JPA with generics and multilevel inheritance. Set Single Table strategy. org.hibernate.MappingException: Could not get constructor

Question

I have problem with my entity.

Everything works fine until I've changed classes inheritance from:

GenericModel -> Insurance -> Doctor
GenericModel -> Insurance -> Nurse

to:

GenericModel -> Insurance -> Liability > Doctor
GenericModel -> Insurance -> Liability > Nurse
GenericModel -> Insurance -> Contract

What have I done:

• I've externalise some Liability releated elements to new Liability class.
• I've added Contract class, which inheritade from Insurance class.
• I've took some functionality/elements related to Liability from Insurance class.

Here are my entities with new structure:

@MappedSuperclass
public abstract class GenericModel<T extends GenericModel> {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY) public Long id;
    @Transient protected Class<T> entityClass;
    public GenericModel() {
        Class obtainedClass = getClass();
        Type genericSuperclass = null;
        for(;;) {
            genericSuperclass = obtainedClass.getGenericSuperclass();
            if(genericSuperclass instanceof ParameterizedType) {
                break;
            }
            obtainedClass = obtainedClass.getSuperclass();
        }
        ParameterizedType genericSuperclass_ = (ParameterizedType) genericSuperclass;
        entityClass = ((Class) ((Class) genericSuperclass_.getActualTypeArguments()[0]));
    }
}

---

@Entity
@DiscriminatorColumn(name="type")
@DiscriminatorValue(value="A")
@Table(name="mi__Insurance")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
public class Insurance<T extends Insurance> extends GenericModel<T> {
    public Insurance() {
        super();
        this.status  = Status.STARTED.getId();
        this.statusDescription = Status.getDescriptionBy(this.status);
        this.statusColor = Status.getColorBy(status);
        this.statusAction = Status.getActionBy(status);
        this.progress = 0;
        this.policyHolder_Answer = null;
        this.policyHolder = 1;
        this.filledParts = 1;
        this.totalParts = 2;
    }
}

---

@Entity
@DiscriminatorValue(value="C")
public class Contract extends Insurance<Contract> {
    public Contract() {
        super();
        this.setColor("danger");
        this.setIcon();
        this.setFormUrl();
    }
}

---

@Entity
@DiscriminatorValue(value="L")
public class Liability extends Insurance<Liability> {
    public Liability() {
        super();
        this.legal_Answer = null;
        this.freely = 0;
        this.mandatory = 0;
        this.hiv = 0;
        this.legal = 0;

    }
}

---

@Entity
@DiscriminatorValue(value="D")
public class Doctor extends Liability {

    public Doctor() {
        super();
        this.setType(Type.DOCTOR);
        this.setColor("success");
        this.setIcon();
        this.setFormUrl();
        this.hiv_Answer = null;
    }
}

---

Everything looks ok for me, but unfortunately I am getting an errors:

play.api.UnexpectedException: Unexpected exception[PersistenceException: [PersistenceUnit: defaultPersistenceUnit] Unable to build EntityManagerFactory]
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: defaultPersistenceUnit] Unable to build EntityManagerFactory
Caused by: org.hibernate.MappingException: Could not get constructor for org.hibernate.persister.entity.SingleTableEntityPersister
Caused by: org.hibernate.InstantiationException: could not instantiate test objectmyInsurance.models.Insurance
Caused by: java.lang.reflect.InvocationTargetException: null
Caused by: java.lang.ClassCastException: sun.reflect.generics.reflectiveObjects.TypeVariableImpl cannot be cast to java.lang.Class

Here is full stack trace:

