java单点登录的实现

单点登录首先首先要保持数据库数据的一致性，这个实现方式很多我就不多废话了。

刚开始我的想法是在一个应用中登陆的时候发送一个http请求到另一个应用保证两个应用同时拥有session，后来考虑到session过期不同步的问题只能放弃。为了保持session的完全同步我只能求助于cookie，首先说一下思路：
1.为了两个应用个应用能同时访问到cookie，cookie设置的时候要设置path在根目录(同一个服务器下的不
同应用,不在同一个应用下可以用共用域名比如说 .baidu.com)，必须保证cookie在统一一个域下
2.在访问一个应用的时候首先检测session如果存在就是已经登录保存cookie(保证cookie是最新的)
3.如果session不存在检测cookie如果cooki不存在说明在另一应用中也没有登录
4.cookie存在检测创建时间（当然保存的时候要设置一个时间）如果没有过期就用cookie中保存的用户名密码调用一下登录方法
5.登陆成功保存cookie

为了保证每次请求都能检测我使用了filter下面贴一下filter代码
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;

public class LoginFilter implements Filter {

private String loginInfoPath;
public void destroy() {
   loginInfoPath = null;
}

public void doFilter(ServletRequest sreq, ServletResponse sresp,
    FilterChain chain) throws IOException, ServletException {
   HttpServletRequest req = (HttpServletRequest) sreq;
   HttpServletResponse resp = (HttpServletResponse) sresp;
   Class loginInfoClass = null;
   LoginInfoBase loginInfo = null;
   try {
    loginInfoClass = Class.forName(loginInfoPath);
    loginInfo = (LoginInfoBase) loginInfoClass.newInstance();
   } catch (ClassNotFoundException e) {
    e.printStackTrace();
   } catch (InstantiationException e) {
    e.printStackTrace();
   } catch (IllegalAccessException e) {
    e.printStackTrace();
   }
   loginInfo.setReq(req);
   loginInfo.setResp(resp);
   //session值为空
   if(loginInfo.isSessionEmpty()){
    if(loginInfo.init()){
     boolean loginResult = loginInfo.doLogin();
     if(loginResult){
      loginInfo.saveCookie();
     }
    }
   }else{
    if(loginInfo.init()){
     //另外一套系统已经退出
     if("out".equals(loginInfo.getLoginState())){
      loginInfo.doLogout();
      CookieUtil.delCookie(resp, LoginInfoBase.COOKIE_NAME);
     }
    }
   }
   chain.doFilter(sreq, sresp);
}

public void init(FilterConfig config) throws ServletException {
   this.loginInfoPath = config.getInitParameter("loginInfoPath");
}

public String getLoginInfoPath() {
   return loginInfoPath;
}

public void setLoginInfoPath(String loginInfoPath) {
   this.loginInfoPath = loginInfoPath;
}

}
loginInfoPath 在web.xml中配置指明LoginInfoBase的子类的完整路径用来反射

LoginInfoBase代码：
package com.yt.util;

import java.text.SimpleDateFormat;
import java.util.Date;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public abstract class LoginInfoBase {
public static final String SEPARATION = "-->";
public static final String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";
public static final long COOKIE_TIME = 1800000;
public static final String COOKIE_NAME = "loginInfo";
public static final String COOKIE_PATH = "/";

protected HttpServletRequest req;
protected HttpServletResponse resp;

protected Date sessionTime;
protected String userName;
protected String userPass;
protected String loginState;

public LoginInfoBase() {
   super();
}

public LoginInfoBase(HttpServletRequest req, HttpServletResponse resp) {
   super();
   this.req = req;
   this.resp = resp;
}

public LoginInfoBase(String userName, String pwd, Date sessionTime) {
   this.userName = userName;
   this.userPass = pwd;
   this.sessionTime = sessionTime;
}

abstract void doLogout();
abstract boolean isSessionEmpty();
abstract boolean doLogin();

public HttpServletRequest getReq() {
   return req;
}
public void setReq(HttpServletRequest req) {
   this.req = req;
}
public HttpServletResponse getResp() {
   return resp;
}
public void setResp(HttpServletResponse resp) {
   this.resp = resp;
}

