getIdentifier method of PersistenceUnitUtil not working for Composite keys - jpa

Question

I am getting below error when trying to retrieve identity using getIdentifier method of PersistenceUnitUtil. Is there anything I am doing wrong.
Local Exception Stack:
Exception [EclipseLink-0] (Eclipse Persistence Services - 2.4.2.v20130514-5956486): org.eclipse.persistence.exceptions.DescriptorException
Exception Description: An internal error occurred accessing the primary key object [202].
Internal Exception: java.lang.NullPointerException
Descriptor: RelationalDescriptor(com.sample.Person --> [DatabaseTable(PERSON)])
at org.eclipse.persistence.exceptions.DescriptorException.errorUsingPrimaryKey(DescriptorException.java:1923)
at org.eclipse.persistence.internal.jpa.CMP3Policy$FieldAccessor.setValue(CMP3Policy.java:686)
at org.eclipse.persistence.descriptors.CMPPolicy.createPrimaryKeyInstance(CMPPolicy.java:453)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.getIdentifier(EntityManagerFactoryImpl.java:75)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getIdentifier(EntityManagerFactoryDelegate.java:679)
at com.sample.PersistenceUtil.getEntityIdentifier(PersistenceUtil.java:27)
at com.sample.PersistenceUtil.getEntityIdentifier(PersistenceUtil.java:18)
at com.sample.OverrideUtilTest.canconfirmEntityEqualsforCompositeId2(OverrideUtilTest.java:147)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
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.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
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$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: java.lang.NullPointerException
at org.eclipse.persistence.internal.jpa.CMP3Policy$FieldAccessor.setValue(CMP3Policy.java:682)
... 29 more
The code sample I am trying is this:
#Entity
#IdClass(PersonPK.class)
#Table(name = "PERSON")
public class Person {
#Id
#Column(name = "CODE_C")
private String code;
#Column(name = "NAME_C")
private String name;
#Id
#Column(name = "COUNTRY_C")
private String country;
public Person() {
}
public Person(String code, String country) {
this.code = code;
this.country = country;
}
public String getCode() {
return this.code;
}
public String getCountry() {
return this.country;
}
}
public class PersonPK implements Serializable {
private static final long serialVersionUID = 1L;
private final String code;
private final String country;
public PersonPK(String city, String country) {
super();
this.code = city;
this.country = country;
}
#Override
public boolean equals(Object object) {
return super.equals (object);
}
#Override
public int hashCode() {
return super.hashCode();
}
}
The code to retrieve identity I am using is
getEntityManagerFactory(persistenceUnitName).getPersistenceUnitUtil()
.getIdentifier(entity);
Any help is appreciated

Answer 1

The primary key class must be public and must have a public no-arg constructor.
Hibernate message in similar situation is a little bit more informative
javax.persistence.PersistenceException: org.hibernate.InstantiationException: No default constructor for entity: : PersonPK
Solution: Add default constructor to PersonPK