1.命令模式的定義及使用場景

定義：

使用場景：

需要支持事務操作。

2. 命令模式的優缺點

2.1優點

2.2缺點

3.注意事項

4. 命令模式的實現方式

public abstract class Command {    //執行具體操作命令    public  abstract void execute();}
public class ConcreteCommand1 extends Command {    PRivate  Receiver receiver;    public ConcreteCommand1() {        this.receiver = new ConcreteReceiver1();    }    public void setReceiver(Receiver receiver) {        this.receiver = receiver;    }    @Override    public void execute() {        if(receiver!=null){            receiver.doSomething();        }    }}
public class ConcreteCommand2 extends Command {    private  Receiver receiver;    public ConcreteCommand2() {        this.receiver = new ConcreteReceiver2();    }    public void setReceiver(Receiver receiver) {        this.receiver = receiver;    }    @Override    public void execute() {        if(receiver!=null){            receiver.doSomething();        }    }}
public abstract  class Receiver {    public abstract void doSomething();}
public class ConcreteReceiver1 extends Receiver {    @Override    public void doSomething() {        System.out.println("ConcreteReceiver1 do...");    }}
public class ConcreteReceiver2 extends Receiver {    @Override    public void doSomething() {        System.out.println("ConcreteReceiver2 do...");    }}
public class Invoker {    private Command command;    public void setCommand(Command command) {        this.command = command;    }    public void action() {        this.command.execute();    }}
public class Test {    public static void main(String args[]) {        Invoker invoker = new Invoker();        Receiver receiver = new ConcreteReceiver1();        Command command = new ConcreteCommand1();        invoker.setCommand(command);        invoker.action();        Receiver receiver2 = new ConcreteReceiver2();        Command command2 = new ConcreteCommand2();        invoker.setCommand(command2);        invoker.action();    }}