Hi,

I have a scenario, where an inheritance-strategy using SINGLE_TABLE or JOINED perfectly works, but TABLE_PER_CLASS throws a NullPointerException.

I wonder if this is meant to be this way or if I have an error somewhere.
This is my class-structure:

I have a Entity called ClearingItem that has a reference to a discount-entity. This discount-entity might be either one object inheriting DiscountBase or one object inheriting FullDiscount. The FullDiscount-Objects always have an aggregation to one DiscountBase-Object. Every time I try to access the DiscountBase in one of the FullDiscount-Objects I get a NPE, because the reference has not been loaded. The funny thing is, it is either one way or another - that means either the FixedDiscount-tree works or fails or the PercentagedDiscount-tree works or fails, but it´s never mixed.

I attached an excerpt of my classes, but I reduced it to the necessary getters and the class-annotations

## Class BaseEntity
@MappedSuperclass
public abstract class BaseEntit {

protected long id = 0;
protected long version = 0L;

@Id @GeneratedValue(strategy=GenerationType.SEQUENCE)
public long getId(){
return id;
}

...
}


## Class Discount
@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public abstract class Discount extends BaseEntity implements Discountable { ...
}

## Class DiscountBase
@Entity
public abstract class DiscountBase extends Discount {
...
}

## Class FullDiscount
@Entity
public abstract class FullDiscount extends Discount {
...
}

## Class FixedDiscountBase
@Entity
@Table(name="fixed_discount_base")
public class FixedDiscountBase extends DiscountBase implements IFixedDiscount {
}

## Class PercentagedDiscountBase
@Entity
@Table(name="percentaged_discount_base")
public class PercentagedDiscountBase extends DiscountBase implements IPercentagedDiscount {
}

## Class FixedDiscount
@Entity
@Table(name="fixed_discount")
public class FixedDiscount extends Discount {

private FixedDiscountBase base = null;

@ManyToOne
@JoinColumn
public FixedDiscountBase getFixedDiscountBase() {
return base;
}
}

## Class PercentagedDiscount
@Entity
@Table(name="percentaged_discount")
public class PercentagedDiscount extends Discount {

private PercentagedDiscountBase base = null;

@ManyToOne
@JoinColumn
public PercentagedDiscountBase getPercentagedDiscountBase() {
return base;
}
}

##Class ClearingItem
@Entity
public class ClearingItem extends BaseEntity{

private Discount discount = null;

@ManyToOne(cascade = { CascadeType.ALL }, fetch=FetchType.EAGER)
@JoinColumn(nullable=false)
public Discount getDiscount() {
return discount;
}

}


Hibernate version:
3.2.2GA
3.3.0GA for Hibernate-Annotations

Stacktrace:
java.lang.NullPointerException
at FixedDiscount.<init>(FixedDiscount.java:40)
at ClearingItem.<init>(ClearingItem.java:131)
at testPersist(ManualBillingClearingItemPersistenceTests.java:192)
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:597)
at org.testng.internal.MethodHelper.invokeMethod(MethodHelper.java:604)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:470)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:564)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:830)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:125)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)
at org.testng.TestRunner.runWorkers(TestRunner.java:678)
at org.testng.TestRunner.privateRun(TestRunner.java:624)
at org.testng.TestRunner.run(TestRunner.java:495)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:300)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:295)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:275)
at org.testng.SuiteRunner.run(SuiteRunner.java:190)
at org.testng.TestNG.createAndRunSuiteRunners(TestNG.java:792)
at org.testng.TestNG.runSuitesLocally(TestNG.java:765)
at org.testng.TestNG.run(TestNG.java:699)
at org.testng.remote.RemoteTestNG.run(RemoteTestNG.java:73)
at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:122)


Name and version of the database you are using:
HsqlDB 1.8.0.7


So If anyone has an idea, what causes this problem, I´d be glad if you´d let me know.

Thanks
Thomas