SpringBoot实战 - 接口响应体统一封装

前言

在之前的文章中我们有介绍过，如何更好、更简单的写好一个接口《接口返回值》，今天的这篇文章我们主要介绍，怎么统一处理下接口的返回格式问题。

问题分析

我们先来分析下我们所面临的问题在哪里，然后接着给出解决方案。在写一个接口时，我们通常会先统一定义一下接口的返回格式是什么，然后在跟前端去对接，通常的返回格式大体两种(我们以保存用户为例)：

1.成功/失败响应格式不一致（此种方式作为我们默认的接口响应方式）

保存用户成功，响应体：

{
    "id": 10000,
    "pwd": "123123",
    "nickname": "nickname1",
    "img": "http://xxx.com/1.png",
    "status": "NORMAL",
    "createTime": 1517762718278
}

失败响应体（下面的格式是 spring boot 默认的错误响应格式，只不过我们在其基础上增加了一个 code 字段用于解释更详细的错误码）

{
    "status": 400,
    "error": "Bad Request",
    "message": "参数无效",
    "code": 10001,
    "path": "/user",
    "exception": "org.springframework.web.bind.MethodArgumentNotValidException",
    "errors": [
        {
            "fieldName": "status",
            "message": "值是无效的"
        }
    ],
    "timestamp": 1515076067369
}

2.成功/失败响应体格式一致

保存用户成功，响应体：

{
    "code": 1,
    "msg": "成功",
    "data": {
        "id": 10000,
        "pwd": "123123",
        "nickname": "nickname1",
        "img": "http://xxx.com/1.png",
        "status": "NORMAL",
        "createTime": 1515076287882
    }
}

失败响应体：

{
    "code": 10001,
    "msg": "参数无效",
    "data": [
        {
            "fieldName": "status",
            "message": "值是无效的"
        }
    ]
}

那么如果我们想要的响应体格式是第二种，我们该如何写我们的代码呢？你可能想是这样么？

@RestController
@RequestMapping("/user")
public class UserController {

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public PlatformResult addUser(@Validated @RequestBody User user) {
        user.setId("10000");
        user.setCreateTime(new Date());
        return PlatformResult.success(user);
    }

}

PlatformResult.success() 这段逻辑显然很多余，每个方法都要这样写一遍，所以上述方式并不是我们想要的，我们要的是

@ResponseResult(PlatformResult.class)
@RestController
@RequestMapping("/users")
public class UserController {

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public User addUser(@Validated @RequestBody User user) {
        user.setId("10000");
        user.setCreateTime(new Date());
        return user;
    }

}

我们加了一个自定义的注解 @ResponseResult(PlatformResult.class)，参数 PlatformResult.class 告诉这个 Controller 类下的所有方法都以这个类 PlatformResult 的格式进行返回，这个注解可以标记在类或方法上，好了，我们的目的明朗了许多，要做的就是标记这个注解让它实现接口返回值格式控制这个功能，下面我们给出具体的实现方式。

实现思路

首先介绍下完成我们这次主要功能的几个类：

Result 是返回格式类的父接口（所有返回格式类都需要继承它）

PlatformResult 通用返回结果格式（我们上面说的第二种返回结果）

DefaultErrorResult 全局错误返回结果（我们上面说的第一种错误时的返回结果）

GlobalExceptionHandler 全局异常处理

ResponseResult 注解类（用于在Controller上指定返回值格式类）

ResponseResultInterceptor 拦截器（主要用于将 ResponseResult 注解类的标记信息传入 ResponseResultHandler 中）

ResponseResultHandler 响应体格式处理器（主要转换逻辑都在这里）

代码实现

下面将有一大片代码袭来，要顶住！哈哈~

Result 接口类

package cn.notemi.demo.result;

import java.io.Serializable;

