replicate() with a bidirectional relationship fails (dom4j)

tash · **Joined:** Sun Jun 27, 2004 5:05 pm **Posts:** 11

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Basically, I'm trying to use the dom4j session to create a data transfer between databases. So, I have an extractor that creates an XML document from a database, and then a have a populator that takes the XML document and replicates() objects in an empty DB.

This works great, except for when I try to populate a pair of classes that have a bidirectional relationship (one-to-many and many-to-one). I get a "java.sql.SQLException: Cannot add or update a child row: a foreign key constraint fails" error message.

Am I going about this the wrong way? Should I be using something besides replicate()?

Hibernate version:
3.0.5

Mapping documents:

Code:

<hibernate-mapping
    package="data">
    <class name="Foo"
           table="foo"
           >
        <id name="id"
            node="@id"
            type="string"
            unsaved-value="null"
            column="foo_id" >
            <generator class="uuid" />
        </id>
        <property
            name="prop1"
            column="prop1"
            type="string"
            />
        <many-to-one
            name="bar"
            column="bar_id"
            class="Bar"
            not-null="false"
            embed-xml="false"
            />
        <property
            name="index"
            column="foo_index"
            type="int"
            update="true"
            />
     </class>
    <class name="Bar"
           table="bar"
           >
        <id name="id"
            node="@id"
            type="string"
            unsaved-value="null"
            column="bar_id" >
            <generator class="uuid" />
        </id>
        <list
            name="foos"
            node="foos"
            embed-xml="true"
            inverse="true"
            lazy="false">
            <key column="bar_id"/>
            <list-index column="foo_index"/>
            <one-to-many
                class="Foo"
                embed-xml="false"
                node="foo"
                />
        </list>
    </class>
</hibernate-mapping>

Code between sessionFactory.openSession() and session.close():
Here is the populator:

Code:

        try
        {
            SAXReader reader = new SAXReader();
            Document doc = reader.read(new File("content.xml"));

            Session session = currentSession();
            Session s = session.getSession(EntityMode.DOM4J);
            Transaction txn = s.beginTransaction();
            {
                List elems = doc.getRootElement().elements();
                Iterator it = elems.iterator();
                while(it.hasNext())
                {
                    Element e = (Element)it.next();
                    log.debug(e.getName());
                    if(e.getName().equals("Foo"))
                        s.replicate("data.Foo",e, ReplicationMode.IGNORE);
                    if(e.getName().equals("Bar"))
                        s.replicate("data.Bar",e, ReplicationMode.IGNORE);
                }
            }

            txn.commit();
        }
        catch(DocumentException e)
        {
            log.error(e);
        }

Full stack trace of any exception that occurs:
150 [main] ERROR org.hibernate.util.JDBCExceptionReporter - Cannot add or update a child row: a foreign key constraint fails
291 [main] ERROR org.hibernate.event.def.AbstractFlushingEventListener - Could not synchronize database state with session
org.hibernate.exception.ConstraintViolationException: could not insert: [data.Foo]
at org.hibernate.exception.ErrorCodeConverter.convert(ErrorCodeConverter.java:74)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.persister.entity.BasicEntityPersister.insert(BasicEntityPersister.java:1869)
at org.hibernate.persister.entity.BasicEntityPersister.insert(BasicEntityPersister.java:2200)
at org.hibernate.action.EntityInsertAction.execute(EntityInsertAction.java:46)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:239)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:223)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:136)
at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:274)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:27)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:730)
at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:329)
at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:86)
at Test.reconstitute(Test.java:69)
at Test.main(Test.java:40)
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:585)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:78)
Caused by: java.sql.SQLException: Cannot add or update a child row: a foreign key constraint fails
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2851)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1531)
at com.mysql.jdbc.ServerPreparedStatement.serverExecute(ServerPreparedStatement.java:1366)
at com.mysql.jdbc.ServerPreparedStatement.executeInternal(ServerPreparedStatement.java:952)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1974)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1897)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1758)
at org.hibernate.jdbc.NonBatchingBatcher.addToBatch(NonBatchingBatcher.java:22)
at org.hibernate.persister.entity.BasicEntityPersister.insert(BasicEntityPersister.java:1853)
... 17 more
Exception in thread "main" org.hibernate.exception.ConstraintViolationException: could not insert: [data.Foo]
at org.hibernate.exception.ErrorCodeConverter.convert(ErrorCodeConverter.java:74)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.persister.entity.BasicEntityPersister.insert(BasicEntityPersister.java:1869)
at org.hibernate.persister.entity.BasicEntityPersister.insert(BasicEntityPersister.java:2200)
at org.hibernate.action.EntityInsertAction.execute(EntityInsertAction.java:46)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:239)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:223)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:136)
at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:274)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:27)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:730)
at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:329)
at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:86)
at Test.reconstitute(Test.java:69)
at Test.main(Test.java:40)
Name and version of the database you are using:
MySQL 4.1.12

