行为型-命令模式

JavaBoy_XJ2025-12-31 22:26

1. 项目结构

bash 复制代码 
	command-pattern-demo/
	├── pom.xml
	├── src/
	│   ├── main/
	│   │   ├── java/
	│   │   │   └── com/
	│   │   │       └── demo/
	│   │   │           └── command/
	│   │   │               ├── Command.java
	│   │   │               ├── Light.java
	│   │   │               ├── LightOnCommand.java
	│   │   │               ├── LightOffCommand.java
	│   │   │               ├── CeilingFan.java
	│   │   │               ├── CeilingFanHighCommand.java
	│   │   │               ├── CeilingFanOffCommand.java
	│   │   │               ├── Stereo.java
	│   │   │               ├── StereoOnWithCDCommand.java
	│   │   │               ├── StereoOffCommand.java
	│   │   │               ├── MacroCommand.java
	│   │   │               ├── RemoteControl.java
	│   │   │               ├── NoCommand.java
	│   │   │               └── Client.java
	│   │   └── resources/
	└── test/

Maven配置文件 (pom.xml)

xml 复制代码 
<?xml version="1.0" encoding="UTF-8"?>
<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 
         http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.demo</groupId>
    <artifactId>command-pattern-demo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.24</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

2. 代码实现

  1. 命令接口 (Command.java)

    java 复制代码 
    package com.demo.command;

/**
 * 命令接口：所有命令都需要实现这个接口
 */
@FunctionalInterface
public interface Command {
    void execute();
    
    // Java 8 支持默认方法，可以添加默认实现
    default void undo() {
        System.out.println("撤销操作未实现");
    }
}

  2. 接收者类 - 电灯 (Light.java)

    java 复制代码 
    package com.demo.command;

import lombok.Getter;

/**
 * 接收者类：知道如何执行具体的操作
 */
@Getter
public class Light {
    private String location;
    private boolean isOn = false;
    
    public Light(String location) {
        this.location = location;
    }
    
    public void on() {
        this.isOn = true;
        System.out.println(location + " 电灯已打开");
    }
    
    public void off() {
        this.isOn = false;
        System.out.println(location + " 电灯已关闭");
    }
}

  3. 具体命令类 - 打开电灯 (LightOnCommand.java)

    java 复制代码 
    package com.demo.command;

/**
 * 具体命令类：实现打开电灯的命令
 */
public class LightOnCommand implements Command {
    private Light light;
    
    public LightOnCommand(Light light) {
        this.light = light;
    }
    
    @Override
    public void execute() {
        light.on();
    }
    
    @Override
    public void undo() {
        light.off();
    }
    
    @Override
    public String toString() {
        return "打开 " + light.getLocation() + " 的电灯";
    }
}

  4. 具体命令类 - 关闭电灯 (LightOffCommand.java)

    java 复制代码 
    package com.demo.command;

/**
 * 具体命令类：实现关闭电灯的命令
 */
public class LightOffCommand implements Command {
    private Light light;
    
    public LightOffCommand(Light light) {
        this.light = light;
    }
    
    @Override
    public void execute() {
        light.off();
    }
    
    @Override
    public void undo() {
        light.on();
    }
    
    @Override
    public String toString() {
        return "关闭 " + light.getLocation() + " 的电灯";
    }
}

  5. 接收者类 - 吊扇 (CeilingFan.java)

    java 复制代码 
    package com.demo.command;

import lombok.Getter;

/**
 * 接收者类：吊扇
 */
@Getter
public class CeilingFan {
    public static final int HIGH = 3;
    public static final int MEDIUM = 2;
    public static final int LOW = 1;
    public static final int OFF = 0;
    
    private String location;
    private int speed;
    
    public CeilingFan(String location) {
        this.location = location;
        this.speed = OFF;
    }
    
    public void high() {
        this.speed = HIGH;
        System.out.println(location + " 吊扇设置为高速");
    }
    
    public void medium() {
        this.speed = MEDIUM;
        System.out.println(location + " 吊扇设置为中速");
    }
    
    public void low() {
        this.speed = LOW;
        System.out.println(location + " 吊扇设置为低速");
    }
    
    public void off() {
        this.speed = OFF;
        System.out.println(location + " 吊扇已关闭");
    }
}

  6. 具体命令类 - 吊扇高速命令 (CeilingFanHighCommand.java)

    java 复制代码 
    package com.demo.command;

/**
 * 具体命令类：设置吊扇为高速
 */
public class CeilingFanHighCommand implements Command {
    private CeilingFan ceilingFan;
    private int previousSpeed;
    
    public CeilingFanHighCommand(CeilingFan ceilingFan) {
        this.ceilingFan = ceilingFan;
    }
    