! @6mped6a12 - Internal server error, for (GET) [/] ->

play.api.UnexpectedException: Unexpected exception[PersistenceException: [PersistenceUnit: defaultPersistenceUnit] Unable to build EntityManagerFactory]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(ApplicationProvider.scala:148) ~[play_2.10.jar:2.2.6]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(ApplicationProvider.scala:112) ~[play_2.10.jar:2.2.6]
        at scala.Option.map(Option.scala:145) ~[scala-library.jar:na]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1.apply(ApplicationProvider.scala:112) ~[play_2.10.jar:2.2.6]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1.apply(ApplicationProvider.scala:110) ~[play_2.10.jar:2.2.6]
        at scala.util.Success.flatMap(Try.scala:200) ~[scala-library.jar:na]
        at play.core.ReloadableApplication$$anonfun$get$1.apply(ApplicationProvider.scala:110) ~[play_2.10.jar:2.2.6]
        at play.core.ReloadableApplication$$anonfun$get$1.apply(ApplicationProvider.scala:102) ~[play_2.10.jar:2.2.6]
        at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) ~[scala-library.jar:na]
        at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) ~[scala-library.jar:na]
        at scala.concurrent.forkjoin.ForkJoinTask$AdaptedRunnableAction.exec(ForkJoinTask.java:1361) ~[scala-library.jar:na]
        at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260) ~[scala-library.jar:na]
        at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339) ~[scala-library.jar:na]
        at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979) ~[scala-library.jar:na]
        at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107) ~[scala-library.jar:na]
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: defaultPersistenceUnit] Unable to build EntityManagerFactory
        at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:915) ~[hibernate-entitymanager-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:890) ~[hibernate-entitymanager-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:57) ~[hibernate-entitymanager-4.2.0.CR1.jar:4.2.0.CR1]
        at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:63) ~[hibernate-jpa-2.0-api.jar:1.0.1.Final]
        at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47) ~[hibernate-jpa-2.0-api.jar:1.0.1.Final]
        at play.db.jpa.JPAPlugin.onStart(JPAPlugin.java:35) ~[play-java-jpa_2.10.jar:2.2.6]
        at play.api.Play$$anonfun$start$1$$anonfun$apply$mcV$sp$1.apply(Play.scala:88) ~[play_2.10.jar:2.2.6]
        at play.api.Play$$anonfun$start$1$$anonfun$apply$mcV$sp$1.apply(Play.scala:88) ~[play_2.10.jar:2.2.6]
        at scala.collection.immutable.List.foreach(List.scala:318) ~[scala-library.jar:na]
        at play.api.Play$$anonfun$start$1.apply$mcV$sp(Play.scala:88) ~[play_2.10.jar:2.2.6]
        at play.api.Play$$anonfun$start$1.apply(Play.scala:88) ~[play_2.10.jar:2.2.6]
        at play.api.Play$$anonfun$start$1.apply(Play.scala:88) ~[play_2.10.jar:2.2.6]
        at play.utils.Threads$.withContextClassLoader(Threads.scala:18) ~[play_2.10.jar:2.2.6]
        at play.api.Play$.start(Play.scala:87) ~[play_2.10.jar:2.2.6]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(ApplicationProvider.scala:139) ~[play_2.10.jar:2.2.6]
        ... 14 common frames omitted
Caused by: org.hibernate.MappingException: Could not get constructor for org.hibernate.persister.entity.SingleTableEntityPersister
        at org.hibernate.persister.internal.PersisterFactoryImpl.create(PersisterFactoryImpl.java:185) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.persister.internal.PersisterFactoryImpl.createEntityPersister(PersisterFactoryImpl.java:135) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:385) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1742) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:94) ~[hibernate-entitymanager-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:905) ~[hibernate-entitymanager-4.2.0.CR1.jar:4.2.0.CR1]
        ... 28 common frames omitted
Caused by: org.hibernate.InstantiationException: could not instantiate test objectmyInsurance.models.Insurance
        at org.hibernate.engine.internal.UnsavedValueFactory.instantiate(UnsavedValueFactory.java:49) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.engine.internal.UnsavedValueFactory.getUnsavedIdentifierValue(UnsavedValueFactory.java:68) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.tuple.PropertyFactory.buildIdentifierProperty(PropertyFactory.java:75) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.tuple.entity.EntityMetamodel.<init>(EntityMetamodel.java:145) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.persister.entity.AbstractEntityPersister.<init>(AbstractEntityPersister.java:507) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        at org.hibernate.persister.entity.SingleTableEntityPersister.<init>(SingleTableEntityPersister.java:146) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.7.0_80]
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) ~[na:1.7.0_80]
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.7.0_80]
        at java.lang.reflect.Constructor.newInstance(Constructor.java:526) ~[na:1.7.0_80]
        at org.hibernate.persister.internal.PersisterFactoryImpl.create(PersisterFactoryImpl.java:163) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        ... 33 common frames omitted
Caused by: java.lang.reflect.InvocationTargetException: null
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.7.0_80]
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) ~[na:1.7.0_80]
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.7.0_80]
        at java.lang.reflect.Constructor.newInstance(Constructor.java:526) ~[na:1.7.0_80]
        at org.hibernate.engine.internal.UnsavedValueFactory.instantiate(UnsavedValueFactory.java:46) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1]
        ... 43 common frames omitted
Caused by: java.lang.ClassCastException: sun.reflect.generics.reflectiveObjects.TypeVariableImpl cannot be cast to java.lang.Class
        at generic.models.GenericModel.<init>(GenericModel.java:51) ~[na:na]
        at myInsurance.models.Insurance.<init>(Insurance.java:151) ~[na:na]
        ... 48 common frames omitted

---

If it somehow helps, here is my previous post about Inheritance with Generics, which draws me to this issue.

