成功拦截：

会出现下边两个问题：

1、异常不被统一处理

2、处理成功的情况下，返回结果会报错

上面两个问题如何解决呢？

@WebFilter注解方式配置的过滤器

package com.imooc.mall.filter;

import com.imooc.mall.common.ApiRestResponse;
import com.imooc.mall.common.Constant;
import com.imooc.mall.exception.ImoocMallException;
import com.imooc.mall.exception.ImoocMallExceptionEnum;
import com.imooc.mall.model.pojo.User;
import com.imooc.mall.service.UserService;

import javax.annotation.Resource;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;
@WebFilter(filterName = "adminFilter" , urlPatterns = {"/admin/category/*","/admin/product/*","/admin/order/*"})
public class AdminFilter implements Filter {
    @Resource
    private UserService userService;
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        Filter.super.init(filterConfig);
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletResponse.reset();
        servletResponse.setContentType("text/json;charset=utf-8");
        HttpSession session = ((HttpServletRequest)servletRequest).getSession();
        User currentUser = (User) session.getAttribute(Constant.IMOOC_MALL_USER);
        PrintWriter out = servletResponse.getWriter();
        if (currentUser == null){
            out.write("{\n" +
                    "    \"code\": 10007,\n" +
                    "    \"msg\": \"用户未登录\",\n" +
                    "    \"data\": null\n" +
                    "}");
            return;
        }
        if (userService.checkAdminRole(currentUser)) {
            filterChain.doFilter(servletRequest, servletResponse);
        }else {
            out.write("{\n" +
                    "    \"code\": 10009,\n" +
                    "    \"msg\": \"无管理员权限\",\n" +
                    "    \"data\": null\n" +
                    "}");
        }
        out.flush();
        out.close();
    }

    @Override
    public void destroy() {
        Filter.super.destroy();
    }
}