使用注解 + 策略模式，减少代码中的if/switch语句，增加代码灵活性

你的名字 2022-03-12 11:48 192阅读 0赞

## 需求描述 ##

现在我们有一个接受供应商订单状态通知的接口，目前支持的功能有退款，改签，后续可能需要接入新功能，比如航变，订单状态改变之类。接口的请求格式一致，接口如下：

请求

package com.ahut.contract.flight;
    
    /**
     * @desc : 供应商通知请求
     * @author : cheng
     * @date : 2019-03-04 21:18
     */
    public class VendorOrderNotifyRequest {
    
        /**
         * 数据
         */
        private String data;
        /**
         * 依据tag判断事件类型
         */
        private String tag;
        /**
         * 创建时间
         */
        private long createTime;
        /**
         * 签名
         */
        private String sign;
    
        public String getData() {
            return data;
        }
    
        public void setData(String data) {
            this.data = data;
        }
    
        public String getTag() {
            return tag;
        }
    
        public void setTag(String tag) {
            this.tag = tag;
        }
    
        public long getCreateTime() {
            return createTime;
        }
    
        public void setCreateTime(long createTime) {
            this.createTime = createTime;
        }
    
        public String getSign() {
            return sign;
        }
    
        public void setSign(String sign) {
            this.sign = sign;
        }
    }

响应

package com.ahut.contract.flight;
    
    /**
     * @desc : 供应商通知响应
     * @author : cheng
     * @date : 2019-03-04 21:21
     */
    public class VendorOrderNotifyResponse {
    
        private int code;
    
        private String message;
    
        public int getCode() {
            return code;
        }
    
        public void setCode(int code) {
            this.code = code;
        }
    
        public String getMessage() {
            return message;
        }
    
        public void setMessage(String message) {
            this.message = message;
        }
    }

请求统一入口接口

package com.ahut.flight.service;
    
    import com.ahut.contract.flight.VendorOrderNotifyRequest;
    import com.ahut.contract.flight.VendorOrderNotifyResponse;
    
    /**
     * @desc :
     * @author : cheng
     * @date : 2019-03-04 21:16
     */
    public interface VendorOrderNotifyService {
    
        /**
         * @desc : 
         * @author : cheng
         * @date : 2019-03-04 21:24
         */
        VendorOrderNotifyResponse orderNotify(VendorOrderNotifyRequest request);
    
    }

## 使用if/switch ##

package com.ahut.flight.service.impl;
    
    import com.ahut.contract.flight.VendorOrderNotifyRequest;
    import com.ahut.contract.flight.VendorOrderNotifyResponse;
    import com.ahut.flight.service.OrderNotifyContextService;
    import com.ahut.flight.service.OrderNotifyHandleService;
    import com.ahut.flight.service.VendorOrderNotifyService;
    import org.apache.commons.lang3.StringUtils;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import java.util.Optional;
    
    @Service
    public class VendorOrderNotifyServiceImpl implements VendorOrderNotifyService {
    
        /**
         * @desc :
         * @author : cheng
         * @date : 2019-03-04 21:25
         */
        @Override
        public VendorOrderNotifyResponse orderNotify(VendorOrderNotifyRequest request) {
            String tag = Optional.ofNullable(request).map(VendorOrderNotifyRequest::getTag).orElse("");
            if (StringUtils.equals(tag, "change")) {
                // 改签
            } else if (StringUtils.equals(tag, "refund")) {
                // 退款
            } else {
                // 不支持
            }
    
            switch (tag) {
                case "change":
                    // 改签
                    break;
                case "refund":
                    // 退款
                    break;
                    default:
                        // 不支持
            }
            return null;
        }
    
    }

**缺点：代码不灵活，下次新增功能时，需要修改现有代码（增加if分支或者switch分支）**

## 使用注解 + 策略模式 ##

定义注解

package com.ahut.common.annotation;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    /**
     * @desc :
     * @author : cheng
     * @date : 2019-03-04 21:56
     */
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface RequestTag {
    
        public String value() default "";
    
    }

定义处理请求data的统一接口

package com.ahut.flight.service;
    
    import com.ahut.contract.flight.VendorOrderNotifyResponse;
    
    /**
     * @desc : 处理请求
     * @author : cheng
     * @date : 2019-03-04 21:29
     */
    public interface OrderNotifyHandleService {
    
        /**
         * @desc :
         * @author : cheng
         * @date : 2019-03-04 21:46
         */
        VendorOrderNotifyResponse orderNotify(String data);
    
    }

实现统一接口，退款，使用自定义注解

package com.ahut.flight.service.impl;
    
    
    import com.ahut.common.annotation.RequestTag;
    import com.ahut.contract.flight.VendorOrderNotifyResponse;
    import com.ahut.flight.service.OrderNotifyHandleService;
    import org.springframework.stereotype.Service;
    
    /**
     * @desc : 退款
     * @author : cheng
     * @date : 2019-03-04 21:50
     */
    @Service("RefundNotifyHandleServiceImpl")
    @RequestTag("refund")
    public class RefundNotifyHandleServiceImpl implements OrderNotifyHandleService {
    
