mirror of https://github.com/apache/openjpa.git
OPENJPA-1932: Documentation update: Extract entity locking to a new section and add missing lock modes defined in JPA 2.0.
git-svn-id: https://svn.apache.org/repos/asf/openjpa/trunk@1095186 13f79535-47bb-0310-9956-ffa450edef68
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Milosz Tylenda
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c2b3e11a78
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@ -494,53 +494,6 @@ whose <link linkend="jpa_overview_meta_cascade">cascades</link> include
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</para>
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</listitem>
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</itemizedlist>
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<programlisting>
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public void lock(Object entity, LockModeType mode);
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</programlisting>
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<para>
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<indexterm>
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<primary>
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EntityManager
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</primary>
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<secondary>
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lock
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</secondary>
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</indexterm>
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<indexterm>
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<primary>
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locking
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</primary>
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<seealso>
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EntityManager
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</seealso>
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</indexterm>
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This method locks the given entity using the named mode. The
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<ulink url="http://download.oracle.com/javaee/6/api/javax/persistence/LockModeType.html">
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<classname>javax.persistence.LockModeType</classname></ulink> enum defines two
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modes:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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<literal>READ</literal>: Other transactions may concurrently read the object,
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but cannot concurrently update it.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>WRITE</literal>: Other transactions cannot concurrently read or write
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the object. When a transaction is committed that holds WRITE locks on any
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entities, those entities will have their version incremented even if the entities
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themselves did not change in the transaction.
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</para>
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</listitem>
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</itemizedlist>
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<note>
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<para>
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OpenJPA has additional APIs for controlling object locking. See
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<xref linkend="ref_guide_locking"/> in the Reference Guide for details.
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</para>
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</note>
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<para>
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The following diagram illustrates the lifecycle of an entity with respect to the
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APIs presented in this section.
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@ -1025,6 +978,113 @@ language. For relational databases, this is the Structured Query Language (SQL).
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native query support.
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</para>
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</section>
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<section id="jpa_overview_em_locking">
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<title>
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Entity Locking
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</title>
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<indexterm zone="jpa_overview_em_locking">
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<primary>
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EntityManager
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</primary>
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<secondary>
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locking
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</secondary>
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</indexterm>
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<programlisting>
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public void lock(Object entity, LockModeType mode);
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</programlisting>
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<para>
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<indexterm>
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<primary>
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EntityManager
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</primary>
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<secondary>
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lock
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</secondary>
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</indexterm>
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<indexterm>
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<primary>
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locking
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</primary>
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<seealso>
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EntityManager
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</seealso>
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</indexterm>
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This method locks the given entity using the named mode. The
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<ulink url="http://download.oracle.com/javaee/6/api/javax/persistence/LockModeType.html">
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<classname>javax.persistence.LockModeType</classname></ulink> enum defines eight
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modes:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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<literal>OPTIMISTIC</literal>: Optimistic locking.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>OPTIMISTIC_FORCE_INCREMENT</literal>: Optimistic locking.
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When a transaction is committed, the entity's version column
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will be incremented even if the entity's state did not change in the transaction.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>PESSIMISTIC_READ</literal>: Pessimistic locking. Other transactions
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may concurrently read the entity, but cannot concurrently update it.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>PESSIMISTIC_WRITE</literal>: Pessimistic locking. Other transactions
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cannot concurrently read or write the entity.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>PESSIMISTIC_FORCE_INCREMENT</literal>: Pessimistic locking. Other transactions
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cannot concurrently read or write the entity.
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When a transaction is committed, the entity's version column
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will be incremented even if the entity's state did not change in the transaction.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>READ</literal>: A synonym for <literal>OPTIMISTIC</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>WRITE</literal>: A synonym for <literal>OPTIMISTIC_FORCE_INCREMENT</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>NONE</literal>: No locking is performed.
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</para>
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</listitem>
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</itemizedlist>
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<note>
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<itemizedlist>
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<listitem>
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<para>
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OpenJPA differentiates between <literal>PESSIMISTIC_READ</literal> and
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<literal>PESSIMISTIC_WRITE</literal> lock modes only with DB2 databases.
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While running with other databases, there is no distinction between these
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two modes because
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<literal>PESSIMISTIC_READ</literal> lock mode
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is upgraded to <literal>PESSIMISTIC_WRITE</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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OpenJPA has additional APIs for controlling entity locking. See
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<xref linkend="ref_guide_locking"/> in the Reference Guide for details.
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</para>
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</listitem>
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</itemizedlist>
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</note>
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</section>
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<section id="jpa_overview_em_properties">
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<title>
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Retrieving Properties Information
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