设计模式笔记--策略

直接上课上的例子，我们购物后需要支付，支付方式可以有多种：支付宝，微信...

└── strategy
    ├── AliPay.java
    ├── Order.java
    ├── Payment.java
    ├── PayState.java
    ├── PayStrategyTest.java
    ├── PayType.java
    └── WechatPay.java

package com.xh.pattern.strategy;

/**
 * Created by root on 3/15/18.
 */
public class Order {
    private String uid;
    private String orderId;
    private double amount;

    public Order(String uid, String orderId, double amount) {
        this.uid = uid;
        this.orderId = orderId;
        this.amount = amount;
    }


    //这个参数，完全可以用Payment这个接口来代替
    //为什么？

    //完美地解决了switch的过程，不需要在代码逻辑中写switch了
    //更不需要写if    else if
    public PayState pay(PayType payType) {
        return payType.get().pay(this.uid, this.amount);
    }


}

package com.xh.pattern.strategy;

/**
 * Created by root on 3/15/18.
 */
public interface Payment {
    public PayState pay(String uid, double amount);
}

package com.xh.pattern.strategy;

/**
 * Created by root on 3/15/18.
 */
public enum PayType {
    ALI_PAY(new AliPay()),
    WECHAT_PAY(new WechatPay());


    private Payment payment;

    PayType(Payment payment) {
        this.payment = payment;
    }

    public Payment get() {
        return this.payment;
    }

}

package com.xh.pattern.strategy;

/**
 * Created by root on 3/15/18.
 */
public class PayState {
    private int code;
    private Object data;
    private String msg;

    public PayState(int code, String msg, Object data) {
        this.code = code;
        this.data = data;
        this.msg = msg;
    }

    public String toString() {
        return ("支付状态：[" + code + "]," + msg + ",交易详情：" + data);
    }

}

package com.xh.pattern.strategy;

/**
 * Created by root on 3/15/18.
 */
public class AliPay implements Payment {

    @Override
    public PayState pay(String uid, double amount) {
        System.out.println("欢迎使用支付宝");
        System.out.println("查询账户余额，开始扣款");
        return new PayState(200,"支付成功",amount);
    }
}

package com.xh.pattern.strategy;

/**
 * Created by root on 3/15/18.
 */
public class WechatPay implements Payment {
    @Override
    public PayState pay(String uid, double amount) {
        System.out.println("欢迎使用微信支付");
        System.out.println("直接从微信红包扣款");
        return new PayState(200, "支付成功", amount);
    }

}

package com.xh.pattern.strategy;

/**
 * Created by root on 3/15/18.
 */
public class PayStrategyTest {
    public static void main(String[] args) {
        //省略把商品添加到购物车，再从购物车下单
        //直接从点单开始
        Order order = new Order("1", "20180311001000009", 324.45);

        //开始支付，选择微信支付、支付宝、银联卡、京东白条、财付通
        //每个渠道它支付的具体算法是不一样的
        //基本算法固定的

        //这个值是在支付的时候才决定用哪个值
        System.out.println(order.pay(PayType.WECHAT_PAY));


    }
}