Serialization of formfile uploaded files in Apache + Tomcat cluster sturts

I have been searching for this problem for a long time !!!!!!!!!!

The error is as follows:

Severe: Unable to serialize Delta request for sessionid [7c207deba5350582eff4321ad3089918]
Java. Io. notserializableexception: org. Apache. Struts. Upload. commonsmultipartrequesthandler $ commonsformfile
At java. Io. objectoutputstream. writeobject0 (objectoutputstream. Java: 1081)
At java. Io. objectoutputstream. defaultwritefields (objectoutputstream. Java: 1375)
At java. Io. objectoutputstream. writeserialdata (objectoutputstream. Java: 1347)
At java. Io. objecttoutputstream. writeordinaryobject (objectoutputstream. Java: 1290)
At java. Io. objectoutputstream. writeobject0 (objectoutputstream. Java: 1079)
At java. Io. objectoutputstream. writeobject (objectoutputstream. Java: 302)
At org. Apache. Catalina. Cluster. session. deltarequest $ attributeinfo. writeexternal (deltarequest. Java: 347)
At org. Apache. Catalina. Cluster. session. deltarequest. writeexternal (deltarequest. Java: 264)
At org. Apache. Catalina. Cluster. session. deltamanager. unloaddeltarequest (deltamanager. Java: 715)
At org. Apache. Catalina. Cluster. session. deltamanager. requestcompleted (deltamanager. Java: 1298)
At org. Apache. Catalina. Cluster. tcp. replicationvalve. Send (replicationvalve. Java: 549)
At org. Apache. Catalina. Cluster. tcp. replicationvalve. sendmessage (replicationvalve. Java: 536)
At org. Apache. Catalina. Cluster. tcp. replicationvalve. sendsessionreplicationmessage (replicationvalve. Java: 518)
At org. Apache. Catalina. Cluster. tcp. replicationvalve. sendreplicationmessage (replicationvalve. Java: 428)
At org. Apache. Catalina. Cluster. tcp. replicationvalve. Invoke (replicationvalve. Java: 362)
At org. Apache. Catalina. Valves. errorreportvalve. Invoke (errorreportvalve. Java: 117)
At org. Apache. Catalina. Core. standardenginevalve. Invoke (standardenginevalve. Java: 108)
At org. Apache. Catalina. connector. coyoteadapter. Service (coyoteadapter. Java: 151)
At org. Apache. JK. server. jkcoyotehandler. Invoke (jkcoyotehandler. Java: 200)
At org. Apache. JK. Common. handlerrequest. Invoke (handlerrequest. Java: 283)
At org. Apache. JK. Common. channelsocket. Invoke (channelsocket. Java: 773)
At org. Apache. JK. Common. channelsocket. processconnection (channelsocket. Java: 703)
At org. Apache. JK. Common. channelsocket $ socketconnection. Runit (channelsocket. Java: 895)
At org. Apache. tomcat. util. threads. threadpool $ controlrunnable. Run (threadpool. Java: 685)
At java. Lang. thread. Run (thread. Java: 595)

 

Solution:

PrivateTransientFormfile file = NULL;

Java keyword transient:
Java serialization provides a mechanism for persistence object instances. When a persistent object is stored, there may be a special object data member. We do not want to use the serialization mechanism to save it. To disable serialization on a domain of a specific object, you can add the keyword transient before this domain. Transient is a keyword of the Java language used to indicate that a domain is not part of the object's serialization. When an object is serialized, the value of the transient variable is not included in the serialized representation. However, non-transient variables are included.