Memcached保存sessionId

１、把sessionId存放在cookie中，并设定一个有效期；
２、把经过Serializable序列化的对象存放在memcached中，同时设置一个失效时间，比如1小时；
３、每次取会话信息时，先从cookie中取sessionId，如果cookie不存在，则说明会话已过期；如果会话存在，则从memcached中读取会话信息，如果会话信息不存在，则从数据库中读取相关信息，然后放在memcached中，同时设置失效时间；
４、设置一个filter，在每次请求时，更新会话cookie的失效时间；
５、登录时设置一个隐藏的随机数；
６、退出时删除会话cookie，同时从memcached中删除相关的会话；

代码如下：

RequestUtils.java

package com.util;

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

/**

*对cookie读写

public class RequestUtils
{

public static String cookieDomain = "";

public static String cookiePath = "/";

/**
* 获取COOKIE
* @param request
* @param name
*/
public static Cookie getCookie(HttpServletRequest request, String name) {
Cookie[] cookies = request.getCookies();
if(cookies == null)
   return null;
for (int i = 0; i < cookies.length; i++) {
   if (name.equals(cookies[i].getName())) {
    return cookies[i];
   }
}
return null;
}

/**
* 设置COOKIE
* @param request
* @param response
* @param name
* @param value
* @param maxAge
*/
public static void setCookie(HttpServletRequest request, HttpServletResponse response, String name,
String value, int maxAge)
{
Cookie cookie = new Cookie(name, value);
cookie.setMaxAge(maxAge);
if(cookieDomain!=null && cookieDomain.indexOf('.')!=-1){
cookie.setDomain('.' + cookieDomain);
}
cookie.setPath(cookiePath);
response.addCookie(cookie);
}
}

SessionCookieFilter.java

package com.mem.session;

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

import com.util.RequestUtils;

/**

*对每次动态页面的请求时，更新会话cookie的有效期

public class SessionCookieFilter extends HttpServlet implements Filter
{
/**
*
*/
private static final long serialVersionUID = -6516046520244652987L;

private String sessionId = "sid";

private int expiryDate = 30*60;//seconeds

public void doFilter(ServletRequest servletRequest,
   ServletResponse servletResponse, FilterChain filterChain)
   throws IOException, ServletException
{
HttpServletRequest request = (HttpServletRequest) servletRequest;
HttpServletResponse response = (HttpServletResponse) servletResponse;
Cookie cookie = RequestUtils.getCookie(request, sessionId);
if (cookie != null)
{
   String sid = cookie.getValue();
   //设置cookie的有效期
   RequestUtils.setCookie(request, response, sessionId, sid, expiryDate);
}
filterChain.doFilter(request,response);
}

public void init(FilterConfig filterConfig) throws ServletException
{
this.sessionId = filterConfig.getInitParameter("sessionId");

com.util.RequestUtils.cookieDomain = filterConfig.getInitParameter("cookieDomain");
if (com.util.RequestUtils.cookieDomain == null)
{
com.util.RequestUtils.cookieDomain = "";
}

com.util.RequestUtils.cookiePath = filterConfig.getInitParameter("cookiePath");
if (com.util.RequestUtils.cookiePath == null || com.util.RequestUtils.cookiePath.length() == 0)
{
com.util.RequestUtils.cookiePath = "/";
}
}

}

SessionService.java

package com.mem.session;

import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import java.util.Calendar;
import java.util.Date;

import com.danga.MemCached.MemCachedClient;
import com.danga.MemCached.SockIOPool;

/**

*对memcached的操作

public class SessionService {

private static SessionService instance = null;

private SockIOPool pool = null;

private String poolName = "sidsock";

private int expiryTime = 60;//minutes

private Date getExpiryDate()
{
Calendar calendar = Calendar.getInstance();

long time = calendar.getTimeInMillis();
time += expiryTime * 60 * 1000;
calendar.setTimeInMillis(time);

return calendar.getTime();
}

public static synchronized SessionService getInstance() {
if (instance == null) {
instance = new SessionService();
}
return instance;
}

private SessionService() {
ClassLoader cl = Thread.currentThread().getContextClassLoader();
InputStream input = cl.getResourceAsStream("memcached.properties");
Properties props = new Properties();
String serverlist = "127.0.0.1:11211";
try {
   props.load(input);
   serverlist = props.getProperty("serverlist", "127.0.0.1:11211");
   poolName = props.getProperty("poolname", "sidsock");

} catch (Exception e) {
e.printStackTrace();
}

String[] servers = serverlist.split(",");
pool = SockIOPool.getInstance(poolName);
pool.setServers(servers);
pool.setFailover(true);
pool.setInitConn(10);
pool.setMinConn(5);
pool.setMaxConn(250);
pool.setMaintSleep(30);
pool.setNagle(false);
pool.setSocketTO(3000);
pool.setAliveCheck(true);
pool.initialize();
}

public boolean sessionExists(String id)
{
MemCachedClient mc = this.getMemCachedClient();
return mc.keyExists(id);
}
public Map getSession(String id,boolean create)
{
MemCachedClient mc = this.getMemCachedClient();

