Hibernate example source code file (tutorial_envers.xml)

This example Hibernate source code file (tutorial_envers.xml) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

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The Hibernate tutorial_envers.xml source code

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">

<chapter id="hibernate-gsg-tutorial-envers">
    <title>Tutorial Using Envers

    <para>
      This tutorial is located within the download bundle under <filename>envers.
    </para>
    <itemizedlist>
      <title>Objectives
      <listitem>
        <para>
          Configure Envers.
        </para>
      </listitem>
      <listitem>
        <para>
          Use the Envers APIs to view and analyze historical data.
        </para>
      </listitem>
    </itemizedlist>

    <section id="hibernate-gsg-tutorial-envers-config">
      <title>persistence.xml
      <para>
        This file was discussed in the <systemitem>JPA tutorial in 
      <para>
        Again, the entity is largely the same as in <xref linkend="hibernate-gsg-tutorial-jpa-entity" />.  The major
        difference is the addition of the <interfacename>@org.hibernate.envers.Audited annotation, which
        tells Envers to automatically track changes to this entity.
      </para>
    </section>

    <section id="hibernate-gsg-tutorial-envers-test">
      <title>Example code
      <para>
        Again, this tutorial makes use of the <systemitem>JPA APIs.  However, the code also makes a change to one
        of the entities, then uses the Envers API to pull back the initial <firstterm>revision as well as the updated
        revision. A revision refers to a version of an entity.
      </para>
      <example id="hibernate-gsg-tutorial-envers-test-api">
        <title>Using the org.hibernate.envers.AuditReader
        <programlisting role="JAVA">public void testBasicUsage() {
    ...
    AuditReader reader = AuditReaderFactory.get( entityManager );
    Event firstRevision = reader.find( Event.class, 2L, 1 );
    ...
    Event secondRevision = reader.find( Event.class, 2L, 2 );
    ...
}</programlisting>
      </example>
      <procedure>
        <title>Description of Example
        <step>
          <para>
            An <interfacename>org.hibernate.envers.AuditReader is obtained from the
            <classname>org.hibernate.envers.AuditReaderFactory which wraps the
            <interfacename>javax.persistence.EntityManager.
          </para>
        </step>
        <step>
          <para>
            Next, the <methodname>find method retrieves specific revisions of the entity.  The first call
            reads <literal>find revision number 1 of Event with id 2.  The second call reads find
            revision number 2 of Event with id 2</literal>.
          </para>
        </step>
      </procedure>
    </section>

    <section id="hibernate-gsg-tutorial-annotations-further">
      <title>Take it further!
      <itemizedlist>
        <title>Practice Exercises
        <listitem>
            <para>
                Provide a custom revision entity to additionally capture who made the changes.
            </para>
        </listitem>
        <listitem>
            <para>
                Write a query to retrieve only historical data which meets some criteria. Use the
                <citetitle pubwork="book">Envers User Guide to see how Envers queries are constructed.
            </para>
        </listitem>
        <listitem>
            <para>
                Experiment with auditing entities which have many-to-one, many-to-many relations as well as collections.
                Try retrieving historical versions (revisions) of such entities and navigating the object tree.
            </para>
        </listitem>
      </itemizedlist>
    </section>

</chapter>