content/builds/1.1.0/apache-openjpa-1.1.0/docs/manual/ref_guide_meta_jpa.html - openjpa-site - Git at Google

 <html><head>
       <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
    <title>2.&nbsp; Additional JPA Metadata</title><link rel="stylesheet" href="css/docbook.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.72.0"><link rel="start" href="manual.html" title="Apache OpenJPA User's Guide"><link rel="up" href="ref_guide_meta.html" title="Chapter&nbsp;6.&nbsp; Metadata"><link rel="prev" href="ref_guide_meta.html" title="Chapter&nbsp;6.&nbsp; Metadata"><link rel="next" href="ref_guide_meta_ext.html" title="3.&nbsp; Metadata Extensions"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">2.&nbsp;
             Additional JPA Metadata
         </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ref_guide_meta.html">Prev</a>&nbsp;</td><th width="60%" align="center">Chapter&nbsp;6.&nbsp;
         Metadata
     </th><td width="20%" align="right">&nbsp;<a accesskey="n" href="ref_guide_meta_ext.html">Next</a></td></tr></table><hr></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ref_guide_meta_jpa"></a>2.&nbsp;
             Additional JPA Metadata
         </h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="ref_guide_meta_jpa.html#ref_guide_meta_jpa_datastoreid">2.1.
                 Datastore Identity
             </a></span></dt><dt><span class="section"><a href="ref_guide_meta_jpa.html#ref_guide_meta_jpa_version">2.2.
                 Surrogate Version
             </a></span></dt><dt><span class="section"><a href="ref_guide_meta_jpa.html#ref_guide_meta_jpa_persistent">2.3.
                 Persistent Field Values
             </a></span></dt><dt><span class="section"><a href="ref_guide_meta_jpa.html#ref_guide_meta_jpa_persistent_coll">2.4. Persistent Collection Fields</a></span></dt><dt><span class="section"><a href="ref_guide_meta_jpa.html#ref_guide_meta_jpa_persistent_map">2.5. Persistent Map Fields</a></span></dt></dl></div><a class="indexterm" name="d0e23053"></a><p>
 This section describes OpenJPA's core additions to standard entity metadata. We
 present the object-relational mapping syntax to support these additions in
 <a href="ref_guide_mapping_jpa.html" title="7.&nbsp; Additional JPA Mappings">Section&nbsp;7, &#8220;
             Additional JPA Mappings
         &#8221;</a>. Finally,
 <a href="ref_guide_meta_ext.html" title="3.&nbsp; Metadata Extensions">Section&nbsp;3, &#8220;
             Metadata Extensions
         &#8221;</a> covers additional extensions to JPA
 metadata that allow you to access auxiliary OpenJPA features.
         </p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_meta_jpa_datastoreid"></a>2.1.&nbsp;
                 Datastore Identity
             </h3></div></div></div><a class="indexterm" name="d0e23067"></a><p>
 JPA typically requires you to declare one or more <code class="literal">Id</code> fields
 to act as primary keys. OpenJPA, however, can create and maintain a surrogate
 primary key value when you do not declare any <code class="literal">Id</code> fields. This
 form of persistent identity is called <span class="emphasis"><em>datastore identity</em></span>.
 <a href="ref_guide_pc_oid.html" title="4.&nbsp; Object Identity">Section&nbsp;4, &#8220;
             Object Identity
         &#8221;</a> discusses OpenJPA's support for
 datastore identity in JPA. We cover how to map your datastore identity primary
 key column in <a href="ref_guide_mapping_jpa.html#ref_guide_mapping_jpa_datastoreid" title="7.1.&nbsp; Datastore Identity Mapping">Section&nbsp;7.1, &#8220;
                 Datastore Identity Mapping
             &#8221;</a>
             </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_meta_jpa_version"></a>2.2.&nbsp;
                 Surrogate Version
             </h3></div></div></div><a class="indexterm" name="d0e23090"></a><p>
 Just as OpenJPA can maintain your entity's identity without any <code class="literal">Id
 </code> fields, OpenJPA can maintain your entity's optimistic version without
 any <code class="literal">Version</code> fields.
