可以把session序列化到硬盘 在tomcat的server.xml中配置给你个例子
<Engine name="Catalina" defaultHost="localhost" debug="0">    
        <!-- Define the  virtual host --> 
        <Host name="localhost" debug="0" appBase="c:/www/app"  workDir="c:/www/work" unpackWARs="true" autoDeploy="true">
             <Logger className="org.apache.catalina.logger.FileLogger"
                     directory="c:/www/logs"  prefix="applog."  suffix=".txt"   timestamp="true"/>          
             <Context path="/app" docBase="." debug="0">
                  <Manager className="org.apache.catalina.session.PersistentManager" debug="0" saveOnRestart="true" 
                           maxActiveSessions="-1" minIdleSwap="1800" maxIdleSwap="3600" maxIdleBackup="-1" checkInterval="180">
                       <Store className="org.apache.catalina.session.FileStore" directory="c:/www/session" />
                  </Manager>
             </Context>
        </Host>
    </Engine>