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Date: Wed, 08 Oct 2008 10:32:31 -0700
Subject: Re: How to annotate a positional List
From: Kevin Cox <kc6522@att.com>
To: <users@openjpa.apache.org>
Message-ID: <C5123CBF.10161%kc6522@att.com>
Thread-Topic: How to annotate a positional List
Thread-Index: Ackpa9d4G2ifd/miqkK589oO/zvXXw==
In-Reply-To: <gcilvv$qfs$1@ger.gmane.org>
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Andy, thanks for you input.
I am trying your last solution.  The actual classes are shown below.  The DB
is oracle 10g.  I am running the test using the following code to create a
book then looking up the book and trying to add a couple pages.  The SQL
generate is exactly as you suspected and shown below.  I get an Optimistic
locking error when trying to commit the updates (added pages).  Do you see
what might be wrong?

//First, just create a book and a couple pages - works fine
EntityManager em = MyPersistence.getInstance().createEntityManager();
em.getTransaction().begin();

PageOfBook p1 = new PageOfBook();
p1.setData("This is a page 1 in a book");

PageOfBook p2 = new PageOfBook();
p2.setData("This is a page 2 in a book");

Book b = new Book("My Book Example for Lists");
b.getPages().add(p1);
b.getPages().add(p2);

em.persist(b);
em.getTransaction().commit();

//WORKS GREAT UP TO HERE - RECORDS GET WRITTEN TO DB AND OrderColumn is
creating a numbered sequence!

//Now, I am testing if I can add to the list, look up the saved book
em.getTransaction().begin();
//Query q3 = em.createQuery("SELECT book from Book book where book.id =
?1");
//q3.setParameter(1,1L);
//Book book = (Book) q3.getSingleResult();
BOTH THE QUERY AND THE EM.FIND RESULT IN Optimistic locking error exception

Book book = em.find(Book.class, 1L);

PageOfBook p3 = new PageOfBook();
p3.setData("This is a page 3 in a book");
PageOfBook p4 = new PageOfBook();
p3.setData("This is a page 4 in a book");
book.getPages().add(p3);
book.getPages().add(p4);

em.getTransaction().commit();
//on this commit, I get
Exception in thread "main" <openjpa-1.2.0-r422266:683325 fatal store error>
org.apache.openjpa.persistence.RollbackException: Optimistic locking errors
were detected when flushing to the data store.  The following objects may
have been concurrently modified in another transaction:
[com.play.cmsdata.PageOfBook@5f55b990, com.play.cmsdata.PageOfBook@4319b06e]
    at 
org.apache.openjpa.persistence.EntityManagerImpl.commit(EntityManagerImpl.ja
va:523)
    at hellojpa.Main.createBook(Main.java:122)
    at hellojpa.Main.main(Main.java:37)
Caused by: <openjpa-1.2.0-r422266:683325 nonfatal store error>
org.apache.openjpa.persistence.OptimisticLockException: Optimistic locking
errors were detected when flushing to the data store.  The following objects
may have been concurrently modified in another transaction:
[com.play.cmsdata.PageOfBook@5f55b990, com.play.cmsdata.PageOfBook@4319b06e]
    at 
org.apache.openjpa.kernel.BrokerImpl.newFlushException(BrokerImpl.java:2160)
    at org.apache.openjpa.kernel.BrokerImpl.flush(BrokerImpl.java:2010)
    at org.apache.openjpa.kernel.BrokerImpl.flushSafe(BrokerImpl.java:1908)
    at 
org.apache.openjpa.kernel.BrokerImpl.beforeCompletion(BrokerImpl.java:1826)
    at 
org.apache.openjpa.kernel.LocalManagedRuntime.commit(LocalManagedRuntime.jav
a:81)
    at org.apache.openjpa.kernel.BrokerImpl.commit(BrokerImpl.java:1350)
    at 
org.apache.openjpa.kernel.DelegatingBroker.commit(DelegatingBroker.java:877)
    at 
org.apache.openjpa.persistence.EntityManagerImpl.commit(EntityManagerImpl.ja
va:512)
    ... 2 more
Caused by: <openjpa-1.2.0-r422266:683325 nonfatal store error>
org.apache.openjpa.persistence.OptimisticLockException: An optimistic lock
violation was detected when flushing object instance
"com.play.cmsdata.PageOfBook@5f55b990" to the data store.  This indicates
that the object was concurrently modified in another transaction.
FailedObject: com.play.cmsdata.PageOfBook@5f55b990

em.close();


-----------------------------------------------------------
import org.apache.openjpa.persistence.jdbc.OrderColumn;
import org.apache.openjpa.persistence.PersistentCollection;

import javax.persistence.*;
import java.util.List;
import java.util.ArrayList;

@Entity
@SequenceGenerator(name="BookSeq", sequenceName="BOOK_SEQ")
public class Book {
   @Id @GeneratedValue(strategy= GenerationType.TABLE, generator="BookSeq")
   private long id;

   String title;

   @PersistentCollection(elementCascade=CascadeType.ALL)
   @OrderColumn
   private List<PageOfBook> pages = new ArrayList<PageOfBook>();

    public Book() {
    }

    public Book(long id) {
        this.id = id;
    }

    public Book(String title) {
        this.title = title;
    }

    public long getId() {
        return id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public List<PageOfBook> getPages() {
        return pages;
    }

    public void setPages(List<PageOfBook> pages) {
        this.pages = pages;
    }
}


-----------------------------------------------------------
import javax.persistence.*;
import javax.persistence.Lob;
import javax.persistence.GeneratedValue;

@Entity
@SequenceGenerator(name="PageOfBookSeq", sequenceName="PAGEOFBOOK_SEQ")
public class PageOfBook {
   @Id @GeneratedValue(strategy= GenerationType.TABLE,
generator="PageOfBookSeq")
   private long id;

   @Lob
   private String data;

    public PageOfBook() {
    }

    public long getId() {
        return id;
    }

    public String getData() {
        return data;
    }

    public void setData(String data) {
        this.data = data;
    }
}


Here are the actual generated tables (from sql trace):
CREATE TABLE Book (id NUMBER NOT NULL, title VARCHAR2(255), PRIMARY KEY
(id))
CREATE TABLE Book_PageOfBook (BOOK_ID NUMBER, PAGES_ID NUMBER, ordr NUMBER)
CREATE TABLE PageOfBook (id NUMBER NOT NULL, data CLOB, PRIMARY KEY (id))