/**
 * @desc 响应格式父接口
 */
public interface Result extends Serializable {
}

说明

理论上所有的返回格式类都需要实现该接口才能被使用

PlatformResult 通用返回结果

package cn.notemi.demo.result;

import cn.notemi.demo.enums.ResultCode;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @desc 平台通用返回结果
 */
@Builder
@NoArgsConstructor
@AllArgsConstructor
@Data
public class PlatformResult implements Result {

    private static final long serialVersionUID = 874200365941306385L;

    private Integer code;

    private String msg;

    private Object data;

    public static PlatformResult success() {
        PlatformResult result = new PlatformResult();
        result.setResultCode(ResultCode.SUCCESS);
        return result;
    }

    public static PlatformResult success(Object data) {
        PlatformResult result = new PlatformResult();
        result.setResultCode(ResultCode.SUCCESS);
        result.setData(data);
        return result;
    }

    public static PlatformResult failure(ResultCode resultCode) {
        PlatformResult result = new PlatformResult();
        result.setResultCode(resultCode);
        return result;
    }

    public static PlatformResult failure(ResultCode resultCode, Object data) {
        PlatformResult result = new PlatformResult();
        result.setResultCode(resultCode);
        result.setData(data);
        return result;
    }

    public static PlatformResult failure(String message) {
        PlatformResult result = new PlatformResult();
        result.setCode(ResultCode.PARAM_IS_INVALID.code());
        result.setMsg(message);
        return result;
    }

    private void setResultCode(ResultCode code) {
        this.code = code.code();
        this.msg = code.message();
    }

}

DefaultErrorResult 默认全局错误返回格式

package cn.notemi.demo.result;

import cn.notemi.demo.enums.BusinessExceptionEnum;
import cn.notemi.demo.enums.ResultCode;
import cn.notemi.demo.exceptions.BusinessException;
import cn.notemi.demo.util.RequestContextUtil;
import cn.notemi.demo.util.StringUtil;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.http.HttpStatus;

import java.util.Date;

/**
 * @desc 默认全局错误返回结果
 *       备注：该返回信息是spring boot的默认异常时返回结果，目前也是我们服务的默认返回结果
 */
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Data
public class DefaultErrorResult implements Result {

    private static final long serialVersionUID = 1899083570489722793L;

    /**
     * HTTP响应状态码 {@link HttpStatus}
     */
    private Integer status;

    /**
     * HTTP响应状态码的英文提示
     */
    private String error;

    /**
     * 异常堆栈的精简信息
     * 
     */
    private String message;

    /**
     * 我们系统内部自定义的返回值编码，{@link ResultCode} 它是对错误更加详细的编码
     * 
     * 备注：spring boot默认返回异常时，该字段为null
     */
    private Integer code;

    /**
     * 调用接口路径
     */
    private String path;

    /**
     * 异常的名字
     */
    private String exception;

    /**
     * 异常的错误传递的数据
     */
    private Object errors;

    /**
     * 时间戳
     */
    private Date timestamp;

    public static DefaultErrorResult failure(ResultCode resultCode, Throwable e, HttpStatus httpStatus, Object errors) {
        DefaultErrorResult result = DefaultErrorResult.failure(resultCode, e, httpStatus);
        result.setErrors(errors);
        return result;
    }

    public static DefaultErrorResult failure(ResultCode resultCode, Throwable e, HttpStatus httpStatus) {
        DefaultErrorResult result = new DefaultErrorResult();
        result.setCode(resultCode.code());
        result.setMessage(resultCode.message());
        result.setStatus(httpStatus.value());
        result.setError(httpStatus.getReasonPhrase());
        result.setException(e.getClass().getName());
        String path = RequestContextUtil.getRequest().getRequestURI();
        result.setPath(path);
        result.setTimestamp(new Date());
        return result;
    }

    public static DefaultErrorResult failure(BusinessException e) {
        BusinessExceptionEnum ee = BusinessExceptionEnum.getByEClass(e.getClass());
        if (ee != null) {
            return DefaultErrorResult.failure(ee.getResultCode(), e, ee.getHttpStatus(), e.getData());
        }

        DefaultErrorResult defaultErrorResult = DefaultErrorResult.failure(e.getResultCode() == null ? ResultCode.SUCCESS : e.getResultCode(), e, HttpStatus.OK, e.getData());
        if (StringUtil.isNotEmpty(e.getMessage())) {
            defaultErrorResult.setMessage(e.getMessage());
        }
        return defaultErrorResult;
    }

