Filter的使用

LoginFilter.java

 

package com.yimei.drp.filter;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

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 javax.servlet.http.HttpSession;

public class LoginFilter implements Filter {
    protected FilterConfig filterConfig = null;
    private String sessionKey = null;

    public void doFilter(ServletRequest servletRequest,
            ServletResponse servletResponse, FilterChain filterChain)
            throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        HttpSession session = request.getSession();
        Long  UserID =(Long)session.getAttribute("UserID");

        System.out.println("login UserID:"+UserID);

        if (UserID==null||"null".equals(UserID)||"".equals(UserID)||UserID==0) {
            response.sendRedirect("../login.jsp");
            return;
        }

        filterChain.doFilter(request, response);
    }

    public void destroy() {
    }



    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
    }
}

 

web.xml中的配置

 

  <filter>
    <filter-name>LoginFilter</filter-name>
    <filter-class>com.yimei.drp.filter.LoginFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>LoginFilter</filter-name>
    <url-pattern>/pages/*</url-pattern>
  </filter-mapping>