 <a href="ref_guide_mapping_jpa.html#ref_guide_mapping_jpa_version" title="7.2.&nbsp; Surrogate Version Mapping">Section&nbsp;7.2, &#8220;
                 Surrogate Version Mapping
             &#8221;</a> shows you how to map
 surrogate version columns.
             </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_meta_jpa_persistent"></a>2.3.&nbsp;
                 Persistent Field Values
             </h3></div></div></div><a class="indexterm" name="d0e23108"></a><p>
 JPA defines <code class="literal">Basic</code>, <code class="literal">Lob</code>, <code class="literal">Embedded
 </code>, <code class="literal">ManyToOne</code>, and <code class="literal">OneToOne</code>
 persistence strategies for direct field values. OpenJPA supports all of these
 standard strategies, but adds one of its own: <code class="literal">Persistent</code>.
 The <a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/persistence/Persistent.html" target="_top">
 <code class="classname">org.apache.openjpa.persistence.Persistent</code></a>
 metadata annotation can represent any direct field value, including custom
 types. It has the following properties:
             </p><div class="itemizedlist"><ul type="disc"><li><p>
 <code class="literal">FetchType fetch</code>: Whether to load the field eagerly or
 lazily. Corresponds exactly to the same-named property of standard JPA
 annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_basic" title="2.6.&nbsp; Basic"><code class="classname"> Basic
 </code></a>. Defaults to <code class="literal">FetchType.EAGER</code>.
                     </p></li><li><p>
 <code class="literal">CascadeType[] cascade</code>: Array of enum values defining cascade
 behavior for this field. Corresponds exactly to the same-named property of
 standard JPA annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_manytoone" title="2.8.&nbsp; Many To One">
 <code class="classname"> ManyToOne</code></a>. Defaults to empty array.
                     </p></li><li><p>
 <code class="literal">String mappedBy</code>: Names the field in the related entity that
 maps this bidirectional relation. Corresponds to the same-named property of
 standard JPA annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_onetoone" title="2.10.&nbsp; One To One">
 <code class="classname"> OneToOne</code></a>.
                     </p></li><li><p>
 <code class="literal">boolean optional</code>: Whether the value can be null. Corresponds
 to the same-named property of standard JPA annotations such as
 <a href="jpa_overview_meta_field.html#jpa_overview_meta_manytoone" title="2.8.&nbsp; Many To One"><code class="classname"> ManyToOne</code>
 </a>, but can apply to non-entity object values as well. Defaults to
 <code class="literal">true</code>.
                     </p></li><li><p>
 <code class="literal">boolean embedded</code>: Set this property to <code class="literal">true
 </code> if the field value is stored as an embedded object.
                     </p></li></ul></div><p>
 Though you can use the <code class="classname">Persistent</code> annotation in place of
 most of the standard direct field annotations mentioned above, we recommend
 primarily using it for non-standard and custom types for which no standard JPA
 annotation exists. For example, <a href="ref_guide_mapping_jpa.html#ref_guide_mapping_jpa_columns" title="7.3.&nbsp; Multi-Column Mappings">Section&nbsp;7.3, &#8220;
                 Multi-Column Mappings
             &#8221;</a>
  demonstrates the use of the <code class="classname">Persistent</code> annotation
 to denote a persistent <code class="classname">java.awt.Point</code> field.
             </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_meta_jpa_persistent_coll"></a>2.4.&nbsp;Persistent Collection Fields</h3></div></div></div><a class="indexterm" name="d0e23211"></a><p>
 JPA standardizes support for collections of entities with the <code class="literal">
 OneToMany</code> and <code class="literal">ManyToMany</code> persistence strategies.
 OpenJPA supports these strategies, and may be extended for other strategies as
 well.  For extended strategies, use the
 <a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/persistence/PersistentCollection.html" target="_top">
 <code class="classname">org.apache.openjpa.persistence.PersistentCollection</code></a> metadata
 annotation to represents any persistent collection field.  It has the following
 properties:
 			</p><div class="itemizedlist"><ul type="disc"><li><p>
 <code class="literal">Class elementType</code>: The class of the collection elements.