        /**
         * @desc : 
         * @author : cheng
         * @date : 2019-03-04 22:11
         */
        @Override
        public VendorOrderNotifyResponse orderNotify(String data) {
            VendorOrderNotifyResponse response = new VendorOrderNotifyResponse();
            response.setCode(0);
            response.setMessage("处理退票通知");
            return response;
        }
    }

实现统一接口，改签，使用自定义注解

package com.ahut.flight.service.impl;
    
    import com.ahut.common.annotation.RequestTag;
    import com.ahut.contract.flight.VendorOrderNotifyResponse;
    import com.ahut.flight.service.OrderNotifyHandleService;
    import org.springframework.stereotype.Service;
    
    /**
     * @desc : 改签
     * @author : cheng
     * @date : 2019-03-04 21:50
     */
    @Service("ChangeNotifyHandleServiceImpl")
    @RequestTag("change")
    public class ChangeNotifyHandleServiceImpl implements OrderNotifyHandleService {
    
        /**
         * @desc :
         * @author : cheng
         * @date : 2019-03-04 22:04
         */
        @Override
        public VendorOrderNotifyResponse orderNotify(String data) {
            VendorOrderNotifyResponse response = new VendorOrderNotifyResponse();
            response.setCode(0);
            response.setMessage("处理改签通知");
            return response;
        }
    }

实现统一接口，不支持的tag，使用自定义注解

package com.ahut.flight.service.impl;
    
    import com.ahut.common.annotation.RequestTag;
    import com.ahut.contract.flight.VendorOrderNotifyResponse;
    import com.ahut.flight.service.OrderNotifyHandleService;
    import org.springframework.stereotype.Service;
    
    /**
     * @desc : 不支持
     * @author : cheng
     * @date : 2019-03-05 22:11
     */
    @Service("NonSupportNotifyHandleServiceImpl")
    @RequestTag("nonsupport")
    public class NonSupportNotifyHandleServiceImpl implements OrderNotifyHandleService {
    
        /**
         * @desc :
         * @author : cheng
         * @date : 2019-03-05 22:12
         */
        @Override
        public VendorOrderNotifyResponse orderNotify(String data) {
            VendorOrderNotifyResponse response = new VendorOrderNotifyResponse();
            response.setCode(0);
            response.setMessage("不支持的通知");
            return response;
        }
    }

定义上下文接口，依据tag，返回具体的处理实例

package com.ahut.flight.service;
    
    /**
     * @desc : 上下文
     * @author : cheng
     * @date : 2019-03-04 21:27
     */
    public interface OrderNotifyContextService {
    
        /**
         * @desc :
         * @author : cheng
         * @date : 2019-03-04 22:04
         */
        OrderNotifyHandleService getContext(String tag);
    
    }

上下文实现

package com.ahut.flight.service.impl;
    
    import com.ahut.common.annotation.RequestTag;
    import com.ahut.flight.service.OrderNotifyContextService;
    import com.ahut.flight.service.OrderNotifyHandleService;
    import org.apache.commons.lang3.StringUtils;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import javax.annotation.Resource;
    import java.util.List;
    
    /**
     * @desc : 上下文
     * @author : cheng
     * @date : 2019-03-04 22:05
     */
    @Service
    public class OrderNotifyContextServiceImpl implements OrderNotifyContextService {
    
        @Autowired
        private List<OrderNotifyHandleService> handleServiceList;
    
        @Resource(name = "NonSupportNotifyHandleServiceImpl")
        private OrderNotifyHandleService nonsupportService;
    
        @Override
        public OrderNotifyHandleService getContext(String tag) {
            if (StringUtils.isBlank(tag)) {
                return nonsupportService;
            }
    
    		// 对比注解中的value和tag
            OrderNotifyHandleService handleService = handleServiceList.stream()
                    .filter(f -> StringUtils.equals(tag, f.getClass().getAnnotation(RequestTag.class).value()))
                    .findFirst()
                    .orElse(nonsupportService);
    
            return handleService;
        }
    }

实现请求统一入口

package com.ahut.flight.service.impl;
    
    import com.ahut.contract.flight.VendorOrderNotifyRequest;
    import com.ahut.contract.flight.VendorOrderNotifyResponse;
    import com.ahut.flight.service.OrderNotifyContextService;
    import com.ahut.flight.service.OrderNotifyHandleService;
    import com.ahut.flight.service.VendorOrderNotifyService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import java.util.Optional;
    
    @Service
    public class VendorOrderNotifyServiceImpl implements VendorOrderNotifyService {
    
    	/**
    	 * 持有上下文
    	 */
        @Autowired
        private OrderNotifyContextService contextService;
    
        /**
         * @desc :
         * @author : cheng
         * @date : 2019-03-04 21:25
         */
        @Override
        public VendorOrderNotifyResponse orderNotify(VendorOrderNotifyRequest request) {
            String tag = Optional.ofNullable(request).map(VendorOrderNotifyRequest::getTag).orElse("");
            OrderNotifyHandleService handleService = contextService.getContext(tag);
            VendorOrderNotifyResponse response = handleService.orderNotify(request.getData());
            return response;
        }
    
    }

## 总结 ##

1.  增加了代码的灵活性
2.  符合开闭原则
3.  新增功能时，不用修改原有的代码，直接实现接口即可