自定义过滤器

首先在web.xml中对过滤器的监听

<!-- 自定义过滤器 -->
  <filter>
      <filter-name>AscFilter</filter-name>
      <filter-class>com.llh.filter.AscFilter</filter-class>
  </filter>
  <filter-mapping>
      <filter-name>AscFilter</filter-name>
      <url-pattern>/main.jsp</url-pattern>
  </filter-mapping>
  

新建一个包com.llh.filter,创建一个实现Filter接口的类

package com.llh.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.llh.entity.Student;

/**
 * 过滤登陆
 * 
 * @author Administrator
 *
 */
public class AscFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // TODO Auto-generated method stub
    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
            throws IOException, ServletException {
        // TODO Auto-generated method stub
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        Student s = (Student) request.getSession().getAttribute("s");
        System.out.println("lanj");
        if(s==null){
            System.out.println("拦截了");
            response.sendRedirect("login.jsp");
        }
        chain.doFilter(request, response);
    }
    
    @Override
    public void destroy() {
        // TODO Auto-generated method stub
    }

}

过滤所有界面的编码