 This information is usually taken from the parameterized collection element
 type.  You must supply it explicitly, however, if your field isn't a
 parameterized type.
 					</p></li><li><p>
 <code class="literal">FetchType fetch</code>: Whether to load the collection eagerly or
 lazily.  Corresponds exactly to the same-named property of standard JPA
 annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_basic" title="2.6.&nbsp; Basic"><code class="classname">
 Basic</code></a>. Defaults to <code class="literal">FetchType.LAZY</code>.
 					</p></li><li><p>
 <code class="literal">String mappedBy</code>: Names the field in the related entity that
 maps this bidirectional relation.  Corresponds to the same-named property of
 standard JPA annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_manytomany" title="2.11.&nbsp; Many To Many">
 <code class="classname">ManyToMany</code></a>.
 					</p></li><li><p>
 <code class="literal">CascadeType[] elementCascade</code>: Array of enum values defining
 cascade behavior for the collection elements.  Corresponds exactly to the
 <code class="literal">cascade</code> property of standard JPA annotations such as
 <a href="jpa_overview_meta_field.html#jpa_overview_meta_manytomany" title="2.11.&nbsp; Many To Many"><code class="classname">
 ManyToMany</code></a>. Defaults to empty array.
 					</p></li><li><p>
 <code class="literal">boolean elementEmbedded</code>: Set this property to <code class="literal">true
 </code> if the elements are stored as embedded objects.
 					</p></li></ul></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_meta_jpa_persistent_map"></a>2.5.&nbsp;Persistent Map Fields</h3></div></div></div><a class="indexterm" name="d0e23285"></a><p>
 JPA has limited support for maps.  If you extend JPA's standard map support to
 encompass new mappings, use the
 <a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/persistence/PersistentMap.html" target="_top">
 <code class="classname">org.apache.openjpa.persistence.PersistentMap</code></a> metadata
 annotation to represent your custom persistent map fields.  It has the
 following properties:
 			</p><div class="itemizedlist"><ul type="disc"><li><p>
 <code class="literal">Class keyType</code>: The class of the map keys.  This information
 is usually taken from the parameterized map key type.  You must supply it
 explicitly, however, if your field isn't a parameterized type.
 					</p></li><li><p>
 <code class="literal">Class elementType</code>: The class of the map values.  This
 information is usually taken from the parameterized map value type.  You must
 supply it explicitly, however, if your field isn't a parameterized type.
 					</p></li><li><p>
 <code class="literal">FetchType fetch</code>: Whether to load the collection eagerly or
 lazily.  Corresponds exactly to the same-named property of standard JPA
 annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_basic" title="2.6.&nbsp; Basic"><code class="classname">
 Basic</code></a>. Defaults to <code class="literal">FetchType.LAZY</code>.
 					</p></li><li><p>
 <code class="literal">CascadeType[] keyCascade</code>: Array of enum values defining
 cascade behavior for the map keys.  Corresponds exactly to the <code class="literal">cascade
 </code> property of standard JPA annotations such as
 <a href="jpa_overview_meta_field.html#jpa_overview_meta_manytoone" title="2.8.&nbsp; Many To One"><code class="classname">
 ManyToOne</code></a>. Defaults to empty array.
 					</p></li><li><p>
 <code class="literal">CascadeType[] elementCascade</code>: Array of enum values defining
 cascade behavior for the map values.  Corresponds exactly to the
 <code class="literal">cascade</code> property of standard JPA annotations such as
 <a href="jpa_overview_meta_field.html#jpa_overview_meta_manytoone" title="2.8.&nbsp; Many To One"><code class="classname">
 ManyToOne</code></a>. Defaults to empty array.
 					</p></li><li><p>
 <code class="literal">boolean keyEmbedded</code>: Set this property to <code class="literal">true
 </code> if the map keys are stored as embedded objects.
 					</p></li><li><p>
 <code class="literal">boolean elementEmbedded</code>: Set this property to <code class="literal">
 true</code> if the map values are stored as embedded objects.
