使用枚举和反射、策略模式，去掉过多的if else

Author: enjoyCoding666

src/main/java/com/enumdemo/pay/Client.java

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+package com.enumdemo.pay;
+
+import com.enumdemo.pay.service.Alipay;
+import com.enumdemo.pay.service.EbankPay;
+import com.enumdemo.pay.service.PayService;
+import com.enumdemo.pay.service.WechatPay;
+
+/**
+ * @Author: EnjoyCoding
+ * @Date: 2020\1\13 0013 21:14
+ * @Description:
+ * 详情参见： https://blog.csdn.net/u012557814/article/details/81671928
+ */
+public class Client {
+
+    public static void main(String[] args) throws Exception {
+        String payType="1";
+//        String payType = "ALIPAY";
+//        String payType  = "2";
+//        String payType  = "3";
+
+
+//        if("1".equals(payType)) {
+//            PayService pay=new Alipay();
+//        } else if("2".equals(payType)) {
+//            PayService pay=new WechatPay();
+//        } else if ("3".equals(payType)) {
+//            PayService pay=new EbankPay();
+//        }
+        //以上代码存在过多的if else判断，可以通过策略模式简化。
+        PayService strategy = PayStrategy.getPayStrategy(payType);
+        strategy.pay(12);
+
+    }
+
+}

src/main/java/com/enumdemo/pay/PayEnum.java

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+package com.enumdemo.pay;
+
+/**
+ * @Auther: Administrator
+ * @Date: 2020\1\13 0013 20:38
+ * @Description:
+ */
+public enum PayEnum {
+    /**
+     *  枚举常量对应的className，根据项目类的路径设置
+     *
+     */
+    ALIPAY("1","com.enumdemo.pay.service.Alipay"),
+    WECHATPAY("2","com.enumdemo.pay.service.WechatPay"),
+    EBANKPAY("3","com.enumdemo.pay.service.EbankPay")
+
+    ;
+
+    private String payClassName;
+    private String payType;
+
+
+
+    PayEnum(String payType, String payClassName) {
+        this.setPayClassName(payClassName);
+        this.setPayType(payType);
+    }
+
+    public String getPayClassName() {
+        return payClassName;
+    }
+
+    public void setPayClassName(String payClassName) {
+        this.payClassName = payClassName;
+    }
+
+    public void setPayType(String payType) {
+        this.payType = payType;
+    }
+
+    public String getPayType() {
+        return payType;
+    }
+
+    /**
+     * 根据支付类型，得到对应的支付类的路径
+     *
+     * @param payType
+     * @return
+     */
+    public static String getPayClassNameByType(String payType) {
+        for (PayEnum payEnum : PayEnum.values()) {
+            if (payEnum.getPayType().equals(payType)) {
+                return payEnum.getPayClassName();
+            }
+        }
+        return null;
+    }
+
+}

src/main/java/com/enumdemo/pay/PayStrategy.java

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+package com.enumdemo.pay;
+
+import com.enumdemo.pay.service.PayService;
+
+/**
+ * @Author: EnjoyCoding
+ * @Date: 2020\1\13 0013 20:40
+ * @Description:
+ *
+ */
+public class PayStrategy {
+
+    public static PayService getPayStrategy(String payType) throws Exception {
+        //valueOf()方法，可以通过枚举常量的名称(比如ALIPAY)，得到枚举常量。再通过枚举常量得到支付类的路径
+//        String payClassName = PayEnum.valueOf(payType).getPayClassName();
+        //直接根据支付类型，获取对应的支付类的路径
+        String payClassName= PayEnum.getPayClassNameByType(payType);
+        //根据类名进行反射，生成对象
+        return (PayService) Class.forName(payClassName).newInstance();
+    }
+
+}

src/main/java/com/enumdemo/pay/service/Alipay.java

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+package com.enumdemo.pay.service;
+
+/**
+ * @Author: EnjoyCoding
+ * @Date: 20:51 2020\1\13 0013
+ * @Description:
+ */
+public class Alipay implements PayService {
+
+    public void pay(double total) {
+        System.out.println("pay with alipay: " + total);
+    }
+
+}

src/main/java/com/enumdemo/pay/service/EbankPay.java

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+package com.enumdemo.pay.service;
+
+/**
+ * @Author: EnjoyCoding
+ * @Date: 2020\1\13 0013 20:55
+ * @Description:
+ */
+public class EbankPay implements PayService {
+
+    public void pay(double total) {
+        System.out.println("pay with ebankPay: " + total);
+    }
+
+}

src/main/java/com/enumdemo/pay/service/PayService.java

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+package com.enumdemo.pay.service;
+
+/**
+ * @Auther: Administrator
+ * @Date: 2020\1\13 0013 20:50
+ * @Description:
+ */
+public interface PayService {
+
+    void pay(double total);
+
+}
+

src/main/java/com/enumdemo/pay/service/WechatPay.java

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+package com.enumdemo.pay.service;
+
+/**
+ * @Author: EnjoyCoding
+ * @Date: 2020\1\13 0013 20:53
+ * @Description:
+ */
+public class WechatPay implements PayService {
+
+    public void pay(double total) {
+        System.out.println("pay with wechatpay: " + total);
+    }
+
+}