}

GlobalExceptionHandler 全局错误异常处理器

package cn.notemi.demo.handler;

import cn.notemi.demo.exceptions.BusinessException;
import cn.notemi.demo.result.DefaultErrorResult;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.validation.BindException;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpServletRequest;
import javax.validation.ConstraintViolationException;

/**
 * @desc 统一异常处理器
 */
@RestController
@ControllerAdvice
public class GlobalExceptionHandler extends BaseGlobalExceptionHandler {

    /** 处理400类异常 */
    @Override
    @ResponseStatus(HttpStatus.BAD_REQUEST)
    @ExceptionHandler(ConstraintViolationException.class)
    public DefaultErrorResult handleConstraintViolationException(ConstraintViolationException e, HttpServletRequest request) {
        return super.handleConstraintViolationException(e, request);
    }

    @Override
    @ResponseStatus(HttpStatus.BAD_REQUEST)
    @ExceptionHandler(HttpMessageNotReadableException.class)
    public DefaultErrorResult handleConstraintViolationException(HttpMessageNotReadableException e, HttpServletRequest request) {
        return super.handleConstraintViolationException(e, request);
    }

    @Override
    @ResponseStatus(HttpStatus.BAD_REQUEST)
    @ExceptionHandler(BindException.class)
    public DefaultErrorResult handleBindException(BindException e, HttpServletRequest request) {
        return super.handleBindException(e, request);
    }

    @Override
    @ResponseStatus(HttpStatus.BAD_REQUEST)
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public DefaultErrorResult handleMethodArgumentNotValidException(MethodArgumentNotValidException e, HttpServletRequest request) {
        return super.handleMethodArgumentNotValidException(e, request);
    }

    /** 处理自定义异常 */
    @Override
    @ExceptionHandler(BusinessException.class)
    public ResponseEntity<DefaultErrorResult> handleBusinessException(BusinessException e, HttpServletRequest request) {
        return super.handleBusinessException(e, request);
    }

    /** 处理运行时异常 */
    @Override
    @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
    @ExceptionHandler(Throwable.class)
    public DefaultErrorResult handleThrowable(Throwable e, HttpServletRequest request) {
        //TODO 可通过邮件、微信公众号等方式发送信息至开发人员、记录存档等操作
        return super.handleThrowable(e, request);
    }

}

BaseGlobalExceptionHandler 全局异常处理基础类

package cn.notemi.demo.handler;

import cn.notemi.demo.enums.ResultCode;
import cn.notemi.demo.exceptions.BusinessException;
import cn.notemi.demo.helper.ParameterInvalidItemHelper;
import cn.notemi.demo.model.bo.ParameterInvalidItem;
import cn.notemi.demo.result.DefaultErrorResult;
import lombok.extern.slf4j.Slf4j;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.validation.BindException;
import org.springframework.web.bind.MethodArgumentNotValidException;

import javax.servlet.http.HttpServletRequest;
import javax.validation.ConstraintViolationException;
import java.util.List;

/**
 * @desc 全局异常处理基础类
 */
@Slf4j
public abstract class BaseGlobalExceptionHandler {

    /**
     * 违反约束异常
     */
    protected DefaultErrorResult handleConstraintViolationException(ConstraintViolationException e, HttpServletRequest request) {
        log.info("handleConstraintViolationException start, uri:{}, caused by: ", request.getRequestURI(), e);
        List<ParameterInvalidItem> parameterInvalidItemList = ParameterInvalidItemHelper.convertCVSetToParameterInvalidItemList(e.getConstraintViolations());
        return DefaultErrorResult.failure(ResultCode.PARAM_IS_INVALID, e, HttpStatus.BAD_REQUEST, parameterInvalidItemList);
    }

    /**
     * 处理验证参数封装错误时异常
     */
    protected DefaultErrorResult handleConstraintViolationException(HttpMessageNotReadableException e, HttpServletRequest request) {
        log.info("handleConstraintViolationException start, uri:{}, caused by: ", request.getRequestURI(), e);
        return DefaultErrorResult.failure(ResultCode.PARAM_IS_INVALID, e, HttpStatus.BAD_REQUEST);
    }

