Question

This is the error when I try to persist an Entity:

com.googlecode.objectify.SaveException: Error saving com.mycomp.simplify.KeyValueVersion@60991f: You cannot create a Key for an object with a null @Id. Object was com.mycomp.simplify.Key@1bf3d87
    at com.googlecode.objectify.impl.Transmog.save(Transmog.java:102)
    at com.googlecode.objectify.impl.Concret

> Blockquote

eEntityMetadata.save(ConcreteEntityMetadata.java:150)
    at com.googlecode.objectify.impl.engine.WriteEngine.save(WriteEngine.java:68)
    at com.googlecode.objectify.impl.cmd.SaverImpl.entities(SaverImpl.java:56)
    at com.googlecode.objectify.impl.cmd.SaverImpl.entity(SaverImpl.java:33)
    at com.mycomp.simplify.core.ObjectifyGenericDao.put(ObjectifyGenericDao.java:52)
    at com.mycomp.simplify.SimplifyImpl.access$0(SimplifyImpl.java:1)
    at com.mycomp.simplify.SimplifyImpl$1.run(SimplifyImpl.java:43)
    at com.mycomp.simplify.SimplifyImpl$1.run(SimplifyImpl.java:1)
    at com.googlecode.objectify.impl.cmd.ObjectifyImpl.transactOnce(ObjectifyImpl.java:255)
    at com.googlecode.objectify.impl.cmd.ObjectifyImpl.transactNew(ObjectifyImpl.java:232)
    at com.googlecode.objectify.impl.cmd.ObjectifyImpl.transactNew(ObjectifyImpl.java:222)
    at com.googlecode.objectify.impl.cmd.ObjectifyImpl.transact(ObjectifyImpl.java:214)
    at com.googlecode.objectify.util.cmd.ObjectifyWrapper.transact(ObjectifyWrapper.java:165)
    at com.mycomp.simplify.SimplifyImpl.put(SimplifyImpl.java:37)
    at com.mycomp.simplify.ResourceTest.testCreateFetch(ResourceTest.java:36)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: java.lang.IllegalArgumentException: You cannot create a Key for an object with a null @Id. Object was com.mycomp.simplify.Key@1bf3d87
    at com.googlecode.objectify.impl.translate.EntityClassTranslator.getRawKey(EntityClassTranslator.java:160)
    at com.googlecode.objectify.ObjectifyFactory.getRawKey(ObjectifyFactory.java:270)
    at com.googlecode.objectify.impl.translate.EntityReferenceTranslatorFactory$1.saveValue(EntityReferenceTranslatorFactory.java:39)
    at com.googlecode.objectify.impl.translate.EntityReferenceTranslatorFactory$1.saveValue(EntityReferenceTranslatorFactory.java:1)
    at com.googlecode.objectify.impl.translate.ValueTranslator.savePropertyValue(ValueTranslator.java:51)
    at com.googlecode.objectify.impl.translate.PropertyValueNodeTranslator.saveAbstract(PropertyValueNodeTranslator.java:38)
    at com.googlecode.objectify.impl.translate.AbstractTranslator.save(AbstractTranslator.java:38)
    at com.googlecode.objectify.impl.TranslatableProperty.executeSave(TranslatableProperty.java:145)
    at com.googlecode.objectify.impl.translate.ClassTranslator.saveMap(ClassTranslator.java:94)
    at com.googlecode.objectify.impl.translate.MapNodeTranslator.saveAbstract(MapNodeTranslator.java:38)
    at com.googlecode.objectify.impl.translate.AbstractTranslator.save(AbstractTranslator.java:38)
    at com.googlecode.objectify.impl.Transmog.saveToNode(Transmog.java:109)
    at com.googlecode.objectify.impl.Transmog.save(Transmog.java:96)
    ... 39 more

Answer 1

You have an entity reference in your entity class which has no id. That is, something like this:

@Entity
class MyEntity {
    @Id Long id;
    OtherEntity other;   // this thing has a null id
}

Objectify can’t save a Key for OtherEntity because it can’t create the Key.

This is one reason (of several) why this ability to place direct entity references is being removed in the next release of Objectify. You will want to change your code to this:

@Entity
class MyEntity {
    @Id Long id;
    Ref<OtherEntity> other;
    public OtherEntity getOther() { return other.get(); }
    public void setOther(OtherEntity value) { this.other = Ref.create(value); }
}

This pattern eliminates confusion because you’ll get a clear exception immediately when you try to create an invalid Ref.