1.介绍ExceptionHandler与ControllerAdvice

@ExceptionHandler
注解到方法上，出现异常时会执行该方法。
@ControllerAdvice
使一个Contoller成为全局的异常处理类，类中用@ExceptionHandler方法注解的方法可以处理所有Controller发生的异常。

1.处理局部异常（Controller内）

    @ExceptionHandler
    public ModelAndView exceptionHandler(Exception ex){
        ModelAndView mv = new ModelAndView("error");
        mv.addObject("exception", ex);
        return mv;
    }

2.处理全局异常（所有Controller）

@ControllerAdvice
public class testControllerAdvice {
    @ExceptionHandler
    public ModelAndView exceptionHandler(Exception ex){
        ModelAndView mv = new ModelAndView("error");
        mv.addObject("exception", ex);
        return mv;
    }
}

2.定义统一的返回体

现在基本都是前后端分离，后端只需要提供json接口。需要定制个通用返回体。

{
        "msg": "操作成功",
        "success": true,
        "result":{
          },
        "code": 1
}

真正需要返回的数据在result里面。普通Controller返回的内容会被放在result里面。这样业务中不需要去考虑response,只需要返回数据，和抛出异常就行了。

@ControllerAdvice(basePackages = "com.xiong")
public class ResultResponseBodyAdvice implements ResponseBodyAdvice<Object>{

    private final static int successCode=1;//成功编码
    private final static int errorCode=0;//验证错误 (定义一个验证异常，验证失败抛异常，比如参数错误，主要验证前端参数)
    private final static int sysErrorCode=-1;//系统错误
    private final static String DefaultMsg="网络不给力，请稍后再试";


    @Override
    /**
     * 过滤是否是json的数据
     */

    public boolean supports(MethodParameter methodParameter, Class aClass) {

        Boolean isRest = AnnotationUtils.isAnnotationDeclaredLocally(
                RestController.class, methodParameter.getContainingClass());
        ResponseBody responseBody = AnnotationUtils.findAnnotation(
                methodParameter.getMethod(), ResponseBody.class); //得到方法上的注解
        if (isRest || responseBody != null) {
            return true;
        } else {
            return false;
        }

    }

    /**
     * 修改返回的数据
     */
    @Override
    public Object beforeBodyWrite(Object o, MethodParameter methodParameter, MediaType mediaType, Class aClass, ServerHttpRequest serverHttpRequest, ServerHttpResponse serverHttpResponse) {
        if (o instanceof Result) {
            return o;
        }
        Result result = Result.getInstance();
        o = o==null?"":o;
        result.setResult(o);
        return result;

    }



    /**
     * 全局异常的处理
     * @param request
     * @param ex
     * @return
     */
    @ExceptionHandler(value = {Exception.class})
    @ResponseBody
    public Result handleAllException(HttpServletRequest request, Exception ex) {

        ex.printStackTrace();
        String msg = DefaultMsg;
        Integer code = errorCode;
        if (ex instanceof ValidationException) {
            ValidationException validationException = (ValidationException)ex;
            if (validationException.getCode() != null) {
                code = validationException.getCode();
            }
            if (!StringUtils.isNullOrEmpty(validationException.getMessage())) {
                msg = validationException.getMessage();
            }
        }
        Result response = new Result();
        response.setSuccess(false);
        response.setResult("");
        response.setCode(code);
        response.setMsg(msg);
        return response;

    }


    public static class Result {
        private String msg;
        private Boolean success;
        private Object result;
        private Integer code;

        public String getMsg() {
            return msg;
        }

        public Boolean getSuccess() {
            return success;
        }

        public Object getResult() {
            return result;
        }

        public Integer getCode() {
            return code;
        }

        public void setMsg(String msg) {
            this.msg = msg;
        }

        public void setSuccess(Boolean success) {
            this.success = success;
        }

        public void setResult(Object result) {
            this.result = result;
        }

        public void setCode(Integer code) {
            this.code = code;
        }

        public static Result getInstance() {
            Result result = new Result();
            result.setSuccess(true);
            result.setMsg("操作成功");
            result.setResult("");
            result.setCode(successCode);
            return result;
        }
    }
}