws CrawlerException;
+    void undo();
+    String getDescription();
+}

project/src/main/java/com/example/CommandInvoker.java

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+package com.example;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 命令调用器 - 命令模式
+ * 课堂知识点：命令模式、集合框架
+ */
+public class CommandInvoker {
+    private final List<Command> history = new ArrayList<>();
+    private int currentIndex = -1;
+    
+    public void execute(Command cmd) throws CrawlerException {
+        cmd.execute();
+        if (currentIndex < history.size() - 1) {
+            history.subList(currentIndex + 1, history.size()).clear();
+        }
+        history.add(cmd);
+        currentIndex++;
+    }
+    
+    public void undo() {
+        if (currentIndex < 0) {
+            System.out.println("没有可撤销的命令");
+            return;
+        }
+        history.get(currentIndex).undo();
+        currentIndex--;
+    }
+    
+    public void showHistory() {
+        System.out.println("\n========== 命令历史 ==========");
+        if (history.isEmpty()) {
+            System.out.println("暂无命令历史");
+        } else {
+            for (int i = 0; i < history.size(); i++) {
+                String marker = (i == currentIndex) ? "→" : " ";
+                System.out.printf("%s %2d. %s\n", marker, i + 1, history.get(i).getDescription());
+            }
+        }
+        System.out.println("==============================");
+    }
+}

project/src/main/java/com/example/Crawler.java

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+package com.example;
+
+import java.io.IOException;
+
+/**
+ * 爬虫基类 - 定义爬虫的通用行为和属性
+ * 课堂知识点：继承、抽象类、封装
+ */
+public abstract class Crawler {
+    
+    /**
+     * 请求间隔时间（毫秒）- 避免被网站封禁
+     */
+    protected static final int DELAY_MS = 1000;
+    
+    /**
+     * 爬取状态：是否成功
+     */
+    private boolean success;
+    
+    /**
+     * 爬取的数据数量
+     */
+    private int dataCount;
+    
+    /**
+     * 爬取数据 - 抽象方法，子类必须实现
+     * 课堂知识点：抽象方法
+     */
+    public abstract void crawl();
+    
+    /**
+     * 打印结果 - 抽象方法，子类必须实现
+     */
+    public abstract void printResults();
+    
+    /**
+     * 保存数据到文件 - 抽象方法，子类必须实现
+     */
+    public abstract void saveToFile(String filename) throws IOException;
+    
+    /**
+     * 保存数据到数据库 - 抽象方法，子类必须实现
+     * 课堂知识点：JDBC、数据库持久化
+     */
+    public abstract void saveToDatabase();
+    
+    /**
+     * 检查网络状态
+     * @return 网络是否可用
+     */
+    protected boolean isNetworkAvailable() {
+        return HttpCrawler.isNetworkAvailable();
+    }
+    
+    /**
+     * 添加请求延迟，避免被封禁
+     */
+    protected void delay() {
+        try {
+            Thread.sleep(DELAY_MS);
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
+    }
+    
+    /**
+     * 获取爬取状态
+     * @return 是否成功
+     */
+    public boolean isSuccess() {
+        return success;
+    }
+    
+    /**
+     * 设置爬取状态
+     * @param success 是否成功
+     */
+    protected void setSuccess(boolean success) {
+        this.success = success;
+    }
+    
+    /**
+     * 获取数据数量
+     * @return 数据数量
+     */
+    public int getDataCount() {
+        return dataCount;
+    }
+    
+    /**
+     * 设置数据数量
+     * @param dataCount 数据数量
+     */
+    protected void setDataCount(int dataCount) {
+        this.dataCount = dataCount;
+    }
+    
+    /**
+     * 获取爬虫名称（默认实现，子类可重写）
+     * @return 爬虫名称
+     */
+    public String getCrawlerName() {
+        return this.getClass().getSimpleName();
+    }
+}

project/src/main/java/com/example/CrawlerCommand.java

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+package com.example;
+
+/**
+ * 爬虫命令 - 命令模式实现
+ */
+public class CrawlerCommand implements Command {
+    private final Crawler crawler;
+    private final String filename;
+    private boolean executed;
+    
+    public CrawlerCommand(Crawler crawler, String filename) {
+        this.crawler = crawler;
+        this.filename = filename;
+        this.executed = false;
+    }
+    
+    @Override
+    public void execute() throws CrawlerException {
+        if (executed) {
+            throw new CrawlerException("命令已经执行过");
+        }
+        try {
+            System.out.println("执行: " + getDescription());
+            crawler.crawl();
+            crawler.printResults();
+            crawler.saveToFile(filename);
+            executed = true;
+        } catch (Exception e) {
+            throw new CrawlerException("执行失败: " + e.getMessage(), e);
+        }
+    }
+    
+    @Override
+    public void undo() {
+        if (!executed) {
+            System.out.println("命令未执行，无法撤销");
+            return;
+        }
+        System.out.println("撤销: " + getDescription());
+        executed = false;
+    }
+    
+    @Override
+    public String getDescription() {
+        return crawler.getCrawlerName() + " -> " + filename;
+    }
+}

project/src/main/java/com/example/CrawlerException.java

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+package com.example;
+
+import java.io.IOException;
+
+/**
+ * 爬虫异常基类 - 异常体系
+ * 课堂知识点：自定义异常、异常继承体系
+ */
+public class CrawlerException extends Exception {
+    public CrawlerException(String message) {
+        super(message);
+    }
+    public CrawlerException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}
+
+/**
+ * 网络异常 - 网络连接失败
+ */
+class NetworkException extends CrawlerException {
+    public NetworkException(String message) { super(message); }
+    public NetworkException(String message, Throwable cause) { super(message, cause); }
+}
+
+/**
+ * 数据解析异常 - HTML/JSON解析失败
+ */
+class DataParseException extends CrawlerException {
+    public DataParseException(String message) { super(message); }
+    public DataParseException(String message, Throwable cause) { super(message, cause); }
+}
+
+/**
+ * 文件保存异常 - 文件写入失败
+ */
+class FileSaveException extends CrawlerException {
+    public FileSaveException(String message) { super(message); }
+    public FileSaveException(String message, IOException cause) { super(message, cause); }
+}