Java设计模式之--策略模式(strategy)

行为型模式：

 行为型模式，共11种：策略模式、模板方法模式、观察者模式、迭代子模式、责任链模式、命令模式、备忘录模式、状态模式、访问者模式、中介者模式、解释器模式。根据它们的具体技术实现可分为4类，第一类：通过父类与子类的关系进行实现。第二类：两个类之间。第三类：类的状态。第四类：通过中间类如下图：

策略模式(strategy)

概念：

定义一系列的算法,把每一个算法单独实现并封装, 并且使它们可相互替换。使得算法可独立于使用它的客户而变化。客户可以决定采用哪种策略（算法）

案例：

Message 选择通过Email 还是短讯发送信息给特定联系人

来看类图：

联系人 类

public class PhoneContract {
    private String email;
    private String phone;
    private String name;

    public String getEmail() {
        return email;
    }

    public PhoneContract setEmail(String email) {
        this.email = email;
        return this;
    }

    public String getName() {
        return name;
    }

    public PhoneContract setName(String name) {
        this.name = name;
        return this;
    }

    public String getPhone() {
        return phone;
    }

    public PhoneContract setPhone(String phone) {
        this.phone = phone;
        return this;
    }
}      

MessageSendor接口      
   

public interface MessageSendor {
    public void send(PhoneContract phoneContract,String message);
}      
   

public class SMSMessage implements MessageSendor {
    @Override
    public void send(PhoneContract phoneContract, String message) {
        sendMessage(phoneContract.getName(),phoneContract.getPhone(),message);
    }

    private void sendMessage(String name,String address,String message){
        System.out.println(String.format("%s sendMessage %s to %s %s.", this.getClass().getName(),message,name,address));
    }
}      
   

public class EmailMessage implements MessageSendor {
    @Override
    public void send(PhoneContract phoneContract, String message) {
        sendMessage(phoneContract.getName(),phoneContract.getEmail(),message);
    }

    private void sendMessage(String name,String address,String message){
        System.out.println(String.format("%s sendMessage %s to %s %s.", this.getClass().getName(),message,name,address));
    }
}
      
   

MessageClient 类      

public class MessageClient {
    public MessageSendor getMessageSendor() {
        return messageSendor;
    }

    public void setMessageSendor(MessageSendor messageSendor) {
        this.messageSendor = messageSendor;
    }

    private MessageSendor messageSendor;
    public MessageClient(MessageSendor sendor){
       setMessageSendor(sendor);
    }

    public void sendMessage(PhoneContract phoneContract,String message){
        if(null!=messageSendor){
            messageSendor.send(phoneContract, message);
        }
    }
}      
        
测试类：      
    
public class WorkClass {
    public void test() {
        PhoneContract phoneContract = new PhoneContract().setName("Jim").setPhone("[phone]").setEmail("[email protected]");
        MessageSendor messageSendor = new SMSMessage();
        MessageClient messageClient = new MessageClient(messageSendor);
        messageClient.sendMessage(phoneContract, "hello");
        messageClient.setMessageSendor(new EmailMessage());
        messageClient.sendMessage(phoneContract, "lunch");
    }
}      
   
        
测试输出：      
    
I/System.out: com.example.qinghua_liu.myapplication.designpatten.action.SMSMessage sendMessage hello to Jim [phone].
I/System.out: com.example.qinghua_liu.myapplication.designpatten.action.EmailMessage sendMessage lunch to Jim [email protected].