8.命令模式

1.将一个请求封装为一个对象，使发出请求的责任和执行请求的责任分割开。这样两者之间通过命令对象进行沟通，这样方便将命令对象进行储存、传递、调用、增加与管理。这样可以将方法的请求者和方法的实现者分离开，实现解耦。而且请求的增减对现有的方法不会产生影响，满足开闭原则。一般命令模式的的实现方式如下：命令-->接受这-->实现者。

2.下面已兵工厂为实例实现简单的命令模式。兵工厂有两个部门，一个生产枪支，一个生产弹药，国防部首先下达生产命令给兵工厂的经理，兵工厂经理接受命令后命令具体的生产部门开动生产线，完成任务。模式如下：国防部下命令（command）--> 兵工厂经理（receiver）--> 生产部门（execute）。

3.实现

(1) 生产部门

package com.java.dp.command;

/**
 * @Author lizhilong
 * @create 2019/12/6 14:12
 * @desc 执行者接口
 */
public abstract class Department {

    public abstract  void create();
}

package com.java.dp.command;

/**
 * @Author lizhilong
 * @create 2019/12/6 14:13
 * @desc 执行者实现
 */
public class GunDepartment extends  Department {
    @Override
    public void create() {
        System.out.println("------------本部门负责制造枪支-----------");
    }
}

package com.java.dp.command;

/**
 * @Author lizhilong
 * @create 2019/12/6 14:14
 * @desc  执行者实现
 */
public class BulletsDepartment extends Department {
    @Override
    public void create() {
        System.out.println("--------------本部门负责制造子弹---------------");
    }
}

（2）命令

package com.java.dp.command;

/**
 * @Author lizhilong
 * @create 2019/12/6 14:10
 * @desc  命令接口
 */
public interface Command {

    void  execute();
}

package com.java.dp.command;

/**
 * @Author lizhilong
 * @create 2019/12/6 14:18
 * @desc 枪支生产命令
 */
public class GunCommand implements Command {
    private GunDepartment gunDepartment;

    public GunCommand(){
        gunDepartment = new GunDepartment();
    }

    @Override
    public void execute() {
        gunDepartment.create();
    }
}

package com.java.dp.command;

/**
 * @Author lizhilong
 * @create 2019/12/6 14:20
 * @desc 子弹生产命令
 */
public class BulletsCommand implements  Command{

    private BulletsDepartment bulletsDepartment;

    public BulletsCommand(){
        bulletsDepartment = new BulletsDepartment();
    }

    @Override
    public void execute() {
        bulletsDepartment.create();
    }
}

（3）接受者

package com.java.dp.command;

/**
 * @Author lizhilong
 * @create 2019/12/6 14:22
 * @desc 命令接受者
 */
public class CommandReceiver {

    private  Command command;

    public CommandReceiver(Command command){
        this.command = command;
    }

    public void  call(){
        this.command.execute();
    }
}

（4）客户端

package com.java.dp.command;

/**
 * @Author lizhilong
 * @create 2019/12/6 14:25
 * @desc
 */
public class CommandClient {

    public static void main(String[] args) {

        System.out.println("----------------国防部下命令生产枪支-------------");
        Command gunCommand = new GunCommand();
        System.out.println("----------------兵工厂经理收到命令---------------");
        CommandReceiver receiver = new CommandReceiver(gunCommand);
        System.out.println("----------------经理下达生产命令---------------");
        receiver.call();

        System.out.println("\n");

        System.out.println("----------------国防部下命令生产弹药-------------");
        Command bulletsCommand = new BulletsCommand();
        System.out.println("----------------兵工厂经理收到命令---------------");
        CommandReceiver receiver2 = new CommandReceiver(bulletsCommand);
        System.out.println("----------------经理下达生产命令---------------");
        receiver2.call();

    }
}