简介

现在项目中大部分采用前后端分离的架构，采用这种架构的项目，在返回数据时，几乎都是采用返回 json 格式的数据。而 spring 中返回 json 格式的数据一般采用 @RestController 或者 @ResponseBody 注解。代码样例

@ResponseBody

@RequestMapping("/reqBody")

public ResultInfo<Map<String, Object>> reqBody(){

		ResultInfo<Map<String, Object>> resultInfo = new ResultInfo<>();

		resultInfo.setCode(200);

		resultInfo.setMessage("success");

		Map<String, Object> map = new HashMap<>();

		map.put("userId", 100);

		map.put("tenantId", 1001);

		map.put("userName", "bug弄潮儿");

		resultInfo.setBody(map);

		return resultInfo;

	}

今天定义一个注解读返回的 json 进行加密，来运用 HandlerMethodReturnValueHandler

pom.xml 文件引入依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

	<modelVersion>4.0.0</modelVersion>

	<groupId>com.olive</groupId>

	<artifactId>springmvc-response-body</artifactId>

	<version>0.0.1-SNAPSHOT</version>

	<packaging>jar</packaging>

	<name>springmvc-response-body</name>

	<url>http://maven.apache.org</url>

	<parent>

		<groupId>org.springframework.boot</groupId>

		<artifactId>spring-boot-starter-parent</artifactId>

		<version>2.5.14</version>

		<relativePath /> <!-- lookup parent from repository -->

	</parent>

	<properties>

		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

		<maven.compiler.source>8</maven.compiler.source>

		<maven.compiler.target>8</maven.compiler.target>

	</properties>

	<dependencies>

		<dependency>

			<groupId>org.springframework.boot</groupId>

			<artifactId>spring-boot-starter-test</artifactId>

			<scope>test</scope>

		</dependency>

		<dependency>

			<groupId>org.projectlombok</groupId>

			<artifactId>lombok</artifactId>

		</dependency>

		<dependency>

		    <groupId>org.springframework.boot</groupId>

		    <artifactId>spring-boot-starter-web</artifactId>

		</dependency>

		<dependency>

			<groupId>com.alibaba.fastjson2</groupId>

			<artifactId>fastjson2</artifactId>

			<version>2.0.14</version>

		</dependency>

	</dependencies>

</project>

定义加密注解

package com.olive.annotation;

import java.lang.annotation.*;

@Target({ElementType.TYPE, ElementType.METHOD})

@Retention(RetentionPolicy.RUNTIME)

@Documented

public @interface Encrypted {

    boolean value() default true;

}

Encrypted 注解，该注解是一个标识注解；如果打上该注解标识加密

统一返回定义

主要包含 code、message 和 body 属性定义

package com.olive.dto;

import lombok.Data;

import java.io.Serializable;

@Data

public class ResultInfo<T> implements Serializable {

    public  int code;

    public String message;

    private T body;

    private boolean encrypt;

}

自定义 ResponseBodyHandler

该类实现 HandlerMethodReturnValueHandler 类，主要对 @RestController 或者 @ResponseBody 注解进行解析

package com.olive.config;

import com.alibaba.fastjson2.JSON;

import com.olive.annotation.Encrypted;

import com.olive.dto.ResultInfo;

import org.springframework.core.MethodParameter;

import org.springframework.core.annotation.AnnotatedElementUtils;

import org.springframework.util.Base64Utils;

import org.springframework.web.bind.annotation.ResponseBody;

import org.springframework.web.context.request.NativeWebRequest;

import org.springframework.web.method.support.HandlerMethodReturnValueHandler;

import org.springframework.web.method.support.ModelAndViewContainer;

import java.nio.charset.StandardCharsets;

public class ResponseBodyHandler implements HandlerMethodReturnValueHandler {

    protected final HandlerMethodReturnValueHandler handlerMethodReturnValueHandler;

    public ResponseBodyHandler(HandlerMethodReturnValueHandler handlerMethodReturnValueHandler){

        this.handlerMethodReturnValueHandler = handlerMethodReturnValueHandler;

