场景
在支付选择中，可以选择京东白条、支付宝、微信、银联支付等。
public void payment(String payType
) {
if (payType
.equals("JD")) {
} else if (payType
.equals("Alibaba")) {
} else if (payType
.equals("Tecent")) {
} else if (payType
.equals("Union")) {
} else {
}
}
解决方案
工厂设计模式+策略模式+单例模式，UML图如下：
策略
public abstract class PaymentStrategy {
public abstract String
getName();
protected abstract double queryBalance(String uid
);
public MsgResult
pay(String uid
, double amount
) {
if (queryBalance(uid
) < amount
) {
return new MsgResult(500, "支付失败", "余额不足");
}
return new MsgResult(200, "支付成功", "支付余额: " + (queryBalance(uid
) - amount
));
}
}
public class UnionPayStrategy extends PaymentStrategy {
@Override
public String
getName() {
return "银联支付";
}
@Override
protected double queryBalance(String uid
) {
return 100;
}
}
public class TecentPayStrategy extends PaymentStrategy {
@Override
public String
getName() {
return "微信支付";
}
@Override
protected double queryBalance(String uid
) {
return 1000;
}
}
public class JdPayStrategy extends PaymentStrategy {
@Override
public String
getName() {
return "京东白条";
}
@Override
protected double queryBalance(String uid
) {
return 1000;
}
}
public class AlibabaPayStrategy extends PaymentStrategy {
@Override
public String
getName() {
return "支付宝支付";
}
@Override
protected double queryBalance(String uid
) {
return 1000;
}
}
枚举
public enum PaymentEnum
{
ALIBABA("ALIBABA", new AlibabaPayStrategy()),
JD("JD", new JdPayStrategy()),
TECENT("TECENT", new TecentPayStrategy()),
UNION("UNION", new UnionPayStrategy()),
DEFAULT("DEFAULT", new AlibabaPayStrategy());
private final String payName
;
private final PaymentStrategy paymentStrategy
;
PaymentEnum(String payName
, PaymentStrategy paymentStrategy
) {
this.payName
= payName
;
this.paymentStrategy
= paymentStrategy
;
}
public String
getPayName() {
return payName
;
}
public PaymentStrategy
getPaymentStrategy() {
return paymentStrategy
;
}
}
工厂+单例
public class PaymentFactory {
private static Map
<String, PaymentStrategy> register
= new HashMap<>();
static {
for (PaymentEnum p
: PaymentEnum
.values()) {
register
.put(p
.getPayName(), p
.getPaymentStrategy());
}
}
public static PaymentStrategy
getInstance(String payType
) {
if (register
.containsKey(payType
)) {
return register
.get(payType
);
}
return PaymentEnum
.DEFAULT
.getPaymentStrategy();
}
}
业务类
@AllArgsConstructor
@Data
@NoArgsConstructor
@ToString
public class MsgResult {
private int code
;
private Object data
;
private String msg
;
}
@AllArgsConstructor
@Data
@NoArgsConstructor
@ToString
public class Order {
private String uid
;
private String orderId
;
private Double amount
;
public MsgResult
pay(String payType
) {
PaymentStrategy paymentStrategy
= PaymentFactory
.getInstance(payType
);
System
.out
.println("欢迎使用" + paymentStrategy
.getName());
System
.out
.println("本次交易金额为：" + amount
+ ",....开始扣款");
return paymentStrategy
.pay(uid
,amount
);
}
}
测试类
public class PayTest {
public static void main(String
[] args
) {
Order order
= new Order("6", "6", 500.0);
MsgResult msg
= order
.pay(PaymentEnum
.ALIBABA
.getPayName());
System
.out
.println(msg
.toString());
}
}
