java拦截器（访问过滤器）Filter

web.xml 页面配置

（ps:本来是想在init-param里配置静态资源不拦截，结果没生效，于是便改成了只拦截jsp文件，

      拦截参数可以同时过滤多种类型资源，如下同时拦截jsp和html文件）

    

    <filter>
        <filter-name>LoginFilterfilter-name>
        <filter-class>com.sdcit.filter.Filterfilter-class>
        
            
            
        
    filter>
    <filter-mapping>
        <filter-name>LoginFilterfilter-name>
        <url-pattern>*.jspurl-pattern>
        
        

    filter-mapping> 
    
	<filter-mapping>
        <filter-name>LoginFilterfilter-name>
        <url-pattern>*.htmlfilter-mapping>
    

Filter类项目摘录；

package com.sdcit.filter;

import com.sdcit.bean.User;
import com.sdcit.service.AuthorityService;
import com.sdcit.service.UserService;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

//@WebFilter(filterName = "Filter")
public class Filter implements javax.servlet.Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws ServletException, IOException {
//        chain.doFilter(req, resp);
        servletRequest.setCharacterEncoding("utf-8");
        servletResponse.setCharacterEncoding("utf-8");
        HttpServletRequest requ = (HttpServletRequest) servletRequest;
        HttpServletResponse res = (HttpServletResponse) servletResponse;
        requ.setCharacterEncoding("utf-8");
        res.setCharacterEncoding("utf-8");
        HttpSession session = requ.getSession(true);

        User user = (User) session.getAttribute("user");
        String url = requ.getRequestURI();
        System.out.println("请求的url-->>" + url);
        if(url.equals("/login.jsp") || url.equals("/LoginServlet") || url.equals("/")){//登陆页，不拦截
            System.out.println("登陆页，不拦截");
            filterChain.doFilter(servletRequest, servletResponse); //FilterChain 接口的 doFilter 方法用于通知 Web 容器把请求交给 Filter 链中的下一个 Filter 去处理，如果当前调用此方法的 Filter 对象是Filter 链中的最后一个 Filter，那么将把请求交给目标 Servlet 程序去处理。
        }else if(user != null) {
            System.out.println("用户请求页");
            if(session.getAttribute("authList") == null) {
                System.out.println("获取权限数据。。。");
                UserService userService = new UserService();
                int roleId = userService.getRoleIdByUserId(user.getUserId());//通过userId获取roleId角色
                AuthorityService authorityService = new AuthorityService();
                List<String> authList = authorityService.getAuthoritiesByRoleId(roleId);
                
//                List authList = new ArrayList();//模拟数据测试
//                authList.add("1");
//                authList.add("3");
//                authList.add("6");
                requ.setAttribute("authList",authList);
            }
            filterChain.doFilter(servletRequest, servletResponse); //FilterChain 接口的 doFilter 方法用于通知 Web 容器把请求交给 Filter 链中的下一个 Filter 去处理，如果当前调用此方法的 Filter 对象是Filter 链中的最后一个 Filter，那么将把请求交给目标 Servlet 程序去处理。
        }else{
            System.out.println("未登录,转向login.jsp");
            res.sendRedirect(requ.getContextPath()+"/login.jsp");
        }
    }

    public void init(FilterConfig config) throws ServletException {

    }

}