    }

    @Override

    public boolean supportsReturnType(MethodParameter returnType) {

        //如果被@ResponseBody注解修饰的 返回true

        return (AnnotatedElementUtils.hasAnnotation(returnType.getContainingClass(), ResponseBody.class) || returnType.hasMethodAnnotation(ResponseBody.class))

                && returnType.hasMethodAnnotation(Encrypted.class);

    }

    @Override

    public void handleReturnValue(Object returnValue,

                                  MethodParameter returnType,

                                  ModelAndViewContainer mavContainer,

                                  NativeWebRequest webRequest) throws Exception {

        if(returnValue instanceof ResultInfo){

            ResultInfo<?> resultInfo = (ResultInfo<?>)returnValue;

            ResultInfo<String> newResultInfo = new ResultInfo<>();

            newResultInfo.setCode(resultInfo.getCode());

            newResultInfo.setMessage(resultInfo.getMessage());

            newResultInfo.setEncrypt(true);

            newResultInfo.setBody(Base64Utils.encodeToString(JSON.toJSONString(resultInfo.getBody()).getBytes(StandardCharsets.UTF_8)));

            //ResponseBody注解执行器

            handlerMethodReturnValueHandler.handleReturnValue(newResultInfo,

                    returnType, mavContainer, webRequest);

        }else{

            handlerMethodReturnValueHandler.handleReturnValue(returnValue,

                    returnType, mavContainer,  webRequest);

        }

    }

}

注册 ResponseBodyHandler 到 controller 返回值处理器里，即添加自己的返回值处理器

package com.olive.config;

import org.springframework.beans.factory.InitializingBean;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.context.annotation.Configuration;

import org.springframework.web.method.support.HandlerMethodReturnValueHandler;

import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;

import org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor;

import java.util.ArrayList;

import java.util.List;

@Configuration

public class WebConfig implements InitializingBean {

    @Autowired

    private RequestMappingHandlerAdapter adapter;

    @Override

    public void afterPropertiesSet() throws Exception {

        List<HandlerMethodReturnValueHandler> unmodifiableList = adapter.getReturnValueHandlers();

        List<HandlerMethodReturnValueHandler> list = new ArrayList<>(unmodifiableList.size());

        for (HandlerMethodReturnValueHandler returnValueHandler : unmodifiableList) {

            if (returnValueHandler instanceof RequestResponseBodyMethodProcessor) {

                //将RequestResponseBodyMethodProcessor 实际返回值替换为自定义的，实际执行为RequestResponseBodyMethodProcessor

                //重要

                HandlerMethodReturnValueHandler handler = new ResponseBodyHandler(returnValueHandler);

                list.add(handler);

            } else {

                list.add(returnValueHandler);

            }

        }

        adapter.setReturnValueHandlers(list);

    }

}

测试

编写 Springboot 启动引导类

package com.olive;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

/**

 * https://cloud.tencent.com/developer/article/1616704

 *

 * @author 2230

 *

 */

@SpringBootApplication

public class Application {

    public static void main(String[] args) {

        SpringApplication.run(Application.class);

    }

}

编写测试 Controller

package com.olive.controller;

import java.util.HashMap;

import java.util.Map;

import com.olive.annotation.Encrypted;

import com.olive.dto.ResultInfo;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RestController;

@RestController

public class TestController {

	@Encrypted

	@RequestMapping("/reqBody")

	public ResultInfo<Map<String, Object>> reqBody(){

		ResultInfo<Map<String, Object>> resultInfo = new ResultInfo<>();

		resultInfo.setCode(200);

		resultInfo.setMessage("success");

		Map<String, Object> map = new HashMap<>();

		map.put("userId", 100);

		map.put("tenantId", 1001);

		map.put("userName", "bug弄潮儿");

		resultInfo.setBody(map);

		return resultInfo;

	}

}

通过 HandlerMethodReturnValueHandler 可以对返回的数据进行进一步的封装，减少在业务代码中进行重复的返回值处理。例如，文章中的对返回数据进行统一加密。

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