spring扩展之基于HandlerMapping实现接口灰度发布的demo

柔情只为你懂 2023-09-26 17:19 40阅读 0赞

## 背景 ##

面试经常被问到，你了解spring源码吗？有基于spring做过什么扩展吗？除了PropertyPlaceholderConfigurer处理占位符(被说烂了)还有其他的吗？

看了springmvc的源码，有了一个新的案例可讲(吹)

> 基于HandlerMapping实现接口灰度发布

说这个之前可以先铺垫一下，将故事讲的生动一点，我们来简单模拟一下。

面试官：“简历上说你对spring源码比较熟悉，能简单讲讲你对ioc、aop的理解吗？”

张三：“ioc是……aop是……巴拉巴拉”

(背了一大段八股文，毫无新意，面试官面无表情，然后打断张三，继续问)

面试官：你说对spring源码很熟悉，有多熟悉，在实际开发中有用过？扩展过吗？

张三：“有过呀，当时有个系统，升级改动比较大，对于同一批接口，老用户和新用户返回的数据不一样，为了实现系统的最小化改动，我当时就用spring的HandlerMapping解决了这个问题，前端访问的接口不变，只在参数中加一个接口版本号，就能实现灰度……，具体实现是这样的”

## 实现方案 ##

### 自定义注解 ###

新增一个自定义注解，用来标注接口的适配的版本号，默认为1.0版本

package com.fast.alibaba.annotation;
    
    import java.lang.annotation.*;
    
    /**
     * 自定义版本号注解
     */
    @Documented
    @Target({ElementType.TYPE,ElementType.METHOD})
    @Retention(RetentionPolicy.RUNTIME)
    public @interface ApiVersion {
    
        double value() default 1.0;
    }

### 自定义HandleMapping ###

自定义HandleMapping，继承spring家的HandleMapping，并重写两个getCustomTypeCondition方法

package com.fast.alibaba.handlemapping;
    
    import com.fast.alibaba.annotation.ApiVersion;
    import com.fast.alibaba.condition.ApiVersionRequestCondition;
    import org.springframework.core.annotation.AnnotationUtils;
    import org.springframework.web.servlet.mvc.condition.RequestCondition;
    import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
    
    import java.lang.reflect.Method;
    
    public class ApiVersionHandleMapping extends RequestMappingHandlerMapping {
    
    
        @Override
        protected RequestCondition<?> getCustomTypeCondition(Class<?> handlerType) {
            ApiVersion apiVersion = AnnotationUtils.getAnnotation(handlerType, ApiVersion.class);
            return new ApiVersionRequestCondition(apiVersion != null ? apiVersion.value() : 1.0);
        }
    
    
        @Override
        protected RequestCondition<?> getCustomMethodCondition(Method method) {
            ApiVersion apiVersion = AnnotationUtils.getAnnotation(method, ApiVersion.class);
            if(apiVersion == null){
                apiVersion = AnnotationUtils.getAnnotation(method.getDeclaringClass(), ApiVersion.class);
            }
            return new ApiVersionRequestCondition(apiVersion != null ? apiVersion.value() : 1.0);
        }
    }

### 实现RequestCondition接口 ###

以便识别前端传送的版本与接口上注解版本匹配

package com.fast.alibaba.condition;
    
    import com.alibaba.cloud.commons.lang.StringUtils;
    import org.springframework.web.servlet.mvc.condition.RequestCondition;
    
    import javax.servlet.http.HttpServletRequest;
    
    public class ApiVersionRequestCondition implements RequestCondition<ApiVersionRequestCondition> {
        private double apiVersion = 1.0;
    
        private static final String VERSION_NAME = "api-version";
    
        public double getApiVersion() {
            return apiVersion;
        }
    
        public ApiVersionRequestCondition(double apiVersion){
            this.apiVersion=apiVersion;
        }
    
        @Override
        public ApiVersionRequestCondition combine(ApiVersionRequestCondition method) {
            return method;
        }
    
        @Override
        public int compareTo(ApiVersionRequestCondition other, HttpServletRequest request) {
            return Double.compare(other.getApiVersion(),this.getApiVersion());
        }
    
        @Override
        public ApiVersionRequestCondition getMatchingCondition(HttpServletRequest request) {
    
            double reqVersionDouble = 1.0;
    
            String reqVersion = request.getHeader(VERSION_NAME);
            if(StringUtils.isEmpty(reqVersion)){
                reqVersion = request.getParameter(VERSION_NAME);
            }
    
            if(!StringUtils.isEmpty(reqVersion)){
                reqVersionDouble = Double.parseDouble(reqVersion);
            }
    
            if(this.getApiVersion() == reqVersionDouble){
                return this;
            }
            return null;
        }
    }

### 自定义WebMvcRegistrations ###

package com.fast.alibaba.register;
    
    import com.fast.alibaba.handlemapping.ApiVersionHandleMapping;
    import org.springframework.boot.autoconfigure.web.servlet.WebMvcRegistrations;
    import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
    
    /**
     * 注册自定义的 ApiVersionHandleMapping
     */
    public class ApiVersionMappingRegister implements WebMvcRegistrations {
    
        @Override
        public RequestMappingHandlerMapping getRequestMappingHandlerMapping() {
            return new ApiVersionHandleMapping();
        }
    }

### 注入WebMvcRegistrations ###

package com.fast.alibaba.config;
    
    import com.fast.alibaba.register.ApiVersionMappingRegister;
    import org.springframework.boot.autoconfigure.web.servlet.WebMvcRegistrations;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    @Configuration
    public class BaseConfiguration {
        @Bean
        public WebMvcRegistrations getWebMvcRegistrations(){
            return new ApiVersionMappingRegister();
        }
    }

### 测试类 ###

package com.fast.alibaba.controller;
    
    import com.fast.alibaba.annotation.ApiVersion;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class TestHandlerMappingController {
    
    
    
        @GetMapping("/getInfo")
        @ApiVersion(1.0)
        public String getSomeInfoByV1(){
    
            return "version 1.0";
        }
    
    
        @GetMapping("/getInfo")
        @ApiVersion(2.0)
        public String getSomeInfoByV2(){
    
            return "version 2.0";
        }
    
    
        @GetMapping("/getInfo")
        @ApiVersion(3.0)
        public String getSomeInfoByV3(){
    
            return "version 3.0";
        }
    
    }

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面试官：“还算有点东西，你回去等通知吧”

[b89a5c92394f4aafba1dbdfabf995a04.png]: https://img-blog.csdnimg.cn/b89a5c92394f4aafba1dbdfabf995a04.png
[5e3537e5dc574b5599b96e6613a01a35.png]: https://img-blog.csdnimg.cn/5e3537e5dc574b5599b96e6613a01a35.png
[63647faa725c4b7ba28e25736f06c91c.png]: https://img-blog.csdnimg.cn/63647faa725c4b7ba28e25736f06c91c.png