Realize channel routing based on policy mode

@Component
public class PayContextStrategy {
​
    private static  final String aliPay ="10001";
​
    private static  final String yinlian ="10002";
​
    // Containers : map
    private static Map<String, PayStrategy> strategyMap = new ConcurrentHashMap<>();
    // A static block  : static
    static {
        strategyMap.put(aliPay, new AliPayStrategy());
        strategyMap.put(yinlian, new YinLianPayStrategy());
    }
​
    // Get instance object 
    public static PayStrategy getInstance(String code) {
        return strategyMap.get(code);
    }
    
    public String toPay(String payCode){
        PayStrategy payStrategy = getInstance(payCode);
        if(payStrategy==null){
            return  " No information of this channel ";
        }
        return  payStrategy.toPay();
    }
}

@Component
public class AliPayStrategy   implements PayStrategy {
    public String toPay() {
        return " Call Alipay payment interface ...";
    }
}

/**
 *  UnionPay payment 
 */
@Component
public class YinLianPayStrategy implements PayStrategy {
    public String toPay() {
        return " Call UnionPay payment interface ...";
    }
}

@RestController
public class PayController {
    @Autowired
    private PayContextStrategy payContextStrategy;
    @RequestMapping("/toPay")
    public  String toPay(String payCode){
        if(StringUtils.isEmpty(payCode)){
            return " channel code Can't be empty !";
        }
        return payContextStrategy.toPay(payCode);
    }
​
}