SpringBoot 处理异常的几种方法

1. 使用 @ControllerAdvice 和 @ExceptionHandler 处理全局异常

①新建异常实体类

public class ErrorResponse {
    private String message;
    private String errorTypeName;

    public ErrorResponse(Exception e) {
        this(e.getClass().getName(), e.getMessage());
    }

    public ErrorResponse(String errorTypeName, String message) {
        this.errorTypeName = errorTypeName;
        this.message = message;
    }
    ......省略getter/setter方法
}

②自定义异常类型
一般我们处理的都是 RuntimeException ，所以如果你需要自定义异常类型的话直接集成这个类就可以了。

public class ResourceNotFoundException extends RuntimeException {
    private String message;

    public ResourceNotFoundException() {
        super();
    }

    public ResourceNotFoundException(String message) {
        super(message);
        this.message = message;
    }

    @Override
    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

③新建异常处理类
我们只需要在类上加上@ControllerAdvice注解这个类就成为了全局异常处理类，当然你也可以通过 assignableTypes指定特定的 Controller 类，让异常处理类只处理特定类抛出的异常。

@ControllerAdvice(assignableTypes = {ExceptionController.class})
@ResponseBody
public class GlobalExceptionHandler {

    ErrorResponse illegalArgumentResponse = new ErrorResponse(new IllegalArgumentException("参数错误!"));
    ErrorResponse resourseNotFoundResponse = new ErrorResponse(new ResourceNotFoundException("Sorry, the resourse not found!"));

    @ExceptionHandler(value = Exception.class)// 拦截所有异常, 这里只是为了演示，一般情况下一个方法特定处理一种异常
    public ResponseEntity<ErrorResponse> exceptionHandler(Exception e) {

        if (e instanceof IllegalArgumentException) {
            return ResponseEntity.status(400).body(illegalArgumentResponse);
        } else if (e instanceof ResourceNotFoundException) {
            return ResponseEntity.status(404).body(resourseNotFoundResponse);
        }
        return null;
    }
}

ResponseEntity 可以定义返回的HttpStatus（状态码）和HttpHeaders（消息头：请求头和响应头)。

ResponseEntity的优先级高于@ResponseBody。
在不是ResponseEntity的情况下才去检查有没有@ResponseBody注解。如果响应类型是ResponseEntity可以不写@ResponseBody注解，写了也没有关系。

简单的说
@ResponseBody可以直接返回Json结果，
@ResponseEntity不仅可以返回json结果，还可以定义返回的HttpHeaders和HttpStatus。

④controller模拟抛出异常

@RestController
@RequestMapping("/api")
public class ExceptionController {

    @GetMapping("/illegalArgumentException")
    public void throwException() {
        throw new IllegalArgumentException();
    }

    @GetMapping("/resourceNotFoundException")
    public void throwException2() {
        throw new ResourceNotFoundException();
    }
}

2.@ExceptionHandler 处理 Controller 级别的异常(使用的比较少)

 @ExceptionHandler(value = Exception.class)// 拦截所有异常
    public ResponseEntity<ErrorResponse> exceptionHandler(Exception e) {

        if (e instanceof IllegalArgumentException) {
            return ResponseEntity.status(400).body(illegalArgumentResponse);
        } else if (e instanceof ResourceNotFoundException) {
            return ResponseEntity.status(404).body(resourseNotFoundResponse);
        }
        return null;
    }

3.ResponseStatusException

通过 ResponseStatus注解简单处理异常的方法（将异常映射为状态码）。

ResponseStatusException 提供了三个构造方法：

public ResponseStatusException(HttpStatus status) {
        this(status, null, null);
    }

    public ResponseStatusException(HttpStatus status, @Nullable String reason) {
        this(status, reason, null);
    }

    public ResponseStatusException(HttpStatus status, @Nullable String reason, @Nullable Throwable cause) {
        super(null, cause);
        Assert.notNull(status, "HttpStatus is required");
        this.status = status;
        this.reason = reason;
    }

@GetMapping("/resourceNotFoundException2")
    public void throwException3() {
        throw new ResponseStatusException(HttpStatus.NOT_FOUND, "Sorry, the resourse not found!", new ResourceNotFoundException());
    }

4.实现WebMvcConfigurer 接口，增加异常处理器

import com.alibaba.fastjson.JSON;
import com.scaffold.test.base.Result;
import com.scaffold.test.base.ResultCode;
import com.scaffold.test.base.ServiceException;
import com.scaffold.test.config.interceptor.AuthenticationInterceptor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.validation.BindingResult;
import org.springframework.validation.ObjectError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

/**
 * @author alex
 */

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    private final Logger logger = LoggerFactory.getLogger(WebMvcConfigurer.class);

    /**
     * 统一异常处理
     *
     * @param exceptionResolvers
     */
    @Override
    public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {
        exceptionResolvers.add((request, response, handler, e) -> {
            Result result = new Result();
            // 异常处理
            // 参数异常判断
            if (e instanceof BindingResult || e instanceof MethodArgumentNotValidException) {
                StringBuilder errorMessage = new StringBuilder();
                List<ObjectError> allErrors;
                if (e instanceof BindingResult) {
                    allErrors = ((BindingResult) e).getAllErrors();
                } else {
                    BindingResult bindingResult = ((MethodArgumentNotValidException) e).getBindingResult();
                    allErrors = bindingResult.getAllErrors();
                }
                for (int i = 0; i < allErrors.size(); i++) {
                    errorMessage.append(allErrors.get(i).getDefaultMessage());
                    if (i != allErrors.size() - 1) {
                        errorMessage.append(",");
                    }
                }
                result.setCode(ResultCode.FAIL).setMessage(errorMessage.toString());
                logger.error(errorMessage.toString());
            } else if (e instanceof ServiceException) {
                // 1、业务失败的异常，如“账号或密码错误”
                result.setCode(ResultCode.FAIL).setMessage(e.getMessage());
                logger.info(e.getMessage());
            } else if (e instanceof ServletException) {
                // 2、调用失败
                result.setCode(ResultCode.FAIL).setMessage(e.getMessage());
            } else {
                // 3、内部其他错误
                result.setCode(ResultCode.INTERNAL_SERVER_ERROR).setMessage("接口 [" + request.getRequestURI() + "] 内部错误，请联系管理员");
                String message;
                if (handler instanceof HandlerMethod) {
                    HandlerMethod handlerMethod = (HandlerMethod) handler;
                    message = String.format("接口 [%s] 出现异常，方法：%s.%s，异常摘要：%s",
                            request.getRequestURI(),
                            handlerMethod.getBean().getClass().getName(),
                            handlerMethod.getMethod().getName(),
                            e.getMessage());
                } else {
                    message = e.getMessage();
                }
                result.setMessage(message);
                logger.error(message, e);
            }
            responseResult(response, result);
            return new ModelAndView();
        });
    }

    // 处理响应数据格式
    private void responseResult(HttpServletResponse response, Result result) {
        response.setCharacterEncoding("UTF-8");
        response.setHeader("Content-type", "application/json;charset=UTF-8");
        response.setStatus(200);
        try {
            response.getWriter().write(JSON.toJSONString(result));
        } catch (IOException ex) {
            logger.error(ex.getMessage());
        }
    }

}