    @Override
    public void execute() {
        previousSpeed = ceilingFan.getSpeed();
        ceilingFan.high();
    }
    
    @Override
    public void undo() {
        if (previousSpeed == CeilingFan.HIGH) {
            ceilingFan.high();
        } else if (previousSpeed == CeilingFan.MEDIUM) {
            ceilingFan.medium();
        } else if (previousSpeed == CeilingFan.LOW) {
            ceilingFan.low();
        } else {
            ceilingFan.off();
        }
    }
    
    @Override
    public String toString() {
        return "设置 " + ceilingFan.getLocation() + " 的吊扇为高速";
    }
}

  7. 具体命令类 - 关闭吊扇命令 (CeilingFanOffCommand.java)

    java 复制代码 
    package com.demo.command;

/**
 * 具体命令类：关闭吊扇
 */
public class CeilingFanOffCommand implements Command {
    private CeilingFan ceilingFan;
    private int previousSpeed;
    
    public CeilingFanOffCommand(CeilingFan ceilingFan) {
        this.ceilingFan = ceilingFan;
    }
    
    @Override
    public void execute() {
        previousSpeed = ceilingFan.getSpeed();
        ceilingFan.off();
    }
    
    @Override
    public void undo() {
        if (previousSpeed == CeilingFan.HIGH) {
            ceilingFan.high();
        } else if (previousSpeed == CeilingFan.MEDIUM) {
            ceilingFan.medium();
        } else if (previousSpeed == CeilingFan.LOW) {
            ceilingFan.low();
        } else {
            ceilingFan.off();
        }
    }
    
    @Override
    public String toString() {
        return "关闭 " + ceilingFan.getLocation() + " 的吊扇";
    }
}

  8. 接收者类 - 音响 (Stereo.java)

    java 复制代码 
    package com.demo.command;

import lombok.Getter;

/**
 * 接收者类：音响系统
 */
@Getter
public class Stereo {
    private String location;
    private int volume = 5;
    private boolean isOn = false;
    
    public Stereo(String location) {
        this.location = location;
    }
    
    public void on() {
        this.isOn = true;
        System.out.println(location + " 音响已打开");
    }
    
    public void off() {
        this.isOn = false;
        System.out.println(location + " 音响已关闭");
    }
    
    public void setCD() {
        System.out.println(location + " 音响设置为CD模式");
    }
    
    public void setVolume(int volume) {
        this.volume = volume;
        System.out.println(location + " 音响音量设置为: " + volume);
    }
}

  9. 具体命令类 - 打开音响并播放CD (StereoOnWithCDCommand.java)

    java 复制代码 
    package com.demo.command;

/**
 * 具体命令类：打开音响并播放CD
 */
public class StereoOnWithCDCommand implements Command {
    private Stereo stereo;
    
    public StereoOnWithCDCommand(Stereo stereo) {
        this.stereo = stereo;
    }
    
    @Override
    public void execute() {
        stereo.on();
        stereo.setCD();
        stereo.setVolume(11);
    }
    
    @Override
    public void undo() {
        stereo.off();
    }
    
    @Override
    public String toString() {
        return "打开 " + stereo.getLocation() + " 的音响并播放CD";
    }
}

  10. 具体命令类 - 关闭音响 (StereoOffCommand.java)

    java 复制代码 
    package com.demo.command;

/**
 * 具体命令类：关闭音响
 */
public class StereoOffCommand implements Command {
    private Stereo stereo;
    
    public StereoOffCommand(Stereo stereo) {
        this.stereo = stereo;
    }
    
    @Override
    public void execute() {
        stereo.off();
    }
    
    @Override
    public void undo() {
        stereo.on();
        stereo.setCD();
        stereo.setVolume(11);
    }
    
    @Override
    public String toString() {
        return "关闭 " + stereo.getLocation() + " 的音响";
    }
}

  11. 宏命令类 - 一次执行多个命令 (MacroCommand.java)

    java 复制代码 
    package com.demo.command;

import java.util.ArrayList;
import java.util.List;

/**
 * 宏命令：一次执行多个命令
 */
public class MacroCommand implements Command {
    private List<Command> commands;
    
    public MacroCommand(List<Command> commands) {
        this.commands = new ArrayList<>(commands);
    }
    
    @Override
    public void execute() {
        System.out.println("=== 开始执行宏命令 ===");
        commands.forEach(Command::execute);
        System.out.println("=== 宏命令执行完成 ===");
    }
    
