tomca7上で動いているwichetがエラーになったのでworkフォルダを消して対処した話

tomcatを再起動したところ、wichetアプリケーションで以下のエラーが出ました。

5 22, 2015 5:35:39 午後 org.apache.catalina.session.StandardManager startInternal
重大: 永続記憶装置からセッションをロード中の例外です
java.lang.ExceptionInInitializerError
        at sun.misc.Unsafe.ensureClassInitialized(Native Method)
        at sun.reflect.UnsafeFieldAccessorFactory.newFieldAccessor(UnsafeFieldAccessorFactory.java:43)
        at sun.reflect.ReflectionFactory.newFieldAccessor(ReflectionFactory.java:142)
        at java.lang.reflect.Field.acquireFieldAccessor(Field.java:1082)
        at java.lang.reflect.Field.getFieldAccessor(Field.java:1063)
        at java.lang.reflect.Field.getLong(Field.java:605)
        at java.io.ObjectStreamClass.getDeclaredSUID(ObjectStreamClass.java:1663)
        at java.io.ObjectStreamClass.access$700(ObjectStreamClass.java:72)
        at java.io.ObjectStreamClass$2.run(ObjectStreamClass.java:480)
        at java.io.ObjectStreamClass$2.run(ObjectStreamClass.java:468)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.io.ObjectStreamClass.<init>(ObjectStreamClass.java:468)
        at java.io.ObjectStreamClass.lookup(ObjectStreamClass.java:365)
        at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:602)
        at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1623)
        at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1518)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1774)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351)
        at java.io.ObjectInputStream.readArray(ObjectInputStream.java:1707)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1345)
        at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1993)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1918)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1801)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371)
        at org.apache.wicket.protocol.http.SecondLevelCacheSessionStore$SecondLevelCachePageMap.readObject(SecondLevelCacheSessionStore
.java:421)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:483)
        at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:1017)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1896)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1801)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371)
        at org.apache.catalina.session.StandardSession.readObject(StandardSession.java:1619)
        at org.apache.catalina.session.StandardSession.readObjectData(StandardSession.java:1084)
        at org.apache.catalina.session.StandardManager.doLoad(StandardManager.java:282)
        at org.apache.catalina.session.StandardManager.load(StandardManager.java:202)
        at org.apache.catalina.session.StandardManager.startInternal(StandardManager.java:489)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5501)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:649)
        at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:1081)
        at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1877)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
        at XXXXXX
        ... 53 more

どうやらセッション？を消せば良い模様

以下のコマンドで対処しました。

service tomcat7 stop
rm -rf /usr/share/tomcat7/work/
service tomcat7 start

おそらくアプリケーション側でエラーが出た画面の serialVersionUID をよしなに設定するのがベストのようです。