通常我們登錄某網站，會有選擇保存幾天，或者是幾個星期不用登錄，之后輸入該網站地址無需登錄直接進入主頁面，那么這就叫做自動登錄，怎么實現呢，下面我以一個小例子來演示一下
登錄頁面：login.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<html>
<head>
</head>
<body>
<form action="login.do">
用戶名：<input type="text" name="username" ><br/>
密 碼：<input type="text" name="password" ><br/>
<input type="submit" value="登錄" /><select name="saveTime">
<option value="366">一年</option>
<option value="183">半年</option>
<option value="30">一個月</option>
<option value="7">一周</option>
</select>
</form>
</body>
</html>
那么從上面可看到可選擇保存自動登錄的期限，可以是一年，半年，一個月，一周，當然這都是以天為單位的
服務類：LoginService
package com.login.servlet;
public class LoginService {
public static boolean login(String username, String password) {
if ("admin".equals(username) && "123456".equals(password)) {
return true;
} else {
return false;
}
}
}
業務處理servlet:LoginServlet
package com.login.servlet;
import java.io.IOException;
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 LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username=request.getParameter("username");
String password=request.getParameter("password");
String savetime=request.getParameter("saveTime");
if(LoginService.login(username, password)){
if(null!=savetime&&!savetime.isEmpty()){
int saveTime=Integer.parseInt(savetime);//這里接受的表單值為天來計算的
int seconds=saveTime*24*60*60;
Cookie cookie = new Cookie("user", username+"=="+password);
cookie.setMaxAge(seconds);
response.addCookie(cookie);
}
request.setAttribute("username",username);
request.getRequestDispatcher("/main.jsp").forward(request,response);
}else{
request.getRequestDispatcher("/index.jsp").forward(request,response);
}
}
}
看清上面處理Cookie的方式步驟：其實這是為第一次登錄該網站時【前提是選擇了保存自動登錄期限時間】處理Cookie,只要這一步處理成功，以后都無需經過這個Servlet因為我們接下來要在請求到達前，從Cookie中取出我們的用戶名和密碼，這樣的話就需要一個過濾器了
package com.login.servlet;
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.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class IndexFilter implements Filter {
public void destroy() {
// TODO Auto-generated method stub
}
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) arg0;
HttpServletResponse response = (HttpServletResponse) arg1;
Cookie[] cookies = request.getCookies();
String[] cooks = null;
String username = null;
String password = null;
if (cookies != null) {
for (Cookie coo : cookies) {
String aa = coo.getValue();
cooks = aa.split("==");
if (cooks.length == 2) {
username = cooks[0];
password = cooks[1];
}
}
}
if (LoginService.login(username, password)) {
request.getSession().setAttribute("username",username);
response.sendRedirect("main.jsp");
//request.getRequestDispatcher("/main.jsp").forward(request, response);
}else{
arg2.doFilter(request,response );
}
}
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub
}
}
我這里所說的請求到達之前，不是指的某個路徑匹配的servlet而是指的就是在輸入網址到達登錄頁面前就要進行自動登錄的處理，那么web.xml中應該怎么配置呢
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
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_2_5.xsd">
<filter>
<filter-name>loginFilter</filter-name>
<filter-class>com.login.servlet.IndexFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>loginFilter</filter-name>
<url-pattern>/index.jsp</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>com.login.servlet.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/login.do</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>login.jsp</welcome-file>
</welcome-file-list>
</web-app>
看見了沒有，上面的filter匹配路徑只是針對一個頁面，與通常寫/*匹配所有請求到達之前是不一樣的寫法哦
主頁面：main.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<html>
<head>
<title>My JSP 'maiin.jsp' starting page</title>
</head>
<body>
登錄成功，歡迎${username}的到來
</body>
</html>
輸入地址：http://localhost:8080/WebApp/login.jsp，出現登錄頁面
然后輸入：admin,123456 ，選擇一個保存日期
這樣第一次登錄成功之后，是經由LoginServlet處理了，由於選擇了日期，所以Cookie中保存了用戶信息，所以之后再輸入同樣地址后，不會出現登錄頁面，就不再經過LoginServlet處理【因為LoginServlet處理的是登陸頁面上登錄按鈕請求的】，而直接提前交由IndexFilter處理，直接進入主頁面，明白了么