mojavelinux/apache-tomee-datanucleus.adoc

## apache-tomee-datanucleus.adoc

      
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              apache-tomee-datanucleus.adoc
            
          
    Using DataNucleus as the JPA provider in Apache TomEE


DataNucleus can be used as an alternate JPA provider in TomEE.
This document describes how to make this switch.
These instructions assume you are using container-managed JPA.
For context, see the project at https://github.com/mojavelinux/apache-tomee-datanucleus-test.


For the Arquillian TomEE Embedded adapter and the DataNucleus entity enhancer, add the following provided-scope dependencies to the main <dependencies> element:


<dependency>
    <groupId>org.datanucleus</groupId>
    <artifactId>datanucleus-core</artifactId>
    <version>5.0.7</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>org.datanucleus</groupId>
    <artifactId>datanucleus-api-jpa</artifactId>
    <version>5.0.8</version>
    <scope>provided</scope>
</dependency>


Also add the following test-scoped dependency to the arquillian=tomee-embedded profile:


<dependency>
    <groupId>org.datanucleus</groupId>
    <artifactId>datanucleus-rdbms</artifactId>
    <version>5.0.7</version>
    <scope>test</scope>
</dependency>


DataNucleus needs to enhance the entity classes.
This step can be done at compile time using a Maven plugin.
To configure the DataNucleus Maven plugin to enhance the entity classes, add the following plugin declaration to the plugins under the main <build> element:


<plugin>
    <groupId>org.datanucleus</groupId>
    <artifactId>datanucleus-maven-plugin</artifactId>
    <version>5.0.2</version>
    <configuration>
        <api>JPA</api>
        <persistenceUnitName>SecretAgentPU</persistenceUnitName>
    </configuration>
    <executions>
        <execution>
            <phase>process-classes</phase>
            <goals>
                <goal>enhance</goal>
            </goals>
        </execution>
    </executions>
</plugin>


❗


Update the name of the persistence unit in this configuration to match the value of the persistence unit defined in persistence.xml.


📎


The alternative approach is runtime enhancement, which is performed using a javaagent.


To add DataNucleus to the standalone TomEE instance, which is used by the TomEE managed adapter, add the following entries to the <libs> element inside the <configuration> element of the tomee-maven-plugin:


<lib>org.datanucleus:datanucleus-core:5.0.7</lib>
<lib>org.datanucleus:datanucleus-api-jpa:5.0.8</lib>
<lib>org.datanucleus:datanucleus-rdbms:5.0.7</lib>


Run the tomee:build goal to rebuild the TomEE instance:


$ mvn tomee:build -Dtomee-plugin.skipCurrentProject=true


Now that the requisite dependencies and enhancer plugin have been added, configure DataNucleus as the JPA provider in the persistence descriptor (i.e., persistence.xml):


<provider>org.datanucleus.api.jpa.PersistenceProviderImpl</provider>


Also add the following property to the persistence descriptor:


<!-- prevent DataNucleus from messing with the case we use in the mappings -->
<property name="datanucleus.identifier.case" value="MixedCase"/>


⚠️


When using DataNucleus, PersistenceUtilUtil#isLoaded(Object, String) forces a lazy association to load instead of checking whether it’s already loaded.


To enable SQL logging, you need to add the following setting to your logging.properties file:


DataNucleus.Datastore.level = FINE


And away you go!