//初始化登录对象
protected boolean init(){
   String loginInfoStr = CookieUtil.getValue(req, LoginInfoBase.COOKIE_NAME);
   if(loginInfoStr == null || "".equals(loginInfoStr)){
    return false;
   }
   String[] infoArray = loginInfoStr.split(SEPARATION);
   if(infoArray.length>3){
    this.userName = DigestUtil.getFromBASE64(infoArray[0]);
    this.userPass = DigestUtil.getFromBASE64(infoArray[1]);
    this.sessionTime = buildDate(infoArray[2]);
    this.loginState = infoArray[3];
   }
   if(new Date().getTime() - getSessionTime().getTime() > LoginInfo.COOKIE_TIME){
    CookieUtil.delCookie(resp, LoginInfo.COOKIE_NAME);
    return false;
   }
   return true;
}

protected void saveCookie(){
   setSessionTime(new Date());
   setLoginState("in");
   CookieUtil.addCookie(resp, LoginInfo.COOKIE_NAME, toString(), "/");
}

public void clearCookie(){
   setUserName("XX");
   setUserPass("XX");
   setSessionTime(new Date());
   setLoginState("out");
   CookieUtil.addCookie(resp, LoginInfo.COOKIE_NAME, toString(), "/");
}

@Override
public String toString() {
   return DigestUtil.getBASE64(userName)+SEPARATION+DigestUtil.getBASE64(userPass)+SEPARATION+formateSessionTime()+SEPARATION+loginState;
}

private String formateSessionTime(){
   SimpleDateFormat df = new SimpleDateFormat(DATE_FORMAT);
   String timeStr =df.format(sessionTime);
   return timeStr;
}
private Date buildDate(String sessionTime) {
   SimpleDateFormat df = new SimpleDateFormat(DATE_FORMAT);
   Date date = null;
     try {
         date = df.parse(sessionTime); 
     }catch (Exception ex){
         System.out.println(ex.getMessage());
     } 
   return date;
}

public Date getSessionTime() {
   return sessionTime;
}

public void setSessionTime(Date sessionTime) {
   this.sessionTime = sessionTime;
}

public String getUserName() {
   return userName;
}

public void setUserName(String userName) {
   this.userName = userName;
}

public String getUserPass() {
   return userPass;
}

public void setUserPass(String userPass) {
   this.userPass = userPass;
}

public String getLoginState() {
   return loginState;
}

public void setLoginState(String loginState) {
   this.loginState = loginState;
}

}
doLogin(),doLogout(),isSessionEmpty()必须在子类中实现实现
分别用来登录系统，注销系统，判断是否登录

ok，比较乱不懂的可以提问

有人要求Util的代码，无语，贴出来吧

package net.heart.util;

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.net.URLEncoder;

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

public abstract class CookieUtil {

 public static void addCookie(HttpServletResponse response,String name,String value,int maxAge){
  try {
   Cookie cookie=new Cookie(name,URLEncoder.encode(value, "utf-8"));
   cookie.setMaxAge(maxAge);
   response.addCookie(cookie);
   
  } catch (UnsupportedEncodingException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }
 public static String getValue(HttpServletRequest request,String name){
  String value=null;
  Cookie[] cookies=request.getCookies();
  if(cookies!=null){
   for(Cookie cookie:cookies){
    if(name.equals(cookie.getName())){
     try {
      value=URLDecoder.decode(cookie.getValue(),"utf-8");
     } catch (UnsupportedEncodingException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
     }
     break;
    }
   }
  }
  return value;
 }
 public static void delCookie(HttpServletResponse response,String name){
  Cookie cookie=new Cookie(name,"");
  cookie.setMaxAge(0);
  response.addCookie(cookie);
 }
}