    @Override
    public void undo() {
        System.out.println("=== 开始撤销宏命令 ===");
        // 反向执行撤销操作
        for (int i = commands.size() - 1; i >= 0; i--) {
            commands.get(i).undo();
        }
        System.out.println("=== 宏命令撤销完成 ===");
    }
    
    public void addCommand(Command command) {
        commands.add(command);
    }
    
    @Override
    public String toString() {
        return "宏命令，包含 " + commands.size() + " 个子命令";
    }
}

  12. 空命令类 - 默认空实现 (NoCommand.java)

    java 复制代码 
    package com.demo.command;

/**
 * 空命令：用于初始化遥控器按钮，避免空指针检查
 * 这是空对象模式的应用
 */
public class NoCommand implements Command {
    @Override
    public void execute() {
        // 什么都不做
    }
    
    @Override
    public void undo() {
        // 什么都不做
    }
    
    @Override
    public String toString() {
        return "空命令";
    }
}

  13. 调用者类 - 遥控器 (RemoteControl.java)

    java 复制代码 
    package com.demo.command;

import java.util.Stack;

/**
 * 调用者类：遥控器，持有命令对象并触发命令执行
 */
public class RemoteControl {
    private Command[] onCommands;
    private Command[] offCommands;
    private Stack<Command> undoStack;
    
    public RemoteControl() {
        onCommands = new Command[7];
        offCommands = new Command[7];
        undoStack = new Stack<>();
        
        Command noCommand = new NoCommand();
        for (int i = 0; i < 7; i++) {
            onCommands[i] = noCommand;
            offCommands[i] = noCommand;
        }
    }
    
    public void setCommand(int slot, Command onCommand, Command offCommand) {
        if (slot < 0 || slot >= onCommands.length) {
            throw new IllegalArgumentException("无效的插槽: " + slot);
        }
        
        onCommands[slot] = onCommand;
        offCommands[slot] = offCommand;
    }
    
    public void onButtonWasPushed(int slot) {
        if (slot < 0 || slot >= onCommands.length) {
            throw new IllegalArgumentException("无效的插槽: " + slot);
        }
        
        onCommands[slot].execute();
        undoStack.push(onCommands[slot]);
    }
    
    public void offButtonWasPushed(int slot) {
        if (slot < 0 || slot >= offCommands.length) {
            throw new IllegalArgumentException("无效的插槽: " + slot);
        }
        
        offCommands[slot].execute();
        undoStack.push(offCommands[slot]);
    }
    
    public void undoButtonWasPushed() {
        if (!undoStack.isEmpty()) {
            Command lastCommand = undoStack.pop();
            System.out.println("=== 执行撤销操作 ===");
            lastCommand.undo();
        } else {
            System.out.println("没有可撤销的操作");
        }
    }
    
    public void showCommands() {
        System.out.println("\n======= 遥控器配置 =======");
        for (int i = 0; i < onCommands.length; i++) {
            System.out.println("[插槽 " + i + "] " + 
                    onCommands[i] + " / " + offCommands[i]);
        }
        System.out.println("=========================\n");
    }
    
    // 使用Java 8的Lambda表达式创建命令（函数式接口）
    public void setLambdaCommand(int slot, Runnable onAction, Runnable offAction) {
        setCommand(slot, 
                () -> onAction.run(), 
                () -> offAction.run());
    }
}

  14. 客户端类 - 演示使用 (Client.java)

    java 复制代码 
    package com.demo.command;

import java.util.Arrays;

/**
 * 客户端：演示命令模式的使用
 */
public class Client {
    public static void main(String[] args) {
        System.out.println("=== 命令模式演示：智能家居控制系统 ===\n");
        
        // 1. 创建接收者（设备）
        Light livingRoomLight = new Light("客厅");
        Light kitchenLight = new Light("厨房");
        CeilingFan ceilingFan = new CeilingFan("卧室");
        Stereo stereo = new Stereo("客厅");
        
        // 2. 创建具体命令
        Command livingRoomLightOn = new LightOnCommand(livingRoomLight);
        Command livingRoomLightOff = new LightOffCommand(livingRoomLight);
        Command kitchenLightOn = new LightOnCommand(kitchenLight);
        Command kitchenLightOff = new LightOffCommand(kitchenLight);
        Command ceilingFanHigh = new CeilingFanHighCommand(ceilingFan);
        Command ceilingFanOff = new CeilingFanOffCommand(ceilingFan);
        Command stereoOnWithCD = new StereoOnWithCDCommand(stereo);
        Command stereoOff = new StereoOffCommand(stereo);
        
        // 3. 创建调用者（遥控器）
        RemoteControl remoteControl = new RemoteControl();
        
