custom IdentifierGenerator, trying to embed native Generator

danny_mandel · **Posted:** Wed Jul 14, 2004 12:21 am

Hi all. First off let me say thanks for such a kickass product! I really love using Hibernate and I don't think I can ever go back to scattered SQL!

Relevant platform details:
Hibernate 2.1.2
Spring 1.0.1
jdk1.4.2
MySQL 4.0.16-standard

I'm having a problem with a custom identifier generator. I'm attempting to embed a native generator inside my custom generator so that most of the time the native generator gets called. There are, however, cases where I would like to use a pre-existing identifier (when I'm copying between different databases). The way I'm attemping to do this is by creating a native id generator (via a call to net.sf.hibernate.id.IdentifierGeneratorFactory) in the constructor of my custom IdentifierGenerator class. I want to use this native generator at all times except for the special case of copying between databases (and keeping the identifier consistent across multiple databases). However, when I attempt to use this native generator, I'm getting a MySQL driver error:

Code:

java.sql.SQLException: SQL String can not be NULL

.

I guess my questions are:
1) Is this possible, or do I need to think of another way to maintain ids between databases
2) If it is possible, what am I doing wrong?

The hibernate (spring) code is very simple -- I should mention that it works when I use a native id generator:

Code:

   public void addAccessoryPage(MappedAccessoryPage page) {
      getHibernateTemplate().save(page);
        }

The generator is as follows:

Code:

public class PossiblyExistingIdGenerator implements IdentifierGenerator {
   /**
    * Use an IdentityGenerator if things are not set to be copied
    */
   private IdentifierGenerator hibernateGenerator;
   
   public PossiblyExistingIdGenerator() {
      System.out.println("PossiblyExistingIdGenerator getting constructed \n\n");
      try {
                        // Construction of native generator
         hibernateGenerator = IdentifierGeneratorFactory.create("native", new LongType(), null, new MySQLDialect());
         System.out.println("generator's class is: " + hibernateGenerator);
      } catch (Exception e) {
         e.printStackTrace();
      }
   }
   
   public synchronized Serializable generate(SessionImplementor session, Object object) {
      if (object instanceof PersistentCopyable && ((PersistentCopyable) object).getCopiedIdentifier() != null) {
         Long id = ((PersistentCopyable) object).getCopiedIdentifier();
         System.out.println(" going to return: " + id); 
         return id;    
      } else {
         try {
            System.out.println(" going to call identity generator to generate new id ");
                                // Usage of native generator -- happens in most cases
            Serializable returnValue = hibernateGenerator.generate(session, object);
            System.out.println(" identity generator generated: " + returnValue);
            return returnValue;
         } catch (Exception e) {
            e.printStackTrace();
            return null;
         }
      }
   }
}

My mapping document is as follows:

Code:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 2.0//EN" 
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>
    <class
        name="org.tolweb.hibernate.MappedAccessoryPage"
        table="ACCESSORY_PAGES"
        dynamic-update="false"
        dynamic-insert="false"
    >

        <id
            name="accessoryPageId"
            column="id"
            type="java.lang.Long"
            unsaved-value="null"
        >
            <generator class="org.tolweb.hibernate.PossiblyExistingIdGenerator">
            </generator>
        </id>

        <property
            name="isSubmitted"
            type="boolean"
            update="true"
            insert="true"
            access="property"
            column="is_submitted"
        />

        <property
            name="isTreehouse"
            type="boolean"
            update="true"
            insert="true"
            access="property"
            column="is_treehouse"
        />

        <property
            name="menu"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="menu"
        />

        <property
            name="pageTitle"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="page_title"
        />

        <property
            name="copyright"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="page_copyrightholder"
        />

        <property
            name="copyrightYear"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="page_copyrightdate"
        />

        <property
            name="text"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="main_text"
        />

        <property
            name="references"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="refs"
        />

        <property
            name="status"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="status"
        />

        <property
            name="useContent"
            type="boolean"
            update="true"
            insert="true"
            access="property"
            column="use_content"
        />