    /**
     * 处理参数绑定时异常（反400错误码）
     */
    protected DefaultErrorResult handleBindException(BindException e, HttpServletRequest request) {
        log.info("handleBindException start, uri:{}, caused by: ", request.getRequestURI(), e);
        List<ParameterInvalidItem> parameterInvalidItemList = ParameterInvalidItemHelper.convertBindingResultToMapParameterInvalidItemList(e.getBindingResult());
        return DefaultErrorResult.failure(ResultCode.PARAM_IS_INVALID, e, HttpStatus.BAD_REQUEST, parameterInvalidItemList);
    }

    /**
     * 处理使用@Validated注解时，参数验证错误异常（反400错误码）
     */
    protected DefaultErrorResult handleMethodArgumentNotValidException(MethodArgumentNotValidException e, HttpServletRequest request) {
        log.info("handleMethodArgumentNotValidException start, uri:{}, caused by: ", request.getRequestURI(), e);
        List<ParameterInvalidItem> parameterInvalidItemList = ParameterInvalidItemHelper.convertBindingResultToMapParameterInvalidItemList(e.getBindingResult());
        return DefaultErrorResult.failure(ResultCode.PARAM_IS_INVALID, e, HttpStatus.BAD_REQUEST, parameterInvalidItemList);
    }

    /**
     * 处理通用自定义业务异常
     */
    protected ResponseEntity<DefaultErrorResult> handleBusinessException(BusinessException e, HttpServletRequest request) {
        log.info("handleBusinessException start, uri:{}, exception:{}, caused by: {}", request.getRequestURI(), e.getClass(), e.getMessage());

        DefaultErrorResult defaultErrorResult = DefaultErrorResult.failure(e);
        return ResponseEntity
                .status(HttpStatus.valueOf(defaultErrorResult.getStatus()))
                .body(defaultErrorResult);
    }

    /**
     * 处理未预测到的其他错误（反500错误码）
     */
    protected DefaultErrorResult handleThrowable(Throwable e, HttpServletRequest request) {
        log.error("handleThrowable start, uri:{}, caused by: ", request.getRequestURI(), e);
        return DefaultErrorResult.failure(ResultCode.SYSTEM_INNER_ERROR, e, HttpStatus.INTERNAL_SERVER_ERROR);
    }

}

说明

上面用到了一些自定义异常基类（BusinessException），对于这个类它会有很多子类去继承它，例如：
参数异常、数据已存在异常、无权限异常等等，这些类大家可以根据自己的业务扩展

ResponseResult 注解类

package cn.notemi.demo.annotations;

import cn.notemi.demo.result.PlatformResult;
import cn.notemi.demo.result.Result;

import java.lang.annotation.*;

/**
 * @desc 接口返回结果增强  会通过拦截器拦截后放入标记，在WebResponseBodyHandler进行结果处理
 */
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ResponseResult {

    Class<? extends Result> value() default PlatformResult.class;

}

说明

这里我们默认 PlatformResult 使用这个类作为返回格式，所以@ResponseResult 等价于@ResponseResult(PlatformResult.class)

ResponseResultInterceptor 拦截器

package cn.notemi.demo.intercepter;

import cn.notemi.demo.annotations.ResponseResult;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Method;

/**
 * @desc 接口响应体控制拦截器
 */
public class ResponseResultInterceptor implements HandlerInterceptor {

    public static final String RESPONSE_RESULT = "RESPONSE-RESULT";

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        if (handler instanceof HandlerMethod) {
            final HandlerMethod handlerMethod = (HandlerMethod) handler;
            final Class<?> clazz = handlerMethod.getBeanType();
            final Method method = handlerMethod.getMethod();
            if (clazz.isAnnotationPresent(ResponseResult.class)) {
                request.setAttribute(RESPONSE_RESULT, clazz.getAnnotation(ResponseResult.class));
            } else if (method.isAnnotationPresent(ResponseResult.class)) {
                request.setAttribute(RESPONSE_RESULT, method.getAnnotation(ResponseResult.class));
            }
        }

        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        // nothing to do
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        // nothing to do
    }

