content/builds/2.4.2/apache-openjpa/docs/ref_guide_mapping_defaults.html - openjpa-site - Git at Google

 <html><head>
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    <title>4.&nbsp; Mapping Defaults</title><base href="display"><link rel="stylesheet" type="text/css" href="css/docbook.css"><meta name="generator" content="DocBook XSL Stylesheets V1.79.1"><link rel="home" href="manual.html" title="Apache OpenJPA 2.4 User's Guide"><link rel="up" href="ref_guide_mapping.html" title="Chapter&nbsp;7.&nbsp; Mapping"><link rel="prev" href="ref_guide_mapping_middle.html" title="3.&nbsp; Meet-in-the-Middle Mapping"><link rel="next" href="ref_guide_mapping_factory.html" title="5.&nbsp; Mapping Factory"></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">4.&nbsp;
             Mapping Defaults
         </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ref_guide_mapping_middle.html">Prev</a>&nbsp;</td><th width="60%" align="center">Chapter&nbsp;7.&nbsp;
         Mapping
     </th><td width="20%" align="right">&nbsp;<a accesskey="n" href="ref_guide_mapping_factory.html">Next</a></td></tr></table><hr></div><div class="section" id="ref_guide_mapping_defaults"><div class="titlepage"><div><div><h2 class="title" style="clear: both">4.&nbsp;
             Mapping Defaults
         </h2></div></div></div>

         <a class="indexterm" name="d5e14021"></a>
         <a class="indexterm" name="d5e14023"></a>
         <p>
 The previous sections showed how to use the mapping tool to generate default
 mappings. But how does the mapping tool know what mappings to generate? The
 answer lies in the
 <a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/MappingDefaults.html" target="_top">
 <code class="classname">org.apache.openjpa.jdbc.meta.MappingDefaults</code></a>
 interface. OpenJPA uses an instance of this interface to decide how to name
 tables and columns, where to put foreign keys, and generally how to create a
 schema that matches your object model.
         </p>
         <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Important</h3>
             <p>
 OpenJPA relies on foreign key constraint information at runtime to order SQL
 appropriately. Be sure to set your mapping defaults to reflect your existing
 database constraints, set the schema factory to reflect on the database for
 constraint information (see <a class="xref" href="ref_guide_schema_info.html#ref_guide_schema_info_factory" title="12.2.&nbsp; Schema Factory">Section&nbsp;12.2, &#8220;
                 Schema Factory
             &#8221;</a>),
 or use explicit foreign key mappings as described in
 <a class="xref" href="ref_guide_mapping_jpa.html#ref_guide_mapping_jpa_fk" title="7.9.2.&nbsp; Foreign Keys">Section&nbsp;7.9.2, &#8220;
                     Foreign Keys
                 &#8221;</a>.
             </p>
         </div>
         <p>
 The <a class="link" href="ref_guide_conf_jdbc.html#openjpa.jdbc.MappingDefaults" title="6.8.&nbsp; openjpa.jdbc.MappingDefaults"><code class="literal">
 openjpa.jdbc.MappingDefaults</code></a> configuration property controls
 the <code class="classname">MappingDefaults</code> interface implementation in use. This
 is a plugin property (see <a class="xref" href="ref_guide_conf_plugins.html" title="4.&nbsp; Plugin Configuration">Section&nbsp;4, &#8220;
             Plugin Configuration
         &#8221;</a>), so
 you can substitute your own implementation or configure the existing ones.
 OpenJPA includes the following standard implementations:
         </p>
         <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
                 <p>
 <code class="literal">jpa</code>: Provides defaults in compliance with the JPA standard.
 This is an alias for the
 <a class="ulink" href="../javadoc/org/apache/openjpa/persistence/jdbc/PersistenceMappingDefaults.html" target="_top">
 <code class="classname">org.apache.openjpa.persistence.jdbc.PersistenceMappingDefaults
 </code></a> class. This class extends the <code class="classname">
 MappingDefaultsImpl</code> class described below, so it has all the same
 properties (though with different default values), as well as:
                 </p>
                 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem">
                         <p>
 <code class="literal">PrependFieldNameToJoinTableInverseJoinColumns</code>: Whether to
 prepend the owning field name to the names of inverse join columns in join
 tables.  Defaults to true per the JPA specification.  Set to false for
 compatibility with older OpenJPA versions which did not prepend the field name.