        <set
            name="contributors"
            table="ACC_PAGE_CONTRIBUTORS"
            lazy="false"
            inverse="false"
            cascade="none"
            sort="natural"
            order-by="page_order asc"
        >

              <key
                  column="page_id"
              >
              </key>

              <composite-element
                  class="org.tolweb.treegrow.page.AccessoryPageContributor"
              >

        <property
            name="order"
            type="int"
            update="true"
            insert="true"
            access="property"
            column="page_order"
        />

        <property
            name="contributorId"
            type="int"
            update="true"
            insert="true"
            access="property"
            column="contributor_id"
        />

        <property
            name="isAuthor"
            type="boolean"
            update="true"
            insert="true"
            access="property"
            column="is_author"
        />

        <property
            name="isContact"
            type="boolean"
            update="true"
            insert="true"
            access="property"
            column="is_contact"
        />

        <property
            name="isCopyOwner"
            type="boolean"
            update="true"
            insert="true"
            access="property"
            column="is_copy_owner"
        />

              </composite-element>

        </set>

        <set
            name="internetLinks"
            table="InternetLinks"
            lazy="false"
            inverse="false"
            cascade="none"
            sort="natural"
            order-by="link_order asc"
        >

              <key
                  column="acc_page_id"
              >
              </key>

              <composite-element
                  class="org.tolweb.treegrow.page.InternetLink"
              >
        <property
            name="order"
            type="int"
            update="true"
            insert="true"
            access="property"
            column="link_order"
        />

        <property
            name="comments"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="comments"
        />

        <property
            name="siteName"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="siteName"
        />

        <property
            name="url"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="url"
        />

              </composite-element>

        </set>

        <set
            name="nodesSet"
            table="Acc_Pages_To_Nodes"
            lazy="false"
            inverse="false"
            cascade="none"
            sort="unsorted"
        >

              <key
                  column="acc_page_id"
              >
              </key>

              <many-to-many
                  class="org.tolweb.hibernate.MappedNode"
                  column="node_id"
                  outer-join="auto"
               />
        </set>
        <property
            name="contributorId"
            type="int"
            update="true"
            insert="true"
            access="property"
            column="contributor_id"
        />
        <property
            name="usePermission"
            type="byte"
            update="true"
            insert="true"
            access="property"
            column="use_permission"
        />
        <property
            name="acknowledgements"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="acknowledgements"
        />
        <property
            name="notes"
            type="java.lang.String"
            update="true"
            insert="true"
            access="property"
            column="notes"
        />
    </class>
</hibernate-mapping>

Here's a more detailed debug log:

Code:

34:33,322 DEBUG SessionImpl:531 - opened session
 going to call identity generator to generate new id 
 identity generator generated: 
34:33,323 DEBUG SessionImpl:807 - saving [org.tolweb.hibernate.MappedAccessoryPage#&lt;null&gt;]
34:33,324 DEBUG SessionImpl:2273 - executing insertions
34:33,331 DEBUG EntityPersister:490 - Inserting entity: org.tolweb.hibernate.MappedAccessoryPage (native id)
34:33,332 DEBUG BatcherImpl:196 - about to open: 0 open PreparedStatements, 0 open ResultSets
34:33,391 DEBUG SQL:237 - 
Hibernate: null
34:33,391 DEBUG BatcherImpl:241 - preparing statement

Here's the exception:

Code:

