JavaWeb-过滤器Filter学习(三)实现用户的自动登录与IP黑名单过滤

实现用户的自动登录：
解决方案：
设置一个全站拦截的过虑器。
在此过虑器中，读取用户带过来的Cookie信息，然后从中读取用户的用户名和密码，自动帮助用户登录。
即可实现自动登录功能。

用Filter验证用户是否已经登录过。已经登录过了，我们就根据他选择的自动登录来选择让他在多久内能自动登录。

IP黑名单过滤就很简单了，只要在Filter过滤器防范一下就OK。
在init方法中，我们先把黑名单的IP加载进Set<String> set集合，
Set集合有如下特点:

Java.util.HashSet类实现了Java.util.Set接口。
1 它不允许出现重复元素；
2 不保证和政集合中元素的顺序
3 允许包含值为null的元素，但最多只能有一个null元素。

contains方法:

当且仅当 本set包含一个元素 e，并且满足(o==null ? e==null : o.equals(e))条件时,contains()方法才返回true. 

因此 contains()方法 必定使用equals方法来检查是否相等.

需要注意的是: set 中是可以包含 null值的(常见的集合类都可以包含null值). 
所以如果添加了null,然后判断是否包含null,将会返回true

黑名单IP过滤:

package cn.hncu.pubs;

import java.io.IOException;
import java.util.HashSet;
import java.util.Set;

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;

public class CharacterFilter implements Filter{
private String charset;
//黑名单
private Set<String> set = new HashSet<String>();

@Override
public void init(FilterConfig filterConfig) throws ServletException {
        charset = filterConfig.getInitParameter("charset");

//到数据库中把黑名单加载进来，这里简单模拟一下
        set.add("192.168.31.168");
    }

@Override
public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        request.setCharacterEncoding(charset);

//以下演示黑名单过滤技术
        String ip = request.getRemoteAddr();;//获得客户端的IP
if(set.contains(ip)){
            HttpServletResponse resp = (HttpServletResponse) response;
            resp.setContentType("text/html;charset=utf-8");
            resp.getWriter().println("你已被列入黑名单!");
        }else{//放行
            chain.doFilter(request, response);
        }
    }

@Override
public void destroy() {
    }

}

配置web.xml：

<filter>
    <filter-name>character</filter-name>
    <filter-class>cn.hncu.pubs.CharacterFilter</filter-class>
    <init-param>
        <param-name>charset</param-name>
        <param-value>utf-8</param-value>    
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>character</filter-name>
    <url-pattern>/*</url-pattern>
 </filter-mapping>

这样就可以防止IP在黑名单的用户访问我们的网站了！

用户的自动登录

User值对象:

package cn.hncu.domain;

/**
 * @author 陈浩翔
 *
 * 2016-8-18
 */
public class User {
private String name;
private String pwd;
public User() {
super();
    }
public String getName() {
return name;
    }
public void setName(String name) {
this.name = name;
    }
public String getPwd() {
return pwd;
    }
public void setPwd(String pwd) {
this.pwd = pwd;
    }
}

LoginServlet.java：

package cn.hncu.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.hncu.domain.User;

public class LoginServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //从页面接收登录信息
        String name = request.getParameter("name");
        String pwd = request.getParameter("pwd");
        String time = request.getParameter("time");

        //System.out.println(name+","+pwd+","+time);

        User user = new User();
        user.setName(name);
        user.setPwd(pwd);

        if(name!=null && name.trim().length()!=0 && pwd!=null){
            if(name.equals(pwd)){//按理应该到后台去验证登录是否成功，这里直接以用户名和密码相同为登录成功
                request.getSession().setAttribute("user", user);
                //登录成功，就往客户端写一个cookie,将用户名和密码存到cookie中-应该进行加密!
                //为了能够兼容中文，要进行编码
                name = URLEncoder.encode(name, "utf-8");
                pwd = URLEncoder.encode(pwd, "utf-8");

                Cookie cookie = new Cookie("autoLogin", name+"#!#"+pwd);
                cookie.setPath(request.getContextPath());//权限：本项目中的类都可以访问该cookie
                //有效期
                cookie.setMaxAge( 60 * Integer.parseInt(time) );
                response.addCookie(cookie);//存储到客户端
            }else{
                request.getSession().setAttribute("error", "密码错误!");
            }
        }else{
            request.getSession().setAttribute("error", "请输入用户名!");
        }
        response.sendRedirect(request.getContextPath()+"/index.jsp");
    }