Perhaps there is some issue with my contructors. I dont know, maybe I Should somewhere declare parameter typed constructor?

Please help me.

---

EDIT- Working solution

@MappedSuperclass
public abstract class GenericModel<T extends GenericModel> {
    /**
     * Works for nested/inner classes and Typed Parametered Classes
     */
    public GenericModel() {
        Class obtainedClass = getClass();
        Type genericSuperclass = null;
        for(;;) {
            genericSuperclass = obtainedClass.getGenericSuperclass();
            if(genericSuperclass instanceof ParameterizedType) {
                break;
            }
            obtainedClass = obtainedClass.getSuperclass();
        }
        ParameterizedType genericSuperclass_ = (ParameterizedType) genericSuperclass;
        try {
            entityClass = ((Class) ((Class) genericSuperclass_.getActualTypeArguments()[0]));
        } catch (ClassCastException e) {
            entityClass = guessEntityClassFromTypeParametersClassTypedArgument();
        }
    }
}   

---

/**
 * Use in case of extending GenericModel<ExtendingClass<TypeArgument>>
 * Use if passed into GenericModel TypeParameter which isn't actual class, but Class with TypedParameter
 * @return 
 */ 
public Class<T> guessEntityClassFromTypeParametersClassTypedArgument() {
    return ClassUtil.getActualTypeBinding(getClass(), GenericModel.class, 0);
}

---

package org.fastnate.data.util;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * Helper for inspection of classes.
 *
 * @author Tobias Liefke
 */
public final class ClassUtil {

    private static <I> Type getActualTypeArgument(final Class<? extends I> instanceClass, final Class<I> superClass,
            final int argumentIndex) {
        final List<Type> parents = new ArrayList<>();
        parents.add(instanceClass.getGenericSuperclass());
        parents.addAll(Arrays.asList(instanceClass.getGenericInterfaces()));
        for (final Type parentType : parents) {
            final Class<?> parentClass = parentType instanceof ParameterizedType ? (Class<?>) ((ParameterizedType) parentType)
                    .getRawType() : (Class<?>) parentType;

            // First check if we found the super class or interface
            if (superClass.equals(parentClass)) {
                // We found the requested super class - use the binding
                return ((ParameterizedType) parentType).getActualTypeArguments()[argumentIndex];
            } else if (parentClass != null && superClass.isAssignableFrom(parentClass)) {
                // Else step up
                final Type type = getActualTypeArgument(parentClass.asSubclass(superClass), superClass, argumentIndex);
                if (type instanceof Class) {
                    return type;
                } else if (type instanceof TypeVariable) {
                    return ((ParameterizedType) parentType).getActualTypeArguments()[Arrays.asList(
                            parentClass.getTypeParameters()).indexOf(type)];
                }
            }
        }

        return null;
    }

    /**
     * Resolves the actual binding of a generic type that was specified in a superclass and bound in a subclass.
     *
     * @param instanceClass
     *            the implementing class
     * @param superClass
     *            the superclass or interface which specifies the generic type variable
     * @param argumentIndex
     *            the index of the type variable in the superclass definition (0 = the first type variable)
     * @return the bound class for the variable in instanceClass
     */
    public static <T, I> Class<T> getActualTypeBinding(final Class<? extends I> instanceClass,
            final Class<I> superClass, final int argumentIndex) {
        Type type = getActualTypeArgument(instanceClass, superClass, argumentIndex);
        if (type instanceof TypeVariable<?>) {
            type = ((TypeVariable<?>) type).getBounds()[0];
        }
        if (type instanceof ParameterizedType) {
            type = ((ParameterizedType) type).getRawType();
        }
        if (type instanceof Class<?>) {
            return (Class<T>) type;
        }
        throw new NoSuchElementException("Can't find binding for the " + argumentIndex + ". argument of " + superClass
                + " in " + instanceClass);
    }

    private ClassUtil() {
        // Helper class
    }

}

Answer 1

This has nothing to do with JPA.

If you look at the stacktrace:

Caused by: java.lang.ClassCastException: 
    sun.reflect.generics.reflectiveObjects.TypeVariableImpl cannot be cast to java.lang.Class
        at generic.models.GenericModel.<init>(GenericModel.java:51) ~[na:na]

And it references this line:

entityClass = ((Class) ((Class) genericSuperclass_.getActualTypeArguments()[0]));

The actual type argument of Insurance ist not an explicit class, but a type variable. Sou you can't cast it to a class.

If you would like to find the actual binding for a parameter of your class - I've created that for Fastnate : ClassUtil.getActualTypeBinding :

ClassUtil.getActualTypeBinding(getClass(), GenericModel.class, 0);