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How do you map a collection of objects of a base type in a derived type of the same inheritance tree?

Background

The object model is such that:

  • A “component” is primitive; it cannot be made up of smaller parts.
  • A 'Part' is composite. It may consist of “Components”, other “parts”, or any combination of the two.

I modeled this by inheriting a part from Component, and then Part has a collection of Component objects that it consists of.

Assumptions

  • Java 1.6
  • Hibernate 3.5.1-final
  • Display HBM files (vs Annotations)

Problem

When I try to create a Part object, I get an integrity constraint violation:

14:29:24,121  WARN JDBCExceptionReporter:100 - SQL Error: -177, SQLState: 23503
14:29:24,126 ERROR JDBCExceptionReporter:101 - integrity constraint violation: foreign key no parent; FK24013CDD89C7219B table: COMPONENT

Looking at the circuit that hbm2ddl creates below, it looks like it creates an impossible situation.

FK Inheritance

Part FK PartID- > ComponentID - , .

alter table Part add constraint FK25D813296E407B foreign key (PartID) references Component;

FK

Component Part FK ComponentID . , , .

alter table Component add constraint FK24013CDD89C7219B foreign key (ComponentID) references Part;

, , :

alter table Component add constraint FK24013CDD89C7219B foreign key (PartID) references Part;


alter table <Name of class in the collection> add constraint FK123 foreign key (id of the class object which owns the collection) references (Name of the class that holds the collection)

, ComponentID, , PartID FK'd ComponentID - . , , FK , .

?

Java POJO

package manufacturing;

public class Component {
    private long _id;
    private String _name;
    private float _price;

    // Hibernate requires all persistent classes to have a default constructor, even if it is private.
    @SuppressWarnings("unused")
    protected Component() {
        this(-1L, "", 0.0f);
    }

    public Component(String name) {
        this(-1L, name, 0.0f);
    }

    public Component(long id, String name, float price) {
        setID(id);
        setName(name);
        setPrice(price);
    }

    public long getID() {
        return _id;
    }

    // Required method for Hibernate
    protected void setID(long id) {
        _id = id;
    }


    public String getName() {
        return _name;
    }

    public void setName(String name) {
       _name = name;
    }

    public float getPrice() {
        return _price;
    }

    public void setPrice(float price) {
        _price = price;
    }
}


package manufacturing;

import java.util.Collection;
import java.util.HashSet;

public class Part extends Component {
    private Collection<Component> _subcomponents;

    // Hibernate requires all persistent classes to have a default constructor, even if it is private.
    @SuppressWarnings("unused")
    private Part() {
        this(-1L, "", 0.0f, new HashSet<Component>());
    }

    public Part(String name) {
        this(-1L, name, 0.0f, new HashSet<Component>());
    }

    public Part(long id, String name, float price, Collection<Component> subcomponents) {
        super(id, name, price);
        setSubcomponents(subcomponents);
    }

    public Collection<Component> getSubcomponents() {
        return _subcomponents;
    }

    public void setSubcomponents(Collection<Component> subcomponents) {
        _subcomponents = subcomponents;
    }

}


<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
                        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
                        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="manufacturing">
 <class name="Component" table="Component">
  <id name="ID" column="ComponentID">
   <generator class="native" />
  </id>
  <property name="name" column="Name" />
  <property name="price" column="Price" />        

  <joined-subclass name="Part" table="Part">
   <key column="PartID" />
   <!-- A part has has [0..n] subcomponents -->
   <set name="Subcomponents" lazy="true" cascade="all" inverse="true">
    <key column="ComponentID" />
    <one-to-many class="Component" />
   </set>

  </joined-subclass>
 </class>
</hibernate-mapping>

HBM2DDL

create table Component (ComponentID bigint generated by default as identity (start with 1), Name varchar(255), Price float, primary key (ComponentID));
create table Part (PartID bigint not null, primary key (PartID));
alter table Component add constraint FK24013CDD89C7219B foreign key (ComponentID) references Part;
alter table Part add constraint FK25D813296E407B foreign key (PartID) references Component;