 					</p></li></ul></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ref_guide_meta.html">Prev</a>&nbsp;</td><td width="20%" align="center"><a accesskey="u" href="ref_guide_meta.html">Up</a></td><td width="40%" align="right">&nbsp;<a accesskey="n" href="ref_guide_meta_ext.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter&nbsp;6.&nbsp;
         Metadata
     &nbsp;</td><td width="20%" align="center"><a accesskey="h" href="manual.html">Home</a></td><td width="40%" align="right" valign="top">&nbsp;3.&nbsp;
             Metadata Extensions
         </td></tr></table></div></body></html>
	<html><head>
	<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
	<title>2.  Additional JPA Metadata</title><link rel="stylesheet" href="css/docbook.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.72.0"><link rel="start" href="manual.html" title="Apache OpenJPA User's Guide"><link rel="up" href="ref_guide_meta.html" title="Chapter 6.  Metadata"><link rel="prev" href="ref_guide_meta.html" title="Chapter 6.  Metadata"><link rel="next" href="ref_guide_meta_ext.html" title="3.  Metadata Extensions"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">2.
	Additional JPA Metadata
	</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ref_guide_meta.html">Prev</a> </td><th width="60%" align="center">Chapter 6.
	Metadata
	</th><td width="20%" align="right"> <a accesskey="n" href="ref_guide_meta_ext.html">Next</a></td></tr></table><hr></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ref_guide_meta_jpa"></a>2.
	Additional JPA Metadata
	</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="ref_guide_meta_jpa.html#ref_guide_meta_jpa_datastoreid">2.1.
	Datastore Identity
	</a></span></dt><dt><span class="section"><a href="ref_guide_meta_jpa.html#ref_guide_meta_jpa_version">2.2.
	Surrogate Version
	</a></span></dt><dt><span class="section"><a href="ref_guide_meta_jpa.html#ref_guide_meta_jpa_persistent">2.3.
	Persistent Field Values
	</a></span></dt><dt><span class="section"><a href="ref_guide_meta_jpa.html#ref_guide_meta_jpa_persistent_coll">2.4. Persistent Collection Fields</a></span></dt><dt><span class="section"><a href="ref_guide_meta_jpa.html#ref_guide_meta_jpa_persistent_map">2.5. Persistent Map Fields</a></span></dt></dl></div><a class="indexterm" name="d0e23053"></a><p>
	This section describes OpenJPA's core additions to standard entity metadata. We
	present the object-relational mapping syntax to support these additions in
	<a href="ref_guide_mapping_jpa.html" title="7.  Additional JPA Mappings">Section 7, “
	Additional JPA Mappings
	”</a>. Finally,
	<a href="ref_guide_meta_ext.html" title="3.  Metadata Extensions">Section 3, “
	Metadata Extensions
	”</a> covers additional extensions to JPA
	metadata that allow you to access auxiliary OpenJPA features.
	</p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_meta_jpa_datastoreid"></a>2.1.
	Datastore Identity
	</h3></div></div></div><a class="indexterm" name="d0e23067"></a><p>
	JPA typically requires you to declare one or more <code class="literal">Id</code> fields
	to act as primary keys. OpenJPA, however, can create and maintain a surrogate
	primary key value when you do not declare any <code class="literal">Id</code> fields. This
	form of persistent identity is called <span class="emphasis"><em>datastore identity</em></span>.
	<a href="ref_guide_pc_oid.html" title="4.  Object Identity">Section 4, “
	Object Identity
	”</a> discusses OpenJPA's support for
	datastore identity in JPA. We cover how to map your datastore identity primary
	key column in <a href="ref_guide_mapping_jpa.html#ref_guide_mapping_jpa_datastoreid" title="7.1.  Datastore Identity Mapping">Section 7.1, “
	Datastore Identity Mapping
	”</a>
	</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_meta_jpa_version"></a>2.2.
	Surrogate Version
	</h3></div></div></div><a class="indexterm" name="d0e23090"></a><p>
	Just as OpenJPA can maintain your entity's identity without any <code class="literal">Id
	</code> fields, OpenJPA can maintain your entity's optimistic version without
	any <code class="literal">Version</code> fields.