The generated SQL (show_sql=true):
0 [main] DEBUG Test - Creating new Hibernate Session: main
10 [main] DEBUG Test - Foo
Hibernate: select foo_id from foo where foo_id =?
70 [main] DEBUG Test - Foo
Hibernate: select foo_id from foo where foo_id =?
70 [main] DEBUG Test - Bar
Hibernate: select bar_id from bar where bar_id =?
Hibernate: insert into foo (prop1, bar_id, foo_index, foo_id) values (?, ?, ?, ?)

-----------
The content.xml document looks like this:

Code:

<root>
  <Foo id="402881e4045ce90c01045ce90f950002">
    <prop1>abcd</prop1>
    <bar>402881e4045ce90c01045ce90f770001</bar>
    <index>0</index>
  </Foo>
  <Foo id="402881e4045ce90c01045ce90f9f0003">
    <prop1>456</prop1>
    <bar>402881e4045ce90c01045ce90f770001</bar>
    <index>1</index>
  </Foo>
  <Bar id="402881e4045ce90c01045ce90f770001">
    <foos>
      <foo>402881e4045ce90c01045ce90f950002</foo>
      <foo>402881e4045ce90c01045ce90f9f0003</foo>
    </foos>
  </Bar>
</root>

It was created using this:

Code:

    private static void createDocument() {
        Session sess;
        sess = currentSession();
        Session s = sess.getSession(EntityMode.DOM4J);

        Document doc = DocumentHelper.createDocument();
        Element root = doc.addElement("root");

        List results = s.createQuery("from Foo foo ").list();
        addResultsToNode(results, root);

        results = s.createQuery("from Bar bar ").list();
        addResultsToNode(results, root);

        OutputFormat format = OutputFormat.createPrettyPrint();
        try
        {
            XMLWriter writer = new XMLWriter(new FileWriter("content.xml"), format);
            writer.write(doc);
            writer.close();
        }  catch(IOException ioe) {    }

    }

    private static void addResultsToNode(List results, Element root)
    {
        for (Iterator i = results.iterator(); i.hasNext();) {
            Element e = (Element) i.next();
            if(e != null)
            {
                log.debug("e: "+e.toString());
                root.add(e);
            }
        }
    }

jkuipers · **Joined:** Thu Jun 02, 2005 5:09 am **Posts:** 22

AFAIK, bi-directional List associations aren't supported when using inverse="true" on the parent-side: Hibernate will ignore changes made only to the collection, so re-ordening of your collection elements won't result in updates of the index column of the row representing these elements.
I did see two pages mentioning new support for these kind of relations in Hibernate 3, but I have some questions about this support myself (see http://forum.hibernate.org/viewtopic.php?t=943384, the text also refers to the two relevant pages on the Hibernate site).

Joris

tash · **Joined:** Sun Jun 27, 2004 5:05 pm **Posts:** 11

Hmmm, good idea, but removing inverse="true" didn't seem to have any effect.

I really think there is an issue in the dom4j session.replicate() - it's not a problem just save()ing objects - it's the replication that gets messed up. (I would think that it it verifying foreign keys that aren't there yet).

-Dave

kilon4572 · **Joined:** Fri Mar 04, 2005 9:33 pm **Posts:** 3

I think you cant have the inverse like his suggestion as this would form a curcular reference which i think still an xml paradox when redering a bidirectional relation in other words try without a biderectional

harickson · **Joined:** Mon Aug 02, 2010 3:11 am **Posts:** 1

hmm.... really good idea but as the Mr. tash you have to remore "true" from this. and after this it may be goona useful to you.

Thanks!!!