}

index.jsp:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>演示利用Filter实现自动登录</title>
</head>

<body>
<h2>主页-演示利用Filter实现自动登录</h2>
<c:if test="${!empty sessionScope.error}">
<font color="red">${sessionScope.error}</font>
<c:remove var="error" scope="session"/>
</c:if>

<c:if test="${empty sessionScope.user}" var="boo">
<form action="<c:url value='/LoginServlet'/>" method="post">
            Name:<input type="text" name="name"><br/><br/>
<!-- 这里为了演示清楚，就直接用text了 -->
            &nbsp;Pwd:<input type="text" name="pwd"><br/>
<fieldset>
<legend>自动登录</legend>
<input type="radio" name="time" value="0" checked="checked">不自动登录<br/>
<input type="radio" name="time" value="1" >1分钟<br/>
<input type="radio" name="time" value="60" >1小时<br/>
<input type="radio" name="time" value="86400" >1天<br/>
<input type="radio" name="time" value="604800" >1周<br/>
<input type="radio" name="time" value="2592000" >一个月<br/>
</fieldset>
<input type="submit" value="登录">
</form>         
</c:if>
<c:if test="${!boo}">
        ${user.name},欢迎回来。
<a href="<c:url value='/CancelAutoLoginServlet'/>">取消自动登录</a>

</c:if>
</body>
</html>

CancelAutoLoginServlet.java-取消自动登录：

package cn.hncu.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CancelAutoLoginServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
        doPost(request, response);
    }

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

//取消自动登录，其实就是删除Cookie
        Cookie cookie = new Cookie("autoLogin", "");
        cookie.setPath(request.getContextPath());//这个路径必须和原来的设置为一样，否则没用的
        cookie.setMaxAge(0);//有效期为0即是删除
        response.addCookie(cookie);
        response.sendRedirect(request.getContextPath()+"/index.jsp");
    }
}

AutoLoginFilter.java-自动登录:

package cn.hncu.filter;

import java.io.IOException;
import java.net.URLDecoder;

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.Cookie;
import javax.servlet.http.HttpServletRequest;

import cn.hncu.domain.User;

public class AutoLoginFilter implements Filter {

@Override
public void init(FilterConfig filterConfig) throws ServletException {
    }

@Override
public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
if(req.getSession().getAttribute("user")==null){//还没有登录，帮你自动登录
            Cookie cs[] = req.getCookies();
if(cs!=null){
for(Cookie c :cs){//找"autoLogin"这个cookie
if(c.getName().equals("autoLogin")){
                        String str = c.getValue();
                        String vals[] = str.split("#!#");
                        String name = URLDecoder.decode(vals[0], "utf-8");
                        String pwd = URLDecoder.decode(vals[1], "utf-8");

//...
//这里应该再去后台数据库验证是否登录能够成功,这里我就直接以两者相等来判断
if(name.equals(pwd)){//如果成功则返回一个user对象
                            User user = new User();
                            user.setName(name);
                            user.setPwd(pwd);
                            req.getSession().setAttribute("user", user);
break;
                        }
                    }
                }
            }

        }
        chain.doFilter(req, response);//放行
    }
@Override
public void destroy() {
    }
}

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 
xmlns="http://java.sun.com/xml/ns/javaee" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
 http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<display-name></display-name>
<filter>
<filter-name>character</filter-name>
<filter-class>cn.hncu.pubs.CharacterFilter</filter-class>
<init-param>
<param-name>charset</param-name>
<param-value>utf-8</param-value>    
</init-param>
</filter>
<filter>
<filter-name>autoLogin</filter-name>
<filter-class>cn.hncu.filter.AutoLoginFilter</filter-class>
</filter>


<filter-mapping>
<filter-name>character</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>autoLogin</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>


<servlet>
<servlet-name>CancelAutoLoginServlet</servlet-name>
<servlet-class>cn.hncu.servlet.CancelAutoLoginServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>cn.hncu.servlet.LoginServlet</servlet-class>
</servlet>


<servlet-mapping>
<servlet-name>CancelAutoLoginServlet</servlet-name>
<url-pattern>/CancelAutoLoginServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
</servlet-mapping>

<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

代码里面都有注释!

实现的功能就是自动登录和取消自动登录。

主要利用了过滤器。还有用到cookie技术。

完整项目链接:
https://github.com/chenhaoxiang/Java/tree/master/myAutoLoginWeb
myAutoLoginWeb.zip文件

转载请附上原文博客链接：

http://blog.csdn.net/qq_26525215