	<a href="ref_guide_mapping_jpa.html#ref_guide_mapping_jpa_version" title="7.2.  Surrogate Version Mapping">Section 7.2, “
	Surrogate Version Mapping
	”</a> shows you how to map
	surrogate version columns.
	</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_meta_jpa_persistent"></a>2.3.
	Persistent Field Values
	</h3></div></div></div><a class="indexterm" name="d0e23108"></a><p>
	JPA defines <code class="literal">Basic</code>, <code class="literal">Lob</code>, <code class="literal">Embedded
	</code>, <code class="literal">ManyToOne</code>, and <code class="literal">OneToOne</code>
	persistence strategies for direct field values. OpenJPA supports all of these
	standard strategies, but adds one of its own: <code class="literal">Persistent</code>.
	The <a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/persistence/Persistent.html" target="_top">
	<code class="classname">org.apache.openjpa.persistence.Persistent</code></a>
	metadata annotation can represent any direct field value, including custom
	types. It has the following properties:
	</p><div class="itemizedlist"><ul type="disc"><li><p>
	<code class="literal">FetchType fetch</code>: Whether to load the field eagerly or
	lazily. Corresponds exactly to the same-named property of standard JPA
	annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_basic" title="2.6.  Basic"><code class="classname"> Basic
	</code></a>. Defaults to <code class="literal">FetchType.EAGER</code>.
	</p></li><li><p>
	<code class="literal">CascadeType[] cascade</code>: Array of enum values defining cascade
	behavior for this field. Corresponds exactly to the same-named property of
	standard JPA annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_manytoone" title="2.8.  Many To One">
	<code class="classname"> ManyToOne</code></a>. Defaults to empty array.
	</p></li><li><p>
	<code class="literal">String mappedBy</code>: Names the field in the related entity that
	maps this bidirectional relation. Corresponds to the same-named property of
	standard JPA annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_onetoone" title="2.10.  One To One">
	<code class="classname"> OneToOne</code></a>.
	</p></li><li><p>
	<code class="literal">boolean optional</code>: Whether the value can be null. Corresponds
	to the same-named property of standard JPA annotations such as
	<a href="jpa_overview_meta_field.html#jpa_overview_meta_manytoone" title="2.8.  Many To One"><code class="classname"> ManyToOne</code>
	</a>, but can apply to non-entity object values as well. Defaults to
	<code class="literal">true</code>.
	</p></li><li><p>
	<code class="literal">boolean embedded</code>: Set this property to <code class="literal">true
	</code> if the field value is stored as an embedded object.
	</p></li></ul></div><p>
	Though you can use the <code class="classname">Persistent</code> annotation in place of
	most of the standard direct field annotations mentioned above, we recommend
	primarily using it for non-standard and custom types for which no standard JPA
	annotation exists. For example, <a href="ref_guide_mapping_jpa.html#ref_guide_mapping_jpa_columns" title="7.3.  Multi-Column Mappings">Section 7.3, “
	Multi-Column Mappings
	”</a>
	demonstrates the use of the <code class="classname">Persistent</code> annotation
	to denote a persistent <code class="classname">java.awt.Point</code> field.
	</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_meta_jpa_persistent_coll"></a>2.4. Persistent Collection Fields</h3></div></div></div><a class="indexterm" name="d0e23211"></a><p>
	JPA standardizes support for collections of entities with the <code class="literal">
	OneToMany</code> and <code class="literal">ManyToMany</code> persistence strategies.
	OpenJPA supports these strategies, and may be extended for other strategies as
	well. For extended strategies, use the
	<a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/persistence/PersistentCollection.html" target="_top">
	<code class="classname">org.apache.openjpa.persistence.PersistentCollection</code></a> metadata
	annotation to represents any persistent collection field. It has the following
	properties:
	</p><div class="itemizedlist"><ul type="disc"><li><p>
	<code class="literal">Class elementType</code>: The class of the collection elements.
	This information is usually taken from the parameterized collection element
	type. You must supply it explicitly, however, if your field isn't a
	parameterized type.
