Spring注解之@RestControllerAdvice

前言

    前段时间部门搭建新系统，需要出异常后统一接口的返回格式，于是用到了Spring的注解@RestControllerAdvice。现在把此注解的用法总结一下。

用法

    首先定义返回对象ResponseDto

package com.staff.points.common;

import lombok.Data;

import java.io.Serializable;

@Data
public class ResponseDto<T> implements Serializable {
    private static final long serialVersionUID = -284719732991678911L;

    private String code;

    private String message;

    private T data;

    public static <T> ResponseDto<T> assemblingSuccessResponse(T data) {
        ResponseDto<T> responseDto = new ResponseDto<>();
        responseDto.setCode(ResponseCodeEnum.SUCCESS.getCode());
        responseDto.setMessage(ResponseCodeEnum.SUCCESS.getMessage());
        responseDto.setData(data);
        return responseDto;
    }

    public static <T> ResponseDto<T> assemblingSuccessResponse() {
        ResponseDto<T> responseDto = new ResponseDto<>();
        responseDto.setCode(ResponseCodeEnum.SUCCESS.getCode());
        responseDto.setMessage(ResponseCodeEnum.SUCCESS.getMessage());
        responseDto.setData(null);
        return responseDto;
    }

    public static <T> ResponseDto<T> assemblingFailureResponse(ResponseCodeEnum data) {
        ResponseDto<T> responseDto = new ResponseDto<>();
        responseDto.setCode(data.FAILURE.getCode());
        responseDto.setMessage(data.FAILURE.getMessage());
        return responseDto;
    }

    public static <T> ResponseDto<T> assemblingFailureResponse() {
        ResponseDto<T> responseDto = new ResponseDto<>();
        responseDto.setCode(ResponseCodeEnum.FAILURE.getCode());
        responseDto.setMessage(ResponseCodeEnum.FAILURE.getMessage());
        return responseDto;
    }
}

    然后定义返回码的枚举类，此处只定义了两种，有需要可以往下添加很多。

package com.staff.points.common;

import lombok.AllArgsConstructor;
import lombok.Getter;

@AllArgsConstructor
@Getter
public enum ResponseCodeEnum {
    SUCCESS("00", "成功"),
    FAILURE("01", "系统异常");


    private String code;
    private String message;
}

    下面是自定义的异常类

package com.staff.points.common;

import lombok.Data;

@Data
public class StaffPointsException extends RuntimeException{
    private String code;
    private String message;
    public StaffPointsException () {}

    public StaffPointsException (Exception e) {
        super(e);
    }

    public StaffPointsException (String code, String message) {
        super(message);
        this.code = code;
        this.message = message;
    }

    public StaffPointsException (ResponseCodeEnum codeEnum) {
        super(codeEnum.getMessage());
        this.code = codeEnum.getCode();
        this.message = codeEnum.getMessage();
    }
}

    然后是关键的@RestControllerAdvice修饰的类

package com.staff.points.exception;

import com.staff.points.common.ResponseCodeEnum;
import com.staff.points.common.ResponseDto;
import com.staff.points.common.StaffPointsException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

@RestControllerAdvice
@Component
public class UnifyExceptionHandler {
    private Logger logger = LoggerFactory.getLogger(UnifyExceptionHandler.class);

    @ExceptionHandler(Exception.class)
    public ResponseDto handlerCommonException (Exception e) {
        ResponseDto responseDto = new ResponseDto<>();
        responseDto.setCode(ResponseCodeEnum.FAILURE.getCode());
        responseDto.setMessage(ResponseCodeEnum.FAILURE.getMessage());
        logger.info("UnifyExceptionHandler.handlerCommonException exception:" + e);
        return responseDto;
    }
    // 报StaffPointException时，对其进行拦截并处理的方法
    @ExceptionHandler(StaffPointsException.class)
    public ResponseDto handlerCustomizeException (StaffPointsException e) {
        ResponseDto responseDto = new ResponseDto<>();
        responseDto.setCode(e.getCode());
        responseDto.setMessage(e.getMessage());
        logger.info("UnifyExceptionHandler.handlerCustomizeException StaffPointsException:" + e);
        return responseDto;
    }
}

    运行代码时，如果出现了StaffPointException，那么就会被拦截进入第27行的方法（就是说可以自由的在业务代码里往外throw自定义异常了）；如果出现了其他的异常，则进入18行的方法，统一返回。

验证一下，在代码里造一个NPE异常时，返回结果：

{
  "code": "01",
  "message": "系统异常",
  "data": null
}

    造一个StaffPointsException异常时，返回结果：

{
  "code": "99",
  "message": "自定义业务异常",
  "data": null
}

    它的作用原理，大体是先在spring初始化时将类扫描进容器，出异常后，在DispatcherServlet类的doDispatch方法中调用了对异常的拦截处理。

小结

    看@RestControllerAdvice源码可以知道，它就是@ControllerAdvice和@ResponseBody的合并。此注解通过对异常的拦截实现的统一异常返回处理，如果大家在项目中有类似的需求，不妨试一下，好用又方便。