用memcached实现session共享，tomcat启动不报错，浏览器访问就报错?报错

在ubuntu虚拟机上用nginx+tomcat做负载均衡，为了实现session的共享，安装了memcached服务，并在tomcat的lib目录下导入了下列jar包：

asm-3.2.jar，couchbase-client-1.2.2.jar，kryo-1.03.jar，kryo-serializers-0.11.jar，memcached-session-manager-1.6.5.jar，memcached-session-manager-tc7-1.6.5.jar，minlog-1.2.jar，msm-kryo-serializer-1.6.5.jar，reflectasm-0.9.jar，spymemcached-2.10.3.jar

在tomcat的context.xml里面添加如下：

<Manager className="de.javakaffee.web.msm.MemcachedBackupSessionManager"  
 memcachedNodes="n1:192.168.126.132:11211,n2:192.168.126.131:11211"
 sticky="false"
 sessionBackupAsync="false"
 lockingMode="auto" 
 requestUriIgnorePattern=".*\.(png|gif|jpg|css|js){1}quot"
 sessionBackupTimeout="1000"    
 transcoderFactoryClass="de.javakaffee.web.msm.serializer.kryo.KryoTranscoderFactory"  
/>

Sep 06, 2016 6:09:45 PM de.javakaffee.web.msm.LockingStrategy onBackupWithoutLoadedSession

WARNING: Found no validity info for session id 1F64837921904BFB8FA17328F56F75BC-n2
Sep 06, 2016 6:09:45 PM org.apache.coyote.http11.AbstractHttp11Processor process
SEVERE: Error processing request
java.lang.NoSuchFieldError: attributes
        at de.javakaffee.web.msm.MemcachedBackupSession.getAttributesFiltered(MemcachedBackupSession.java:514)
        at de.javakaffee.web.msm.BackupSessionTask.call(BackupSessionTask.java:108)
        at de.javakaffee.web.msm.BackupSessionTask.call(BackupSessionTask.java:50)
        at de.javakaffee.web.msm.BackupSessionService$SynchronousExecutorService.submit(BackupSessionService.java:346)
        at de.javakaffee.web.msm.BackupSessionService.backupSession(BackupSessionService.java:205)
        at de.javakaffee.web.msm.MemcachedSessionService.backupSession(MemcachedSessionService.java:1076)
        at de.javakaffee.web.msm.RequestTrackingHostValve.backupSession(RequestTrackingHostValve.java:244)
        at de.javakaffee.web.msm.RequestTrackingHostValve.invoke(RequestTrackingHostValve.java:173)
        at de.javakaffee.web.msm.RequestTrackingHostValve.invoke(RequestTrackingHostValve.java:138)
        at de.javakaffee.web.msm.RequestTrackingHostValve.invoke(RequestTrackingHostValve.java:138)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:442)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1082)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:623)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:745)