I am trying to map an entity as a java.lang.Object. I need to do this because I want the "value" to contain different types of objects.

Using hibernate 3.0

I tried this mapping
Mapping documents:
<property name="Value"
column="VALUE"
type="java.lang.Object"
unique="false"
/>

But I was not able to get that to work. If anyone thinks this should work please let me know. I saw a post about something similar suggesting type="byte[]". I used that and I can get the mapping loaded. However, when I try to create and save (session.save(x)) an instance of the class to the database I get the following exception. The actual type of the object in the value field is a java.lang.String so I'm assuming hibernate doesn't like my mapping of byte[].

b]6:03:10,093 ERROR [main] (ValueFactory.java:53) - Error creating value for com.convera.adminApi.dataModel.properties.StringProperty with value of test string value Exception:java.lang.String
java.lang.ClassCastException: java.lang.String
at org.hibernate.type.BinaryType.deepCopyNotNull(BinaryType.java:115)
at org.hibernate.type.MutableType.deepCopy(MutableType.java:25)
at org.hibernate.type.TypeFactory.deepCopy(TypeFactory.java:290)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:227)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:160)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:95)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:184)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:173)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:69)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:481)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:476)
at com.convera.adminApi.dataModel.values.ValueFactory.createValue(ValueFactory.java:84)
at com.convera.adminApi.dataModel.values.ValueFactory.createValue(ValueFactory.java:43)
at com.convera.adminApi.dataModel.values.ValuesTest.testCreateStringValue(ValuesTest.java:102)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at junit.framework.TestCase.runTest(TestCase.java:154)
at junit.framework.TestCase.runBare(TestCase.java:127)
at junit.framework.TestResult$1.protect(TestResult.java:106)
at junit.framework.TestResult.runProtected(TestResult.java:124)
at junit.framework.TestResult.run(TestResult.java:109)
at junit.framework.TestCase.run(TestCase.java:118)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:478)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:344)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)
[/b]

Name and version of the database you are using:
MySql 3.1.10

I'd appreciate any help on this. So if anyone knows how to map an entity to just a plain java.lang.Object, please let me know.
Thanks
Doal Miller
[/b]

Are all your values Serializable? If so, have you tried using:-

<property name="Value"
column="VALUE"
type="serializable"
unique="false"
/>

Thanks for your suggestion. All the objects that go into the "value" field are Serializable. They are mostly wrapper objects (Integer, Boolean, Double, etc...) and String.

Using type="serializable" I got to the point where I can create the containing objects in the database, and everything looks good there. The problem I am having now is I get an exception when I try to retrieve the containing objects from the database. Exception is below. AbstractValue is the containing object (note that its a concrete class now). "value" is the field which contains the entity that is being mapped as serializable.

Any help or suggestions will be appreciated. Thanks

Mapping documents:
<property name="Value"
column="VALUE"
type="serializable"
unique="false"
/>
org.hibernate.PropertyAccessException: Exception occurred inside setter of com.convera.adminApi.dataModel.values.AbstractValue.Value
at org.hibernate.property.BasicPropertyAccessor$BasicSetter.set(BasicPropertyAccessor.java:51)
at org.hibernate.tuple.AbstractTuplizer.setPropertyValues(AbstractTuplizer.java:207)
at org.hibernate.tuple.PojoTuplizer.setPropertyValues(PojoTuplizer.java:176)
at org.hibernate.persister.entity.BasicEntityPersister.setPropertyValues(BasicEntityPersister.java:2919)
at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:113)
at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:530)
at org.hibernate.loader.Loader.doQuery(Loader.java:436)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:218)
at org.hibernate.loader.Loader.doList(Loader.java:1593)
at org.hibernate.loader.Loader.list(Loader.java:1577)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:395)
at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:271)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:844)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:74)
at com.convera.adminApi.dataModel.values.ValueFactory.getValueById(ValueFactory.java:229)
at com.convera.adminApi.dataModel.values.ValueFactory.deleteValue(ValueFactory.java:176)
at com.convera.adminApi.dataModel.values.ValueFactory.deleteValue(ValueFactory.java:156)
at com.convera.adminApi.dataModel.values.ValuesTest.testCreateStringValue(ValuesTest.java:116)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at junit.framework.TestCase.runTest(TestCase.java:154)
at junit.framework.TestCase.runBare(TestCase.java:127)
at junit.framework.TestResult$1.protect(TestResult.java:106)
at junit.framework.TestResult.runProtected(TestResult.java:124)
at junit.framework.TestResult.run(TestResult.java:109)
at junit.framework.TestCase.run(TestCase.java:118)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:478)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:344)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.hibernate.property.BasicPropertyAccessor$BasicSetter.set(BasicPropertyAccessor.java:40)
... 30 more
Caused by: java.lang.NullPointerException
at com.convera.adminApi.dataModel.values.AbstractValue.setValue(AbstractValue.java:80)
... 35 more

Again thanks for you help. It all seems to be working now. My last problem was caused by some code of mine that wasn't protecting against null values.

So type="serializable" looks like the way to map entitys to generic "object" type.

Thanks

word of warning...

be very careful doinf this. The approach is fine for primitive wrappers and such as you stated, but is problematic for classes which might change their class def and/or serial version between storing and subsequent loading