Spring boot @ExceptionHandler 自定义异常拦截，并确认该返回视图还是json

package cn.com.cmbc.e.controller;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

import cn.com.cmbc.e.model.ReturnCode;

@ControllerAdvice
public class ExceptionController {
	
	@Autowired
	private HttpServletRequest request;    
	@Autowired
	private HttpServletResponse response;
	
	@ExceptionHandler(Exception.class)
	@ResponseBody
	public ReturnCode handleException(Exception e) {
		LoggerFactory.getLogger(this.getClass()).error("【异常拦截日志】>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>", e);
		try {
			if (request.getHeader("accept").indexOf("text/html") != -1) {  //如果接受类型为html，就返回错误页面，否则返回json文本
				request.setAttribute("msg", e.getMessage());
				//必须使用注入的request和response，不能在方法参数中定义request和response，否则不会拦截org.springframework.web.bind.MissingServletRequestParameterException等异常
				request.getRequestDispatcher("/WEB-INF/view/error.jsp").forward(request, response); 
				return null;
			}
		} catch (ServletException | IOException ex) {
			LoggerFactory.getLogger(this.getClass()).error("handleException发生了异常", ex);
		}
		return ReturnCode.fail(e.getMessage());  //ReturnCode是用来返回统一json格式的javaBean
	}
}

@RequestMapping("login")
    public String index(@RequestParam String username) {
        return "index";
    }

如果username没有传值，这时候就会引发org.springframework.web.bind.MissingServletRequestParameterException