	</p></li><li><p>
	<code class="literal">FetchType fetch</code>: Whether to load the collection eagerly or
	lazily. Corresponds exactly to the same-named property of standard JPA
	annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_basic" title="2.6.  Basic"><code class="classname">
	Basic</code></a>. Defaults to <code class="literal">FetchType.LAZY</code>.
	</p></li><li><p>
	<code class="literal">String mappedBy</code>: Names the field in the related entity that
	maps this bidirectional relation. Corresponds to the same-named property of
	standard JPA annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_manytomany" title="2.11.  Many To Many">
	<code class="classname">ManyToMany</code></a>.
	</p></li><li><p>
	<code class="literal">CascadeType[] elementCascade</code>: Array of enum values defining
	cascade behavior for the collection elements. Corresponds exactly to the
	<code class="literal">cascade</code> property of standard JPA annotations such as
	<a href="jpa_overview_meta_field.html#jpa_overview_meta_manytomany" title="2.11.  Many To Many"><code class="classname">
	ManyToMany</code></a>. Defaults to empty array.
	</p></li><li><p>
	<code class="literal">boolean elementEmbedded</code>: Set this property to <code class="literal">true
	</code> if the elements are stored as embedded objects.
	</p></li></ul></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_meta_jpa_persistent_map"></a>2.5. Persistent Map Fields</h3></div></div></div><a class="indexterm" name="d0e23285"></a><p>
	JPA has limited support for maps. If you extend JPA's standard map support to
	encompass new mappings, use the
	<a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/persistence/PersistentMap.html" target="_top">
	<code class="classname">org.apache.openjpa.persistence.PersistentMap</code></a> metadata
	annotation to represent your custom persistent map fields. It has the
	following properties:
	</p><div class="itemizedlist"><ul type="disc"><li><p>
	<code class="literal">Class keyType</code>: The class of the map keys. This information
	is usually taken from the parameterized map key type. You must supply it
	explicitly, however, if your field isn't a parameterized type.
	</p></li><li><p>
	<code class="literal">Class elementType</code>: The class of the map values. This
	information is usually taken from the parameterized map value type. You must
	supply it explicitly, however, if your field isn't a parameterized type.
	</p></li><li><p>
	<code class="literal">FetchType fetch</code>: Whether to load the collection eagerly or
	lazily. Corresponds exactly to the same-named property of standard JPA
	annotations such as <a href="jpa_overview_meta_field.html#jpa_overview_meta_basic" title="2.6.  Basic"><code class="classname">
	Basic</code></a>. Defaults to <code class="literal">FetchType.LAZY</code>.
	</p></li><li><p>
	<code class="literal">CascadeType[] keyCascade</code>: Array of enum values defining
	cascade behavior for the map keys. Corresponds exactly to the <code class="literal">cascade
	</code> property of standard JPA annotations such as
	<a href="jpa_overview_meta_field.html#jpa_overview_meta_manytoone" title="2.8.  Many To One"><code class="classname">
	ManyToOne</code></a>. Defaults to empty array.
	</p></li><li><p>
	<code class="literal">CascadeType[] elementCascade</code>: Array of enum values defining
	cascade behavior for the map values. Corresponds exactly to the
	<code class="literal">cascade</code> property of standard JPA annotations such as
	<a href="jpa_overview_meta_field.html#jpa_overview_meta_manytoone" title="2.8.  Many To One"><code class="classname">
	ManyToOne</code></a>. Defaults to empty array.
	</p></li><li><p>
	<code class="literal">boolean keyEmbedded</code>: Set this property to <code class="literal">true
	</code> if the map keys are stored as embedded objects.
	</p></li><li><p>
	<code class="literal">boolean elementEmbedded</code>: Set this property to <code class="literal">
	true</code> if the map values are stored as embedded objects.
	</p></li></ul></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ref_guide_meta.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ref_guide_meta.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ref_guide_meta_ext.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 6.
	Metadata
	</td><td width="20%" align="center"><a accesskey="h" href="manual.html">Home</a></td><td width="40%" align="right" valign="top"> 3.
	Metadata Extensions
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