20:34:33,391 DEBUG BatcherImpl:241 - preparing statement
java.sql.SQLException: SQL String can not be NULL
   at com.mysql.jdbc.PreparedStatement.&lt;init&gt;(PreparedStatement.java:109)
   at com.mysql.jdbc.Connection.prepareStatement(Connection.java:1358)
   at com.mysql.jdbc.Connection.prepareStatement(Connection.java:1293)
   at com.mysql.jdbc.Connection.prepareStatement(Connection.java:1393)
   at com.p6spy.engine.spy.P6Connection.prepareStatement(P6Connection.java:287)
   at org.apache.commons.dbcp.DelegatingConnection.prepareStatement(DelegatingConnection.java:370)
   at org.apache.commons.dbcp.PoolingDataSource$PoolGuardConnectionWrapper.prepareStatement(PoolingDataSource.java:415)
   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:324)
   at net.sf.hibernate.util.GetGeneratedKeysHelper.prepareStatement(GetGeneratedKeysHelper.java:39)
   at net.sf.hibernate.impl.BatcherImpl.getPreparedStatement(BatcherImpl.java:246)
   at net.sf.hibernate.impl.BatcherImpl.prepareStatement(BatcherImpl.java:61)
   at net.sf.hibernate.persister.EntityPersister.insert(EntityPersister.java:524)
   at net.sf.hibernate.persister.EntityPersister.insert(EntityPersister.java:432)
   at net.sf.hibernate.impl.ScheduledIdentityInsertion.execute(ScheduledIdentityInsertion.java:29)
   at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:906)
   at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:839)
   at net.sf.hibernate.impl.SessionImpl.saveWithGeneratedIdentifier(SessionImpl.java:757)
   at net.sf.hibernate.impl.SessionImpl.save(SessionImpl.java:720)
   at org.springframework.orm.hibernate.HibernateTemplate$8.doInHibernate(HibernateTemplate.java:242)
   at org.springframework.orm.hibernate.HibernateTemplate.execute(HibernateTemplate.java:150)
   at org.springframework.orm.hibernate.HibernateTemplate.save(HibernateTemplate.java:240)
   at org.tolweb.dao.AccessoryPageDAOImpl.addAccessoryPage(AccessoryPageDAOImpl.java:41)
   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:324)
   at org.springframework.aop.framework.AopProxyUtils.invokeJoinpointUsingReflection(AopProxyUtils.java:59)
   at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:138)
   at $Proxy3.addAccessoryPage(Unknown Source)
   at org.tolweb.dao.AccessoryPageDAOTest.testFieldsMatching(AccessoryPageDAOTest.java:165)
   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:324)
   at junit.framework.TestCase.runTest(TestCase.java:154)
   at junit.framework.TestCase.runBare(TestCase.java:127)
   at junit.framework.TestResult$1.protect(TestResult.java:106)
   at junit.framework.TestResult.runProtected(TestResult.java:124)
   at junit.framework.TestResult.run(TestResult.java:109)
   at junit.framework.TestCase.run(TestCase.java:118)
   at junit.framework.TestSuite.runTest(TestSuite.java:208)
   at junit.framework.TestSuite.run(TestSuite.java:203)
   at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.run(JUnitTestRunner.java:289)
   at org.apache.tools.ant.taskdefs.optional.junit.JUnitTask.executeInVM(JUnitTask.java:954)
   at org.apache.tools.ant.taskdefs.optional.junit.JUnitTask.execute(JUnitTask.java:626)
   at org.apache.tools.ant.taskdefs.optional.junit.JUnitTask.execute(JUnitTask.java:600)
   at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:269)
   at org.apache.tools.ant.Task.perform(Task.java:364)
   at org.apache.tools.ant.Target.execute(Target.java:301)
   at org.apache.tools.ant.Target.performTasks(Target.java:328)
   at org.apache.tools.ant.Project.executeTarget(Project.java:1215)
   at org.apache.tools.ant.Project.executeTargets(Project.java:1063)
   at org.apache.tools.ant.Main.runBuild(Main.java:632)
   at org.apache.tools.ant.Main.startAnt(Main.java:183)
   at org.apache.tools.ant.launch.Launcher.run(Launcher.java:197)
   at org.apache.tools.ant.launch.Launcher.main(Launcher.java:56)

danny_mandel · **Posted:** Thu Jul 15, 2004 12:19 pm

Hi all, I thought I would just report that I fixed the problem, though not in the original way I had planned. I ended up changing my id generator back to native and writing some raw SQL for the special case of copying between databases, like this:

Code:

Statement insertStatement = session.connection().createStatement();
insertStatement.executeUpdate("insert into ACCESSORY_PAGES (id) values (" + id + ")");
session.close();

Then, once the object is inserted into the new db, I fetch it via Hibernate and update all its values and treat it like any other Hibnernate-managed object. I hope this helps anyone who might have the same sort of whacked out ideas. :)