Failed to replicate session + entity hashCode NullPointer exception

[balazska]

Hi!

I Would like to setup http session replication on Seam 2.2.0GA + JBoss 5.1 environment and
I get the following exception:



Failed to replicate session s5hL7mXiY499rXdsivCdTA__.node007
java.lang.NullPointerException
     at clustertest.entity.Person.hashCode(Person.java:78)
     at java.util.HashMap$Entry.hashCode(HashMap.java:720)
     at java.util.AbstractMap.hashCode(AbstractMap.java:461)
     at org.jboss.ha.framework.server.SimpleCachableMarshalledValue.<init>(SimpleCachableMarshalledValue.java:74)
     at org.jboss.ha.framework.server.SimpleCachableMarshalledValue.<init>(SimpleCachableMarshalledValue.java:80)
     at org.jboss.web.tomcat.service.session.distributedcache.spi.SessionSerializationFactory.createMarshalledValue(SessionSerializationFactory.java:74)
     at org.jboss.web.tomcat.service.session.distributedcache.impl.jbc.AbstractJBossCacheService.getMarshalledValue(AbstractJBossCacheService.java:635)
     at org.jboss.web.tomcat.service.session.distributedcache.impl.jbc.SessionBasedJBossCacheService.storeSessionAttributes(SessionBasedJBossCacheService.java:124)
     at org.jboss.web.tomcat.service.session.distributedcache.impl.jbc.SessionBasedJBossCacheService.storeSessionAttributes(SessionBasedJBossCacheService.java:37)
     at org.jboss.web.tomcat.service.session.distributedcache.impl.jbc.AbstractJBossCacheService.storeSessionData(AbstractJBossCacheService.java:403)
     at org.jboss.web.tomcat.service.session.ClusteredSession.processSessionReplication(ClusteredSession.java:1166)
     at org.jboss.web.tomcat.service.session.JBossCacheManager.processSessionRepl(JBossCacheManager.java:1937)
     at org.jboss.web.tomcat.service.session.JBossCacheManager.storeSession(JBossCacheManager.java:309)
     at org.jboss.web.tomcat.service.session.InstantSnapshotManager.snapshot(InstantSnapshotManager.java:51)
     at org.jboss.web.tomcat.service.session.ClusteredSessionValve.handleRequest(ClusteredSessionValve.java:147)
     at org.jboss.web.tomcat.service.session.ClusteredSessionValve.invoke(ClusteredSessionValve.java:94)
     at org.jboss.web.tomcat.service.session.JvmRouteValve.invoke(JvmRouteValve.java:88)
     at org.jboss.web.tomcat.service.session.LockingValve.invoke(LockingValve.java:62)
     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)
     at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:92)
     at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.process(SecurityContextEstablishmentValve.java:126)
     at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:70)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
     at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:330)
     at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:436)
     at org.apache.coyote.ajp.AjpProtocol$AjpConnectionHandler.process(AjpProtocol.java:384)
     at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
     at java.lang.Thread.run(Thread.java:619)



and Person entity:


@Roles( { @Role(name = "sessionPerson", scope = ScopeType.SESSION) })
@Name("person")
@Entity
public class Person implements Serializable {

     private static final long serialVersionUID = 5L;

     @Id
     @GeneratedValue
     private Long id;

     private String name;


     public Long getId() {
          return id;
     }

     public void setId(Long id) {
          this.id = id;
     }

     public String getName() {
          return name;
     }

     public void setName(String name) {
          this.name = name;
     }

     
     @Override
     public boolean equals(Object other) {
          if ((this == other))
               return true;
          if ((other == null))
               return false;
          if (!(other instanceof Person))
               return false;

          return this.getId().equals(((Person) other).getId());
     }

     @BypassInterceptors
     @Override
     public int hashCode() {
          
               int result = 17;
               result = 37 * result + (int) this.getId().intValue();
               return result;

     }
     

}

[balazska]

without @BypassInterceptors on the hashCode method, I got the same exception

[kapitanpetko]

Your hashCode is not null safe --  it the entity is transient, getId() will return null, leading to a NPE. You should use 0 for calculating the hash code when the field is null. Besides that, PK-based equals and hashCode are not recommended, you should probably use the business key for that (name?).

HTH

[balazska]

thank you!

Why the PK-based equals and hashCode not recommended?

[jeanluc]

Because https://www.hibernate.org/109.html

In a nutshell, they may be called before the id was obtained and if the new entities had been added to a collection, the hashcode of the element will change - this violates the contracts of a number of collections, such as sets.