Filter的使用-优快云博客

本文介绍了一个基于Java的登录过滤器(LoginFilter)实现方法，该过滤器用于检查用户的会话状态，若未登录则重定向至登录页面。适用于保护网站的部分页面免受未授权访问。

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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>