Map session = (Map) mc.get(id);
if(session == null)
{
   if(create)
   {
    session = new HashMap(5);
    mc.add(id, session,getExpiryDate());
   }
}
return session;
}

public void saveSession(String id, Map session)
{
MemCachedClient mc = this.getMemCachedClient();
if(mc.keyExists(id))
{
   mc.replace(id, session);
}
else
{
   mc.add(id, session);
}
}

public void saveSession(String id, Map session,Date expiryDate)
{
MemCachedClient mc = this.getMemCachedClient();
if(mc.keyExists(id))
{
   mc.replace(id, session,expiryDate);
}
else
{
   mc.add(id, session,expiryDate);
}
}

public void removeSession(String id)
{
MemCachedClient mc = this.getMemCachedClient();
mc.delete(id);
}

public void updateExpiryDate(String id)
{
MemCachedClient mc = this.getMemCachedClient();
Map session = (Map) mc.get(id);
if(session != null)
{
mc.replace(id, session,getExpiryDate());
}
}

private MemCachedClient getMemCachedClient()
{
MemCachedClient mc = new MemCachedClient();
mc.setPoolName(poolName);
mc.setCompressEnable(false);
mc.setCompressThreshold(0);
return mc;
}

protected void finalize()
{
if (this.pool != null)
{
this.pool.shutDown();
}
}

}

MemSession.java

package com.mem.session;

import java.util.Map;

/**

*对会话的操作

public class MemSession
{
//会话ID
private String sid = "";

//存放本会话的所有信息
private Map map = null;

public static MemSession getSession(String sid)
{
MemSession session = null;

session = new MemSession(sid,true);

return session;
}

public static MemSession getSession(String sid,boolean create)
{
MemSession session = null;

session = new MemSession(sid,create);

return session;
}

private MemSession(String sid,boolean create)
{
this.sid = sid;
this.map = SessionService.getInstance().getSession(sid,create);
}

public static boolean sessionExists(String sid)
{
return SessionService.getInstance().sessionExists(sid);
}

public Object getAttribute(String arg0)
{
return this.map.get(arg0);
}

public void invalidate()
{
this.map.clear();
SessionService.getInstance().removeSession(this.sid);
}

public void removeAttribute(String arg0)
{
if(arg0 == null || arg0.trim().length() <= 0)
{
return;
}
this.map.remove(arg0);
SessionService.getInstance().saveSession(this.sid, this.map);
}
public void setAttribute(String arg0, Object arg1)
{
if(arg0 == null || arg0.trim().length() <= 0 || arg1 == null)
{
return ;
}
this.map.put(arg0, arg1);
SessionService.getInstance().saveSession(this.sid, this.map);
}
public void updateExpiryDate(String sid)
{
SessionService.getInstance().updateExpiryDate(sid);
}

}

//SessionUtil.java

package com.mem.session;

import java.io.Serializable;

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

import com.util.RequestUtils;
import com.mem.session.MemSession;

public class SessionUtil
{
public static UserInfo getUserInfo(HttpServletRequest request)
{
Cookie cookie = RequestUtils.getCookie(request, "sid");

if(cookie != null)
{
   String sid = cookie.getValue();
   MemSession session = MemSession.getSession(sid);
   UserInfo userInfo = (UserInfo)session.getAttribute("user_session_flag");

   if(userInfo == null)
   {
    //缓存中已经不存在，则要从数据库中读取，同时存放在缓存中
    userInfo = new UserInfo("hpt321",1,"hpt321");//要从数据库中读取
    session.setAttribute("user_session_flag", userInfo);

    return userInfo;
   }

}
return null;
}

public static void setUserInfo(UserInfo userInfo,HttpServletRequest request,HttpServletResponse response)
{
setAttribute(request, "user_session_flag", userInfo);
}
/**
* 登录返回true;未登录返回false;
* @param request
* @return
*/
public static boolean valideLogin(HttpServletRequest request)
{
Cookie cookie = RequestUtils.getCookie(request, "sid");
if(cookie == null)
{
   return false;
}
else
{
   return true;
}
}
public static void setAttribute(String sid,String key,Object value)
{
//把置放入缓存中
MemSession session = MemSession.getSession(sid);
session.setAttribute(key, value);
}
public static void setAttribute(HttpServletRequest request,String key,Object value)
{
Cookie cookie = RequestUtils.getCookie(request, "sid");
if(cookie != null)
{
//   取出session的ID
   String sid = cookie.getValue();
   //把置放入缓存中
   MemSession session = MemSession.getSession(sid);
   session.setAttribute(key, value);
}
}
public static Object getAttribute(String sid,String key)
{
//把置放入缓存中
MemSession session = MemSession.getSession(sid);
return session.getAttribute(key);
}
public static Object getAttribute(HttpServletRequest request,String key)
{
Cookie cookie = RequestUtils.getCookie(request, "sid");

if(cookie != null)
{
   //取出session的ID
   String sid = cookie.getValue();
   //把置放入缓存中
   MemSession session = MemSession.getSession(sid);
   return session.getAttribute(key);
}
return null;
}
public static void removeAttribute(HttpServletRequest request,String key)
{
Cookie cookie = RequestUtils.getCookie(request, "sid");

if(cookie != null)
{
   //取出session的ID
   String sid = cookie.getValue();
   //把置放入缓存中
   MemSession session = MemSession.getSession(sid);
   session.removeAttribute(key);
}

}
public static void invalidate(HttpServletRequest request)
{
Cookie cookie = RequestUtils.getCookie(request, "sid");

if(cookie != null)
{
   //取出session的ID
   String sid = cookie.getValue();
   //把置放入缓存中
   MemSession session = MemSession.getSession(sid);
   session.invalidate();
}
}

}

//
登录
synchronized(信号量)
{
//验证隐藏的验证码，同时删除随机验证码，避免重复登录
}

//１、此处先得到cookie中已有的会话ID，以便登录后清除memached中的会话信息;

//２、清除前一个登录的会话信息

String sid = java.util.UUID.randomUUID().toString()+serverName+"_"+userId;
//加入serverName，是为了区分多台服务器产生的randomUUID可能相同

  com.util.RequestUtils.setCookie(request, response, "sid", sid, 30*60);

  com.mem.session.SessionUtil.setAttribute(sid, "user_session_flag", userInfo);

//退出

删除会话cookie同时删除memcached中的会话信息

com.mem.session.SessionUtil.invalidate(request);