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POHibernate with user defined IdentifierGenerator UUID
 

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    <p>I am working with a environment using Hibernate 3.6. I am trying to implement a MySQL table that uses UUIDs from java.util as the PK, these UUIDs are generated from multiple Strings defined by the EntityImage. Here is the code I am using to generate those keys.</p> <pre><code>public class EntityIDGenerator implements IdentifierGenerator { ... private UUID generateUUID(String str) { return UUID.nameUUIDFromBytes(str.getBytes()); } public UUID generateUUID(EntityImage image) { return generateUUID(image.getEntityId()+image.getEntityType().toUpperCase()+image.getFilename().toUpperCase()); } ... public Serializable generate(SessionImplementor session, Object object) throws HibernateException { if(object instanceof EntityImage) { return generateUUID((EntityImage)object); } return null; } } </code></pre> <p>and here his my hibernate</p> <pre><code>&lt;class name="EntityImage" table="entity_image"&gt; &lt;id name="id" column="id" type="entityUUID" unsaved-value="null"&gt; &lt;generator class="com.covelo.energy.score.db.EntityIDGenerator" /&gt; &lt;/id&gt; &lt;property name="entityId" type="int"/&gt; &lt;property name="entityType" type="string" length="45" /&gt; &lt;property name="filename" type="string" length="90" /&gt; &lt;property name="fileType" type="string" length="5"/&gt; &lt;property name="imageData" type="binary" column="image_data"/&gt; &lt;/class&gt; </code></pre> <p>With my current setup I can only get it to work one way, generate the UUID myself and check if a key exists in the Hibernate then call a save or update accordingly (or just set the UUID to null or the value respectively)</p> <p>This way seems wrong especially for having this PK generator implemented. Ideally Hibernate would generate a PK using my IdentifierGenerator then check if it exists and update or save it. Am I going about my architecture wrong or is there a method to do this in hibernate?</p> <p><strong>Note:</strong> I am well aware of how saveOrUpdate works <a href="http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/objectstate.html#objectstate-saveorupdate" rel="nofollow">Hibernate documentation</a></p> <p>-Thanks in advance. Ned</p>
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    1. COThis doesn't make much sense. An ID generator is used to generate IDs for new entities being inserted in the database. It should always generate a non-existing ID. If an entity must be updated, then it must already have an ID, and no ID should thus be generated.
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    2. COHello JB Niznet, I understand that that I trying am using the ID generator in a unconventional way, is there a method to use hibernate in the fashion that I am describing other than an implementing an IdentifierGenerator?
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    3. COMy point is precisely that this shouldn't be done by implementing an ID generator. I don't see the point in generating an ID for an entity that already exists. If you want to check if an entity identified by something other than its ID (file name, etc.) already exists, then that's business logic code, that you should implement in your business services.
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