        // 4. 设置遥控器按钮
        remoteControl.setCommand(0, livingRoomLightOn, livingRoomLightOff);
        remoteControl.setCommand(1, kitchenLightOn, kitchenLightOff);
        remoteControl.setCommand(2, ceilingFanHigh, ceilingFanOff);
        remoteControl.setCommand(3, stereoOnWithCD, stereoOff);
        
        // 5. 显示遥控器配置
        remoteControl.showCommands();
        
        // 6. 测试遥控器功能
        System.out.println("=== 测试遥控器功能 ===");
        remoteControl.onButtonWasPushed(0);  // 打开客厅灯
        remoteControl.offButtonWasPushed(0); // 关闭客厅灯
        remoteControl.undoButtonWasPushed(); // 撤销
        
        remoteControl.onButtonWasPushed(1);  // 打开厨房灯
        remoteControl.onButtonWasPushed(2);  // 打开吊扇高速
        remoteControl.onButtonWasPushed(3);  // 打开音响
        
        System.out.println("\n=== 测试撤销功能 ===");
        remoteControl.undoButtonWasPushed(); // 撤销音响
        remoteControl.undoButtonWasPushed(); // 撤销吊扇
        remoteControl.undoButtonWasPushed(); // 撤销厨房灯
        
        // 7. 创建宏命令
        System.out.println("\n=== 测试宏命令 ===");
        Command partyOnMacro = new MacroCommand(
                Arrays.asList(livingRoomLightOn, stereoOnWithCD, ceilingFanHigh)
        );
        Command partyOffMacro = new MacroCommand(
                Arrays.asList(livingRoomLightOff, stereoOff, ceilingFanOff)
        );
        
        remoteControl.setCommand(4, partyOnMacro, partyOffMacro);
        remoteControl.showCommands();
        
        System.out.println("=== 执行派对模式 ===");
        remoteControl.onButtonWasPushed(4);  // 执行宏命令
        System.out.println("\n=== 结束派对模式 ===");
        remoteControl.offButtonWasPushed(4); // 执行关闭宏命令
        remoteControl.undoButtonWasPushed(); // 撤销
        
        // 8. 使用Java 8 Lambda表达式（函数式接口）
        System.out.println("\n=== 使用Lambda表达式 ===");
        Light garageLight = new Light("车库");
        
        // 使用Lambda表达式创建命令
        remoteControl.setLambdaCommand(5, 
                garageLight::on,  // 方法引用
                garageLight::off  // 方法引用
        );
        
        remoteControl.onButtonWasPushed(5);
        remoteControl.offButtonWasPushed(5);
        
        // 9. 演示空命令模式
        System.out.println("\n=== 测试空命令 ===");
        remoteControl.onButtonWasPushed(6);  // 未设置的插槽，使用空命令
        remoteControl.undoButtonWasPushed(); // 没有可撤销的操作
    }
}

  15. 扩展示例：使用命令队列

    java 复制代码 
    package com.demo.command;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;

/**
 * 命令队列：支持异步执行命令
 */
public class CommandQueue {
    private BlockingQueue<Command> queue;
    private volatile boolean running = true;
    
    public CommandQueue() {
        queue = new LinkedBlockingQueue<>();
        startWorker();
    }
    
    private void startWorker() {
        Thread worker = new Thread(() -> {
            while (running) {
                try {
                    Command command = queue.take();
                    System.out.println("[队列执行] 开始执行命令");
                    command.execute();
                    System.out.println("[队列执行] 命令执行完成");
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }
        });
        worker.setDaemon(true);
        worker.start();
    }
    
    public void addCommand(Command command) {
        queue.offer(command);
    }
    
    public void shutdown() {
        running = false;
    }
}

3. 构建和运行

  1. 使用Maven编译项目：

    bash 复制代码 
    mvn clean compile

  2. 运行主程序：

    bash 复制代码 
    mvn exec:java -Dexec.mainClass="com.demo.command.Client"

  3. 直接运行：

    bash 复制代码 
    java -cp target/classes com.demo.command.Client

4. 核心概念

  • 命令模式将"请求"封装成对象，使得可以参数化其他对象，并支持请求排队、记录日志、撤销等操作。

  • 主要角色：

    • Command（命令接口）：定义执行操作的接口

    • ConcreteCommand（具体命令）：实现命令接口，绑定接收者和动作

    • Receiver（接收者）：知道如何执行具体的操作

    • Invoker（调用者）：持有命令对象并触发命令执行

    • Client（客户端）：创建具体命令并设置接收者

  • 优点：

    • 解耦调用者和接收者

    • 支持撤销和重做

    • 支持命令队列和日志

    • 容易扩展新的命令

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