Hibernate: Getting org.hibernate.InstantiationException While Fetching polymorphic Collections in onetomany association

Question

I am trying to use JOINED inheritance strategy in Hibernate using JPA annotations. My Base class is abstract and have Many to One association with other entities. However I am getting Hibernate Exception: Cannot instantiate abstract class or interface. Following is my class structure:

Account.java

@Entity(name="BANK_ACCOUNTS")
@Inheritance(strategy=InheritanceType.JOINED)
public abstract class Account {

    @Id
    @Column(name="ACC_ID")
    @SequenceGenerator(name="account_id_seq", sequenceName="BANK_ACCOUNT_ACC_ID", allocationSize=1)
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="account_id_seq")
    private Long id;

    @Column(name="IS_ACTIVE")
    @Type(type="yes_no")
    private Boolean isActive;

    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="ACC_BRANCH_ID")
    private Branch branch;
}

SavingsAccount.java

@Entity(name="BANK_SAVINGS_ACCOUNT")
public class SavingsAccount extends Account{

    @Column(name="CURR_BAL")
    private BigDecimal currentBalance;
}

Branch.class

@Entity(name="BANK_BRANCH")
public class Branch {

    @Id
    @Column(name="BRANCH_ID")
    @SequenceGenerator(name="branch_id_seq", sequenceName="BANK_BRANCH_BRANCH_ID", allocationSize=1)
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="branch_id_seq")
    private Long id;


    @OneToMany(mappedBy="branch",orphanRemoval=true, fetch= FetchType.LAZY)
    @Cascade(value=org.hibernate.annotations.CascadeType.ALL)
    private Set<Account> accounts = new HashSet<Account>(); 
}

So whenever I try to get list of accounts held by branch using the following code I get the exception mentioned below:

Branch branch = (Branch) session.get(Branch.class, branchId);
SavingsAccount acc = new SavingsAccount();
acc.setBranch(branch);
branch.getAccounts().add(acc);

Exception trace:

org.hibernate.InstantiationException: Cannot instantiate abstract class or interface:  : com.sapient.bank.entities.Account
    at org.hibernate.tuple.PojoInstantiator.instantiate(PojoInstantiator.java:114)
    at org.hibernate.tuple.PojoInstantiator.instantiate(PojoInstantiator.java:136)
    at org.hibernate.tuple.entity.AbstractEntityTuplizer.instantiate(AbstractEntityTuplizer.java:737)
    at org.hibernate.persister.entity.AbstractEntityPersister.instantiate(AbstractEntityPersister.java:4761)
    at org.hibernate.internal.SessionImpl.instantiate(SessionImpl.java:1427)
    at org.hibernate.internal.SessionImpl.instantiate(SessionImpl.java:1415)
    at org.hibernate.loader.plan.exec.process.internal.EntityReferenceInitializerImpl.hydrateEntityState(EntityReferenceInitializerImpl.java:235)
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.readRow(AbstractRowReader.java:107)
    at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:129)
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:138)
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:102)
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:100)
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:693)
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:92)
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:1933)
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:559)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:261)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:555)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:143)
    at org.hibernate.collection.internal.AbstractPersistentCollection$3.doWork(AbstractPersistentCollection.java:336)
    at org.hibernate.collection.internal.AbstractPersistentCollection$3.doWork(AbstractPersistentCollection.java:324)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:261)
    at org.hibernate.collection.internal.AbstractPersistentCollection.readElementExistence(AbstractPersistentCollection.java:323)
    at org.hibernate.collection.internal.PersistentSet.add(PersistentSet.java:200)
    at com.sapient.bank.dao.AccountDao.createNewSavingsAcc(AccountDao.java:28)
    at com.sapient.util.MainClass.main(MainClass.java:32)

Please help me understand what is wrong with my code. Its working fine if I remove abstract keyword, but I want to make Account class as abstract. Is there any way to achieve this?

Answer 1

You could try for the following syntax in Branch Entity if you would like allow SavingsAccount or Child of SavingsAccount:

 @Cascade(value=org.hibernate.annotations.CascadeType.ALL)
 private Set<? extends Account> accounts = new HashSet<SavingsAccount>(); 

If you would like to add all future Sub Object of Account, then

 @Cascade(value=org.hibernate.annotations.CascadeType.ALL)
     private Set<? extends Account> accounts = new HashSet<Account>();

Answer 2

You should make the Account class a MappedSuperclass instead of an Entity. I didn't try it, so let me know, but that's how you deal with abstract classes with JPA annotations.

Reference: The Java EE 6 Tutorial : Entity Inheritance