I've been upgrading a Grails 1.3.7 application to 2.4.4, using Hibernate 3 due to Spring Security being incompatible with the hibernate4 plugin, and have run into issues with this kind of stacktrace at runtime:
java.lang.ClassCastException: com.xxxxxx.grails.domain.WorkflowStepDescription_$$_javassist_1 cannot be cast to javassist.util.proxy.ProxyObject
at org.codehaus.groovy.grails.orm.hibernate.proxy.GroovyAwareJavassistLazyInitializer.createProxyInstance(GroovyAwareJavassistLazyInitializer.java:107)
at org.codehaus.groovy.grails.orm.hibernate.proxy.GroovyAwareJavassistLazyInitializer.getProxy(GroovyAwareJavassistLazyInitializer.java:134)
at org.codehaus.groovy.grails.orm.hibernate.proxy.GroovyAwareJavassistProxyFactory.getProxy(GroovyAwareJavassistProxyFactory.java:64)
at org.codehaus.groovy.grails.orm.hibernate.persister.entity.GroovyAwareSingleTableEntityPersister.createProxy(GroovyAwareSingleTableEntityPersister.java:49)
at org.hibernate.event.def.DefaultLoadEventListener.createProxyIfNecessary(DefaultLoadEventListener.java:360)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:281)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:152)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:1090)
at org.hibernate.impl.SessionImpl.internalLoad(SessionImpl.java:1038)
at org.hibernate.type.EntityType.resolveIdentifier(EntityType.java:630)
at org.hibernate.type.EntityType.resolve(EntityType.java:438)
at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:139)
at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:982)
at org.hibernate.loader.Loader.doQuery(Loader.java:857)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:274)
at org.hibernate.loader.Loader.doList(Loader.java:2542)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2276)
at org.hibernate.loader.Loader.list(Loader.java:2271)
at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1716)
at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347)
Searching around indicates that this is due to conflicts with Javassist versions, and sure enough, I have two different versions in my built JAR:
hibernate-jpa-2.0-api-1.0.1.Final.jar
hibernate-jpa-2.1-api-1.0.0.Final.jar
Looking at grails dependency-report, it looks like the dependency on 2.1 is coming from Grails itself:
The one from Hibernate 3.6.10.18:
+--- org.grails.plugins:hibernate:3.6.10.18
| \--- org.hibernate:hibernate-entitymanager:3.6.10.Final
| \--- org.hibernate:hibernate-core:3.6.10.Final
| \--- org.hibernate.javax.persistence:hibernate-jpa-2.0-api:1.0.1.Final
The one from Grails 2.4.4:
+--- org.grails:grails-plugin-datasource:2.4.4
| \--- org.grails:grails-core:2.4.4
| \--- org.hibernate.javax.persistence:hibernate-jpa-2.1-api:1.0.0.Final
I know that Grails 2.4.4 has the option of using Hibernate 3... can I avoid this conflict of dependencies, perhaps by downgrading the datasource plugin?
Okay, this is so convoluted that I doubt it'll help anybody else, but I solved it - I noticed that this exception only happened on one particular domain class. After a lot of trial and error, I found it was because the class had a property called "handler", which I can only assume is conflicted with a method in later versions of javassist. I changed that to "actionHandler", and the errors are gone.
The two JAR versions are no doubt still a problem, but they were a red herring on this issue. Check your domain class property names for anything suspicious!