统一异常处理

当用spring boot开发后端时，我们常采用前后端分离的开发策略，这时候要求前端与后端需要进行数据交互，传统的一般采用json数据交互。

这时候我们要对spring boot的默认异常处理方式进行修改了，要统一返回数据格式，优雅的数据交互，优雅的开发应用。

首先我们要了解一般springboot的错误发生在什么地方。

一般发生在controller、业务层、filter中（如spring security）、拦截器中、还有就是未知错误了。

下面我分享一下我的处理方式: @RestControllerAdvice+filter+重写BasicErrorController的处理方式。

@RestControllerAdvice

@RestControllerAdvice+@ExceptionHandler(Exception.class)可以处理经过controller的异常错误

@RestControllerAdvice
public class BaseExceptionHandler {
    private static final Logger logger = LoggerFactory.getLogger(BaseExceptionHandler.class);

    /**
     * 未知异常
     * @param e 异常
     * @return 统一结果返回
     */
    @ExceptionHandler(Exception.class)
    public R exception(Exception e) {
        logger.error(e.getMessage(), e);
        return R.error().message(e.getMessage());
    }
    @ExceptionHandler(NoHandlerFoundException.class)
    public R noHandlerFoundException(){
        return R.error().message("当前页面不存在");
    }
}
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filter捕获所有异常

当错误没有经过controller时，@RestControllerAdvice是不能捕获的，这时候就需要在filter进行处理。

public class ExceptionHandlerFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain){
        try {
            filterChain.doFilter(servletRequest, servletResponse);
        } catch (Exception e) {
            ResponseUtils.out((HttpServletResponse) servletResponse, R.error().message(e.getMessage()));
        }
    }
}
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记得filter一定要注册到springboot才有作用，下面是我喜欢的一种方式

@Bean
FilterRegistrationBean<ExceptionHandlerFilter> exceptionFilterRegistrationBean() {
    FilterRegistrationBean<ExceptionHandlerFilter> bean = new FilterRegistrationBean<>();
    bean.setFilter(new ExceptionHandlerFilter());
    bean.setOrder(Ordered.HIGHEST_PRECEDENCE);//放在最前面
    return bean;
}
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未知异常处理

当发生的异常不知道在哪时，springboot会进行默认异常处理，跳转到 /error

这时我们要统一数据返回就必须要从这下手了，创建一个新的Controller处理/error，继承BasicErrorController，并覆盖其中的方法

@RestController
public class MyErrorController extends BasicErrorController {

    @Autowired
    public MyErrorController(ErrorAttributes errorAttributes,
                             ServerProperties serverProperties,
                             List<ErrorViewResolver> errorViewResolvers) {
        super(errorAttributes, serverProperties.getError(), errorViewResolvers);
    }


    @Override
    public ModelAndView errorHtml(HttpServletRequest request,
                                  HttpServletResponse response) {
        HttpStatus status = getStatus(request);
        Map<String, Object> model = Collections
                .unmodifiableMap(getErrorAttributes(request, getErrorAttributeOptions(request, MediaType.TEXT_HTML)));
//        return new ModelAndView("error", model, status);
        ResponseUtils.out(response, R.error().code(status.value()).message((String) model.get("error")));
        return null;
    }

    @Override
    public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) {
        Map<String, Object> body = getErrorAttributes(request, getErrorAttributeOptions(request, MediaType.ALL));

        //可以换成项目中自定义的通信json
        Map<String, Object> resultBody = new HashMap<>(16);
        resultBody.put("success", false);
        resultBody.put("code", body.get("status"));
        resultBody.put("message", body.get("error"));
        Map<String, Object> data = new HashMap<>();
        data.put("timestamp", body.get("timestamp"));
        data.put("path", body.get("path"));
        resultBody.put("data", data);
        return new ResponseEntity<>(resultBody, HttpStatus.OK);
    }
}
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配置文件

spring:
  mvc:
    throw-exception-if-no-handler-found: true
  web:
    resources:
      add-mappings: false
server:
  error:
    include-exception: true
  servlet:
    encoding:
      charset: utf-8
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统一结果返回的工具类

ResponseUtils

public class ResponseUtils {
    public static void out(HttpServletResponse response, R r) {
        ObjectMapper mapper = new ObjectMapper();
        response.setStatus(HttpStatus.OK.value());
        response.setContentType("application/json;charset=UTF-8");
        try {
            mapper.writeValue(response.getWriter(), r);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
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R

@Data
public class R implements Serializable {
    private boolean success;

    private Integer code;
    private String message;
    private Map data;
    private R(){}
    public static R ok(){
        R r = new R();
        r.setSuccess(true);
        r.setCode(200);
        r.setMessage("成功");
        r.setData(new HashMap<>());
        return r;
    }
    public static R error() {
        R r = new R();
        r.setSuccess(false);
        r.setCode(500);
        r.setMessage("失败");
        r.setData(new HashMap<>());
        return r;
    }


    public R success(Boolean success){
        this.success = success;
        return this;
    }
    public R code(Integer code){
        this.code = code;
        return this;
    }
    public R message(String message){
        this.message = message;
        return this;
    }

    public R data(String key, Object value){
        this.data.put(key,value);
        return this;
    }
    public R data(Map map){
        this.setData(map);
        return this;
    }

}
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