Hibernate 5 FetchType EAGER vs. LAZY

Question

I have a Spring 4.2 web-app with Hibernate 5 with Hibernate-Annotations. The entities seem fine, and now I have a whole bunch of DAO classes, and JUnit4 tests to test these DAO's.

With some of my classes, I have FK mappings to parent objects as follows:

public class MyDataEntity extends BaseEntity
{
    @Id
    @Column(name = "row_id")
    private long rowId;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "parent_id")
    private ParentEntity parent;
}

We can presume, that there are other basic fields, and we have getters/setters for all of them, and a hashCode, equals, and toString methods as well.

In a test getting back MyDataEntity, I get an error message back like:

org.hibernate.HibernateException: HHH000142: Javassist Enhancement failed: com.tomholmes.server.model.common.ParentEntity
at org.hibernate.proxy.pojo.javassist.JavassistProxyFactory.getProxy(JavassistProxyFactory.java:130)
at org.hibernate.tuple.entity.AbstractEntityTuplizer.createProxy(AbstractEntityTuplizer.java:666)
at org.hibernate.persister.entity.AbstractEntityPersister.createProxy(AbstractEntityPersister.java:4461)
at org.hibernate.event.internal.DefaultLoadEventListener.createProxyIfNecessary(DefaultLoadEventListener.java:336)
at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:257)
at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:137)
at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1129)
at org.hibernate.internal.SessionImpl.internalLoad(SessionImpl.java:1022)
at org.hibernate.type.EntityType.resolveIdentifier(EntityType.java:632)
at org.hibernate.type.EntityType.resolve(EntityType.java:424)
at org.hibernate.engine.internal.TwoPhaseLoad.doInitializeEntity(TwoPhaseLoad.java:154)
at org.hibernate.engine.internal.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:128)
at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:1132)
at org.hibernate.loader.Loader.processResultSet(Loader.java:992)
at org.hibernate.loader.Loader.doQuery(Loader.java:930)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:336)
at org.hibernate.loader.Loader.doList(Loader.java:2611)
at org.hibernate.loader.Loader.doList(Loader.java:2594)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2423)
at org.hibernate.loader.Loader.list(Loader.java:2418)
at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:109)
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1774)
at org.hibernate.internal.CriteriaImpl.list(CriteriaImpl.java:363)
at com.tomholmes.server.dao.common.MyDataDaoImpl.getMyDataListBySubject(MyDataDaoImpl.java:105)
at com.tomholmes.server.dao.common.MyDataDaoTest.testListBySubject(MyDataDaoTest.java:308)
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:497)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:254)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:193)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: java.lang.ClassCastException: com.agmednet.server.model.common.TrialEntity_$$_javassist_29 cannot be cast to javassist.util.proxy.Proxy
at org.hibernate.proxy.pojo.javassist.JavassistProxyFactory.getProxy(JavassistProxyFactory.java:123)
... 53 more

The simple fix to this would be to change the FetchType from LAZY to EAGER and the error message goes away.

I know I did some research on this before, but I don't rememeber what I found. Generally, when I get an object from the database, I am taking that object, converting it to JSON and sending it to the front-end. I may not always need the ParentEntity record. If I am getting a record from "MyData" on the back-end, and I plan on getting the Parent at a later time, then I should be able to just lazy-load it.

My boss, would prefer I do lazy-loading, and I can understand not getting a large object when we don't need to, but I need to avoid getting this error, so maybe I just need to tweak my configuration to make lazy-loading work. Or, if I can't use lazy-loading, then I just need a reason I can explain.

Thanks for the help!

Can you check your classpath and post all the jars matching the following pattern `javassist*jar`? — Gergely Bacso, Jan 07 '16 at 21:04
Check for the version compatibility of Hibernate with Javassist. And does `com.tomholmes.server.model.common.ParentEntity` have a public or package private no args constructor which is needed, when lazy loading is enabled? — Tiny, Jan 07 '16 at 21:10
So, I checked "javassist" and found I have: groupId: org.javassist, artifactId: javassist, version: 3.18.0-GA in my entity pom.xml file. ParentEntity is a fairly standard Hibernate Entity Bean with annotations, so there is no public or private constructor with no args. I can put a public constructor explicitly in that class to see if that would help. — tjholmes66, Jan 08 '16 at 16:54
SOLVED: You were both correct it was javassist. In my app, I was pulling in another project as a dependency, and that was using javassist 3.12 but my DAO code in the pom.xml had 3.18 ... so once were both set to the latest version ... it worked .... — tjholmes66, Jan 08 '16 at 20:48

Hibernate 5 FetchType EAGER vs. LAZY

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