}

开启拦截器配置

package cn.notemi.demo.config;

import cn.notemi.demo.intercepter.HeaderParamsCheckInterceptor;
import cn.notemi.demo.intercepter.LoginAuthInterceptor;
import cn.notemi.demo.intercepter.ResponseResultInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Configuration
public class InterceptorConfig extends WebMvcConfigurerAdapter {

    @Bean
    public ResponseResultInterceptor responseResultInterceptor() {
        return new ResponseResultInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //响应结果控制拦截
        registry.addInterceptor(responseResultInterceptor()).addPathPatterns("/**");
    }

}

ResponseResultHandler 响应体格式处理器

package cn.notemi.demo.handler;

import cn.notemi.demo.annotations.ResponseResult;
import cn.notemi.demo.constant.HeaderConstants;
import cn.notemi.demo.enums.ApiStyleEnum;
import cn.notemi.demo.intercepter.ResponseResultInterceptor;
import cn.notemi.demo.result.DefaultErrorResult;
import cn.notemi.demo.result.PlatformResult;
import cn.notemi.demo.result.Result;
import cn.notemi.demo.util.JsonUtil;
import cn.notemi.demo.util.RequestContextUtil;
import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

import javax.servlet.http.HttpServletRequest;

/**
 * @desc 接口响应体处理器
 */
@ControllerAdvice
public class ResponseResultHandler implements ResponseBodyAdvice<Object> {

    @Override
    public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
        HttpServletRequest request = RequestContextUtil.getRequest();
        ResponseResult responseResultAnn = (ResponseResult) request.getAttribute(ResponseResultInterceptor.RESPONSE_RESULT);
        return responseResultAnn != null && !ApiStyleEnum.NONE.name().equalsIgnoreCase(request.getHeader(HeaderConstants.API_STYLE));
    }

    @Override
    public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {
        ResponseResult responseResultAnn = (ResponseResult) RequestContextUtil.getRequest().getAttribute(ResponseResultInterceptor.RESPONSE_RESULT);

        Class<? extends Result> resultClazz = responseResultAnn.value();

        if (resultClazz.isAssignableFrom(PlatformResult.class)) {
            if (body instanceof DefaultErrorResult) {
                DefaultErrorResult defaultErrorResult = (DefaultErrorResult) body;
                return PlatformResult.builder()
                        .code(defaultErrorResult.getCode())
                        .msg(defaultErrorResult.getMessage())
                        .data(defaultErrorResult.getErrors())
                        .build();
            } else if (body instanceof String) {
                return JsonUtil.object2Json(PlatformResult.success(body));
            }

            return PlatformResult.success(body);
        }

        return body;
    }

}

说明

上述代码用到了一个工具类（RequestContextHolderUtil）用于获取request对象，如果感兴趣可以看下这篇文章 工具类分享之《RequestContextHolderUtil》

@ControllerAdvice、ResponseBodyAdvice 这两个类是本功能的关键使用类，用于接口的响应体增强，其中 supports 方法用于判断是否需要做增强转化，beforeBodyWrite 方法用于增加逻辑实现

supports 方法中，加了个小功能，当调用人员不想要封装结果时，可以在 header 上设置参数 Api-Style=none

测试

package cn.notemi.demo.controller;

import cn.notemi.demo.annotations.LoginAuth;
import cn.notemi.demo.annotations.ResponseResult;
import cn.notemi.demo.model.bo.LoginUser;
import cn.notemi.demo.model.po.User;
import cn.notemi.demo.model.qo.LoginQO;
import cn.notemi.demo.model.vo.LoginVO;
import cn.notemi.demo.repository.UserRepository;
import cn.notemi.demo.service.LoginService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.*;

import javax.validation.Valid;
import java.util.Date;
import java.util.List;
import java.util.UUID;

/**
 * Title：UserController
 **/
@RestController
@RequestMapping("/api/user")
@ResponseResult
public class UserController {

    @Autowired
    private UserRepository userRepository;

    @GetMapping("/all")
    public List<User> users() {
        return userRepository.findAll();
    }
}

结束语

接口响应体统一格式转化，这个功能就完成了，这样的封装可以少些很多重复且无用的代码，何乐而不为呢？

GitHub地址：https://github.com/FlickerMi/notemi-demo