Persisting An Annotation-Less POJO With JPA

To persist an annotation-less POJO with JPA:


public class Workshop {

    private long id;
    private String name;

    public Workshop() {
    }

    public Workshop(long id, String name) {
        this.id = id;
        this.name = name;
    }
}


you will have to provide the lacking metadata in a XML descriptor instead of annotations:

<?xml version="1.0" encoding="UTF-8" ?>
<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
                 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                 xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm orm_2_0.xsd"
                 version="2.0">
    <entity class="com.airhacks.jpa.orm.Workshop">
        <table name="T_WORKSHOP"/>
        <attributes>
            <id name="id">
                <generated-value strategy="AUTO"/>
            </id>
            <basic name="name">
                <column name="w_name" length="100"/>
            </basic>
        </attributes>
    </entity>
</entity-mappings>

The persistence.xml file has to point to the location of the orm.xml:


<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
                http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
    <persistence-unit name="it" transaction-type="RESOURCE_LOCAL">

        <mapping-file>META-INF/orm.xml</mapping-file>

        <exclude-unlisted-classes>true</exclude-unlisted-classes>
        <properties>
            <property name="javax.persistence.jdbc.url"
                      value="jdbc:derby:./airhacksDB;create=true"/>
            <property name="javax.persistence.jdbc.driver"
                      value="org.apache.derby.jdbc.EmbeddedDriver"/>
            <property name="javax.persistence.schema-generation.database.action"
                      value="drop-and-create"/>
        </properties>
    </persistence-unit>
</persistence>

Now an annotation-less POJO can be stored using JPA:


import com.airhacks.rulz.em.EntityManagerProvider;
import org.junit.Rule;
import org.junit.Test;

public class WorkshopIT {

    @Rule
    public EntityManagerProvider provider = EntityManagerProvider.persistenceUnit("it");

    @Test
    public void crud() {
        provider.tx().begin();
        provider.em().merge(new Workshop());
        provider.tx().commit();
    }

}

The idea for this post came from 16th airhacks.tv Q&A. Big thanks to Eddy Young for asking this question.

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Comments:

Why? For god sake, why? Ten years ago maybe, but now?

Posted by Jirka Pinkas on July 10, 2015 at 08:55 AM CEST #

Reminds me of Hibernate hbm mapping files. Never again!

Posted by javaservant on July 10, 2015 at 11:06 PM CEST #

Just want to know whether the input
<mapping-file>META-INF/orm.xml</mapping-file> is obligaroty in the persistence.xml-File? I was thinking that, it will be always picks up, when it's present.

Posted by Gilles on July 20, 2015 at 03:57 PM CEST #

For those asking "why": because you don't always control the POJO implementation?

Posted by Thom on August 26, 2015 at 04:51 PM CEST #

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