Relavent Stack

14:28:15,001 DEBUG SessionImpl:257 - opened session at timestamp: 12798232950
14:28:47,299 DEBUG JDBCTransaction:82 - begin
14:28:47,313 DEBUG ConnectionManager:444 - opening JDBC connection
14:28:47,333 DEBUG JDBCTransaction:87 - current autocommit status: false
14:29:23,929 DEBUG AbstractSaveEventListener:320 - executing identity-insert immediately
14:29:23,941 DEBUG AbstractBatcher:410 - about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
14:29:23,948 DEBUG SQL:111 - insert into Component (ComponentID, Name, Price) values (null, ?, ?)
Hibernate: insert into Component (ComponentID, Name, Price) values (null, ?, ?)
14:29:23,966 DEBUG AbstractBatcher:418 - about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
14:29:23,991 DEBUG JDBCExceptionReporter:92 - could not insert: [manufacturing.Part] [insert into Component (ComponentID, Name, Price) values (null, ?, ?)]
java.sql.SQLException: integrity constraint violation: foreign key no parent; FK24013CDD89C7219B table: COMPONENT
 at org.hsqldb.jdbc.Util.sqlException(Unknown Source)
 at org.hsqldb.jdbc.JDBCPreparedStatement.fetchResult(Unknown Source)
 at org.hsqldb.jdbc.JDBCPreparedStatement.executeUpdate(Unknown Source)
 at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94)
 at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57)
 at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2329)
 at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2836)
 at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
 at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:268)
 at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321)
 at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
 at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)
 at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
 at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
 at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
 at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
 at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
 at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:705)
 at org.hibernate.impl.SessionImpl.save(SessionImpl.java:693)
 at org.hibernate.impl.SessionImpl.save(SessionImpl.java:689)
 at DAO.GenericHibernateDAO.create(GenericHibernateDAO.java:91)
 at DAO.PartDAOHibernateTest.testCreatePartWithNoSubcomponents(PartDAOHibernateTest.java:69)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
 at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
 at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
 at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
 at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
 at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
 at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
 at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
 at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
 at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
 at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
 at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
 at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
 at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
 at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
 at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
 at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
 at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:49)
 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)
14:29:24,121  WARN JDBCExceptionReporter:100 - SQL Error: -177, SQLState: 23503
14:29:24,126 ERROR JDBCExceptionReporter:101 - integrity constraint violation: foreign key no parent; FK24013CDD89C7219B table: COMPONENT
+3
1

: .

, , , . , , , , . - , Part - , . Component , Part - .

№ 1 -

Part, ComponentID, PartID. Hibernate Reference Documentation 6.2.1. :

, .

, Part - , , PartID .

№2 -

Hibernate - inverse = true

, . , inverse = "false" ( ) SQL-. , inverse = "true", .

, , , Part inverse = "false" ( , false). false true, PartID Component , , . , , , Hibernate, .

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
                        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
                        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="manufacturing">
    <class name="Component" table="Component">
        <id name="ID" column="ComponentID">
            <generator class="native" />
        </id>
        <property name="name" column="Name" />
        <property name="price" column="Price" />        

        <joined-subclass name="Part" table="Part">
            <key column="PartID" />
            <!-- A part has has [0..n] sub-components -->
            <set name="Subcomponents" lazy="true" cascade="all" inverse="false">
                <key column="PartID" />
                <one-to-many class="Component" />
            </set>

        </joined-subclass>
    </class>
</hibernate-mapping>

:

create table Component (ComponentID bigint generated by default as identity (start with 1), Name varchar(255), Price float, PartID bigint, primary key (ComponentID));
create table Part (PartID bigint not null, primary key (PartID));
alter table Component add constraint FK24013CDD89368311 foreign key (PartID) references Part;
alter table Part add constraint FK25D813296E407B foreign key (PartID) references Component;
+1

Source: https://habr.com/ru/post/1756048/

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