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POUnable to get ID of newly-created JDO persistent entity using GAE/J DataNucleus plug-in version 2.1.2
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  1. POUnable to get ID of newly-created JDO persistent entity using GAE/J DataNucleus plug-in version 2.1.2
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    copied!<p><strong>My problem</strong></p> <p>I am porting my application from version 1.x to 2.0 of the DataNucleus plug-in for GAE/J using the new 1.7.5 GAE/J SDK. This changes my JDO version from 2.3 to 3.0.1. My persistent entity class has a primary key of type encoded string, along with read-only access to the object’s numeric ID. Each instance is the sole member of its entity group (children and parent are linked by numeric ID only).</p> <p>Previously, I have been able to create and persist a new <code>MyEntity</code> instance and then immediately access its numeric ID to store in the parent <code>MyEntity</code> instance’s list of child IDs.</p> <p>Now I find that the new instance’s numeric ID is not available immediately after persistence – even though it is generated and stored and is available later.</p> <p><strong>My question</strong></p> <p>Is there anything I can do to restore access to the numeric ID immediately following object creation and persistence?</p> <p><strong>"jdoconfig.xml" configuration extract</strong></p> <pre><code>&lt;persistence-manager-factory name="big-table"&gt; &lt;property name="javax.jdo.PersistenceManagerFactoryClass" value="org.datanucleus.api.jdo.JDOPersistenceManagerFactory" /&gt; &lt;property name="datanucleus.DetachAllOnCommit" value="true"/&gt; &lt;property name="javax.jdo.option.NontransactionalRead" value="true"/&gt; &lt;property name="javax.jdo.option.NontransactionalWrite" value="true"/&gt; &lt;property name="datanucleus.appengine.autoCreateDatastoreTxns" value="true" /&gt; [...] &lt;/persistence-manager-factory&gt; </code></pre> <p><strong>Persistent entity class code extract</strong></p> <pre><code>@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true") public class MyEntity implements Serializable { private static final long serialVersionUID = 1L; // No setter for this read-only data member @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String sEncodedKey; // No setter for this read-only data member @Persistent @Extension(vendorName="datanucleus", key="gae.pk-id", value="true") private Long loID; @Persistent private Long loParentID; // // Other persistent data members // public Long getID() { return loID; } // // Other getters and setters // } </code></pre> <p><strong>Persistence code including 3 logging points</strong></p> <pre><code>/** * Create a new entity. * @param loParentID * The ID of the entity, * a new child of which is to be created. * @param sChildName * The name of the new child to be created. * @return * The created entity child, * or &lt;code&gt;null&lt;/code&gt; if the operation was carried out unsuccessfully. */ public static MyEntity createEntityChild(Long loParentID, String sChildName) { MyEntity meResult = null; MyEntity mePersistedChild = null; PersistenceManagerFactory pmf = DataExchange.getPersistenceManagerFactory(); // My own method PersistenceManager pm = pmf.getPersistenceManager(); Transaction tx = pm.currentTransaction(); try { tx.begin(); MyEntity meChild = new MyEntity(); meChild.setParentID(loParentID); meChild.setName(sChildName); meChild.setActive(true); mePersistedChild = pm.makePersistent(meChild); // "Touch" data member not in the default fetch group ArrayList&lt;Long&gt; liChildIDs = mePersistedChild.getChildIDs(); if (liChildIDs != null) liChildIDs.size(); if (mePersistedChild != null) g_logger.log(Level.FINE, String.format( "Pre-commit: mePersistedChild.getID() = %d," + " mePersistedChild.getEncodedKey() = \"%s\".", mePersistedChild.getID(), mePersistedChild.getEncodedKey())); tx.commit(); if (mePersistedChild != null) g_logger.log(Level.FINE, String.format( "Post-commit: mePersistedChild.getID() = %d," + " mePersistedChild.getEncodedKey() = \"%s\".", mePersistedChild.getID(), mePersistedChild.getEncodedKey())); } finally { try { if (tx.isActive()) // Because of an exception, say tx.rollback(); } finally { pm.close(); } } if (mePersistedChild != null) g_logger.log(Level.FINE, String.format( "Post-pm-close: mePersistedChild.getID() = %d," + " mePersistedChild.getEncodedKey() = \"%s\".", mePersistedChild.getID(), mePersistedChild.getEncodedKey())); [...] return meResult; } </code></pre> <p><strong>Dev server logging output</strong></p> <pre><code>24-Feb-2013 13:28:02 [...].MyEntityBusiness createMyEntityChild FINE: Pre-commit: mePersistedChild.getID() = null, mePersistedChild.getEncodedKey() = "agttYXJrZXQtdHJlZXISCxIMSXRlbUNhdGVnb3J5GAUM". 24-Feb-2013 13:28:03 [...].MyEntityBusiness createMyEntityChild FINE: Post-commit: mePersistedChild.getID() = null, mePersistedChild.getEncodedKey() = "agttYXJrZXQtdHJlZXISCxIMSXRlbUNhdGVnb3J5GAUM". 24-Feb-2013 13:28:03 [...].MyEntityBusiness createMyEntityChild FINE: Post-pm-close: mePersistedChild.getID() = null, mePersistedChild.getEncodedKey() = "agttYXJrZXQtdHJlZXISCxIMSXRlbUNhdGVnb3J5GAUM". 24-Feb-2013 13:28:07 com.google.appengine.api.datastore.dev.LocalDatastoreService$PersistDatastore persist INFO: Time to persist datastore: 141 ms </code></pre> <p><strong>JDO enhancement version verification</strong></p> <p>The build process succeeded with output fragment:</p> <pre><code>datanucleusenhancer: 09:33:00,531 (main) INFO [DataNucleus.Enhancer] - DataNucleus Enhancer for API "JDO" 09:33:01,125 (main) INFO [DataNucleus.Enhancer] - DataNucleus Enhancer (version 3.1.1) : Enhancement of classes DataNucleus Enhancer (version 3.1.1) : Enhancement of classes 09:33:03,281 (main) INFO [DataNucleus.Enhancer] - Writing class file "[Path]\MyEntity.class" with enhanced definition [... (N entries in all)] 09:33:04,046 (main) INFO [DataNucleus.Enhancer] - DataNucleus Enhancer completed with success for [N] classes. Timings : input=1922 ms, enhance=984 ms, total=2906 ms. Consult the log for full details DataNucleus Enhancer completed with success for [N] classes. Timings : input=1922 ms, enhance=984 ms, total=2906 ms. Consult the log for full details </code></pre> <p><strong>Software environment</strong></p> <ul> <li>Web server: Google App Engine for Java version 1.7.5</li> <li>Web framework: Apache Wicket 6.5.0</li> <li>Java version: 1.6.0_39; Java HotSpot(TM) Client VM 20.14-b01</li> <li>GAE/J DataNucleus plug-in version: 2.1.2</li> <li>DataNucleus Access Platform version: 3.1.3</li> <li>JDO version: 3.0.1</li> <li>Operating system: Microsoft Windows XP version 5.1 running on x86</li> <li>IDE: NetBeans 7.2 (build 201207171143)</li> </ul>
 

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