Spring的基础

统一异常处理

如果在业务逻辑中出现异常，通常是在最外层的Controller中进行try catch捕获处理，但是这样每一个controller都需要进行try catch，而Spring提供了全局统一异常处理的方式处理拦截Controller中暴露的异常错误。

@RestControllerAdvice
public class GlobalExceptionHandler {
    
  @ExceptionHandler(Exception.class)
    public ResultWrapper globalException() {
        return new ResultWrapper("全局错误码","全局异常");
    }
    
    @ExceptionHandler(NullPointerException.class)
    public ResultWrapper customException(HttpServletResponse response,NullPointerException ex){
    //从异常中获取
        return new ResultWrapper("错误码","错误信息");
    }
}

参数校验

@Data
@Builder
public class ResultWrapper<T>{
  private String code;
    private String message;
    private T data;
}

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
</dependency>

@Data
public class LoginDTO {
  @NotNull(message = "用户名不能为空")
  private String userName;
  
  @NotBlank(message = "密码不能为空")
  @Length(min = 6, message = "密码长度至少6位")
  private String password;
  
  @Email
  private String email;
}

@RestController
public class LoginController {
  @PostMapping("/login")
  public ResultWrapper login(@RequestBody @Valid LoginDTO loginDTO) {
    //登录逻辑
        return ResultWrapper();
  }
}

但是这样会直接将返回的message返回到前端，而不是我们定义的BaseResult返回格式，需要再进行一层结果集包装。

@RestControllerAdvice
public class GlobalExceptionAdvice {


    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResultWrapper methodArgumentNotValidException(MethodArgumentNotValidException e) {
        List<ObjectError> errors = e.getBindingResult().getAllErrors();
        // 已经设置了快速失败，可以默认取首个错误即可
        StringBuffer sb = new StringBuffer();
        List<String> errorArr = Lists.newArrayList();
        for (ObjectError error : errors) {
            if (error instanceof FieldError) {
                FieldError fieldError = (FieldError) error;
                errorArr.add(fieldError.getField() + fieldError.getDefaultMessage());
            } else {
                errorArr.add(error.getObjectName() + error.getDefaultMessage());
            }
        }
        String errMsg = String.join(";", errorArr.toArray(new String[]{}));
        return new ResultWrapper("错误码xxx", errMsg);
    }
}

全局异常处理类

@ControllerAdvice
public class GlobalExceptionAdvice {

    //自定义异常
    @ResponseBody
    @ExceptionHandler({BusinessException.class})
    public ResultWrapper bizException(BusinessException e) {
        log.error("出现异常:{}", e);
        return ResultWrapper.builder().code(e.getErrorCode()).msg(e.getMessage()).build();
    }

    //参数异常
    @ResponseBody
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResultWrapper methodArgumentNotValidException(MethodArgumentNotValidException e) {
        log.error("出现异常:{}", e);
        List<ObjectError> errors = e.getBindingResult().getAllErrors();
        // 已经设置了快速失败，可以默认取首个错误即可
        StringBuffer sb = new StringBuffer();
        List<String> errorArr = Lists.newArrayList();
        for (ObjectError error : errors) {
            if (error instanceof FieldError) {
                FieldError fieldError = (FieldError) error;
                errorArr.add(fieldError.getField() + fieldError.getDefaultMessage());
            } else {
                errorArr.add(error.getObjectName() + error.getDefaultMessage());
            }
        }
        String errMsg = String.join(";", errorArr.toArray(new String[]{}));
        return ResultWrapper.builder().code(StateCodeEnum.METHOD_ARGUMENT_NOT_VALID.getCode()).msg(errMsg).build();
    }

    @ResponseBody
    @ExceptionHandler(ConstraintViolationException.class)
    public ResultWrapper constraintViolationException(ConstraintViolationException e) {
        // 拦截单个参数校验异常捕获
        log.error("出现异常:{}", e);
        // @RequestParam 参数校验失败
        StringBuffer sb = new StringBuffer();
        List<String> errorArr = Lists.newArrayList();
        for (ConstraintViolation constraint : e.getConstraintViolations()) {
            errorArr.add(constraint.getInvalidValue() + "非法" + constraint.getMessage());
        }
        String errMsg = String.join(";", errorArr.toArray(new String[]{}));
        return ResultWrapper.builder().code(StateCodeEnum.CONSTRAINT_VIOLATION.getCode()).msg(errMsg).build();
    }

    //全局异常
    @ResponseBody
    @ExceptionHandler(Exception.class)
    public ResultWrapper exception(Exception e) {
        log.error("出现异常:{}", e);
        return ResultWrapper.builder().code(StateCodeEnum.ERROR.getCode()).msg(e.getMessage()).build();
    }


    /**
     * 参数错误类型转换异常
     *
     * @param e
     * @return
     */
    @ResponseBody
    @ExceptionHandler(HttpMessageConversionException.class)
    public ResultWrapper parameterTypeConvertException(HttpMessageConversionException e) {
        return ResultWrapper.builder().code(StateCodeEnum.ERROR.getCode()).msg(e.getMessage()).build();
    }
}