JPA error: "0 persistence units are found."

[patrik_spiess]

Hello,

I am developing persistance in the system database MaxDB on NWDI 7.1 SP5 with NWDS. I get the following error in Developer Studio:

"0 persistence units are found. Only exactly one persistence unit is supported."

Anybody seen this problem before and knows what it means and how to solve it?

Cheers,

Patrik

[Vlado · Accepted solution]

Guess you have an empty persistence.xml, i.e. one that does not define any persistence unit. If you add one the error should disappear.

HTH!

\-- Vladimir

[patrik_spiess · Accepted solution]

Here is my current persistence.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
	<persistence-unit name="impl_ejb">
		<jta-data-source>SII_DB_ALIAS</jta-data-source>
	</persistence-unit>
</persistence>

[Vlado · Accepted solution]

Hmm... that looks fine.

Where exactly do you see this error? Does it point to some resource in your workspace? Line number or something?

[patrik_spiess · Accepted solution]

Unfortunately, the location is "Unknown". The following error can be found in the PDE runtime error log:

Message: An error occurred while traversing resources.

java.lang.ClassCastException: org.eclipse.jdt.core.dom.QualifiedName
at org.eclipse.jpt.core.internal.jdtutility.EnumArrayDeclarationAnnotationElementAdapter.resolve(EnumArrayDeclarationAnnotationElementAdapter.java:91)
at org.eclipse.jpt.core.internal.jdtutility.EnumArrayDeclarationAnnotationElementAdapter.getValue(EnumArrayDeclarationAnnotationElementAdapter.java:66)
at org.eclipse.jpt.core.internal.jdtutility.EnumArrayDeclarationAnnotationElementAdapter.getValue(EnumArrayDeclarationAnnotationElementAdapter.java:1)
at org.eclipse.jpt.core.internal.jdtutility.MemberAnnotationElementAdapter.getValue(MemberAnnotationElementAdapter.java:43)
at org.eclipse.jpt.core.internal.jdtutility.ShortCircuitAnnotationElementAdapter.getValue(ShortCircuitAnnotationElementAdapter.java:47)
at org.eclipse.jpt.core.internal.content.java.mappings.JavaCascade.updateFromJava(JavaCascade.java:574)
at org.eclipse.jpt.core.internal.content.java.mappings.JavaRelationshipMapping.updateFromJava(JavaRelationshipMapping.java:567)
at org.eclipse.jpt.core.internal.content.java.mappings.JavaSingleRelationshipMapping.updateFromJava(JavaSingleRelationshipMapping.java:592)
at org.eclipse.jpt.core.internal.content.java.mappings.JavaOneToOne.updateFromJava(JavaOneToOne.java:304)
at org.eclipse.jpt.core.internal.content.java.mappings.JavaAttributeMapping.initialize(JavaAttributeMapping.java:80)
at org.eclipse.jpt.core.internal.content.java.JavaPersistentAttribute.updateFromJava(JavaPersistentAttribute.java:564)
at org.eclipse.jpt.core.internal.content.java.JavaPersistentType.updatePersistentFields(JavaPersistentType.java:694)
at org.eclipse.jpt.core.internal.content.java.JavaPersistentType.updatePersistentAttributes(JavaPersistentType.java:677)
at org.eclipse.jpt.core.internal.content.java.JavaPersistentType.updateFromJava(JavaPersistentType.java:671)
at org.eclipse.jpt.core.internal.content.java.JpaCompilationUnit.synchronizePersistentTypes(JpaCompilationUnit.java:406)
at org.eclipse.jpt.core.internal.content.java.JpaCompilationUnit.setFile(JpaCompilationUnit.java:325)
at org.eclipse.jpt.core.internal.content.java.JavaJpaFileContentProvider.buildRootContent(JavaJpaFileContentProvider.java:30)
at org.eclipse.jpt.core.internal.JpaFileContentRegistry.buildContent(JpaFileContentRegistry.java:60)
at org.eclipse.jpt.core.internal.JpaFileContentRegistry.getFile(JpaFileContentRegistry.java:44)
at org.eclipse.jpt.core.internal.JpaProject.createJpaFile(JpaProject.java:630)
at org.eclipse.jpt.core.internal.JpaProject$3.visit(JpaProject.java:497)
at org.eclipse.core.internal.resources.Resource$1.visitElement(Resource.java:57)
at org.eclipse.core.internal.watson.ElementTreeIterator.doIteration(ElementTreeIterator.java:81)
at org.eclipse.core.internal.watson.ElementTreeIterator.doIteration(ElementTreeIterator.java:85)
at org.eclipse.core.internal.watson.ElementTreeIterator.doIteration(ElementTreeIterator.java:85)
at org.eclipse.core.internal.watson.ElementTreeIterator.doIteration(ElementTreeIterator.java:85)
at org.eclipse.core.internal.watson.ElementTreeIterator.doIteration(ElementTreeIterator.java:85)
at org.eclipse.core.internal.watson.ElementTreeIterator.doIteration(ElementTreeIterator.java:85)
at org.eclipse.core.internal.watson.ElementTreeIterator.doIteration(ElementTreeIterator.java:85)
at org.eclipse.core.internal.watson.ElementTreeIterator.doIteration(ElementTreeIterator.java:85)
at org.eclipse.core.internal.watson.ElementTreeIterator.doIteration(ElementTreeIterator.java:85)
at org.eclipse.core.internal.watson.ElementTreeIterator.iterate(ElementTreeIterator.java:126)
at org.eclipse.core.internal.resources.Resource.accept(Resource.java:67)
at org.eclipse.jpt.core.internal.JpaProject.fill(JpaProject.java:504)
at org.eclipse.jpt.core.internal.JpaModelManager.fillJpaProject(JpaModelManager.java:180)
at org.eclipse.jpt.core.internal.JpaModel$1.visit(JpaModel.java:152)
at org.eclipse.core.internal.resources.Resource$1.visitElement(Resource.java:57)
at org.eclipse.core.internal.watson.ElementTreeIterator.doIteration(ElementTreeIterator.java:81)
at org.eclipse.core.internal.watson.ElementTreeIterator.iterate(ElementTreeIterator.java:119)
at org.eclipse.core.internal.resources.Resource.accept(Resource.java:67)
at org.eclipse.jpt.core.internal.JpaModel.fill(JpaModel.java:158)
at org.eclipse.jpt.core.internal.JpaModelManager$WorkspaceBuildJob$1.run(JpaModelManager.java:260)
at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:1797)
at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:1779)
at org.eclipse.jpt.core.internal.JpaModelManager$WorkspaceBuildJob.run(JpaModelManager.java:257)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

[patrik_spiess]

The problem was solved by Vladimir after taking a deep look into my entity code.

The reason was that I had defined the "cascade" attribute of some relationships. What I failed to recognize is that the this attribute expects an array of cascade type constants, not a single constant:

wrong: @OneToOne(cascade = CascadeType.ALL)

right: @OneToOne(cascade = {CascadeType.ALL)}

This caused the JPA tools in DevStudio to crash.

Obvious, isn't it?

[Former Member]

As obvious as many other errors in NW. Thanks for posting the solution

Funnily the wrong worked until i accidently killed my dictionary connection. After adding the connection again, the problem arose.

[Former Member]

Have you got a Dictionary assigned in your JPA project settings?