                         </p>
                     </li></ul></div>
             </li><li class="listitem">
                 <p>
 <code class="literal">default</code>: This is an alias for the
 <a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/MappingDefaultsImpl.html" target="_top">
 <code class="classname">org.apache.openjpa.jdbc.meta.MappingDefaultsImpl</code></a>
 class. This default implementation is highly configurable. It has the following
 properties:
                 </p>
                 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem">
                         <p>
 <code class="literal">DefaultMissingInfo</code>: Whether to default missing column and
 table names rather than throw an exception. If set to false, full explicit
 mappings are required at runtime and when using mapping tool actions like
 <code class="literal">buildSchema</code> and <code class="literal">validate</code>.
                         </p>
                     </li><li class="listitem">
                         <p>
 <a class="indexterm" name="d5e14063"></a>
 <code class="literal">RemoveHungarianNotation</code>: Switches on/off removal of
 Hungarian notation when generating column names.
 Fields such as <code class="literal">mFoobar</code> and <code class="literal">strBarFoo</code>
 would become columns named <code class="literal">foobar</code> and
 <code class="literal">barfoo</code> respectively. OpenJPA will search for the first
 instance of a uppercase character in the field name and then truncate the
 column name to remove anything before it.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">BaseClassStrategy</code>: The default mapping strategy for base
 classes. You can specify a built-in strategy alias or the full class name of a
 <a class="link" href="ref_guide_mapping_custom.html#ref_guide_mapping_custom_class" title="10.1.&nbsp; Custom Class Mapping">custom class strategy</a>.
 You can also use OpenJPA's plugin format (see
 <a class="xref" href="ref_guide_conf_plugins.html" title="4.&nbsp; Plugin Configuration">Section&nbsp;4, &#8220;
             Plugin Configuration
         &#8221;</a>) to pass arguments to the
 strategy instance. See the
 <a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/strats/package-summary.html" target="_top">
 <code class="literal">org.apache.openjpa.jdbc.meta.strats</code></a> package for
 available strategies.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">SubclassStrategy</code>: The default mapping strategy for
 subclasses. You can specify a builtin strategy alias or the full class name of a
 <a class="link" href="ref_guide_mapping_custom.html#ref_guide_mapping_custom_class" title="10.1.&nbsp; Custom Class Mapping"> custom class strategy</a>.
 You can also use OpenJPA's plugin format (see
 <a class="xref" href="ref_guide_conf_plugins.html" title="4.&nbsp; Plugin Configuration">Section&nbsp;4, &#8220;
             Plugin Configuration
         &#8221;</a>) to pass arguments to the
 strategy instance. Common strategies are <code class="literal">vertical</code> and
 <code class="literal">flat</code>, the default. See the
 <a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/strats/package-summary.html" target="_top">
 <code class="literal">org.apache.openjpa.jdbc.meta.strats</code></a> package for all
 available strategies.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">VersionStrategy</code>: The default version strategy for classes
 without a version field. You can specify a builtin strategy alias or the full
 class name of a <a class="link" href="ref_guide_mapping_custom.html#ref_guide_mapping_custom_versdiscrim" title="10.2.&nbsp; Custom Discriminator and Version Strategies"> custom
 version strategy</a>. You can also use OpenJPA's plugin format (see
 <a class="xref" href="ref_guide_conf_plugins.html" title="4.&nbsp; Plugin Configuration">Section&nbsp;4, &#8220;
             Plugin Configuration
         &#8221;</a>) to pass arguments to the
 strategy instance. Common strategies are <code class="literal">none</code>, <code class="literal">
 state-comparison</code>, <code class="literal"> timestamp</code>, and <code class="literal">
 version-number</code>, the default. See the
 <a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/strats/package-summary.html" target="_top">
 <code class="literal">org.apache.openjpa.jdbc.meta.strats</code></a> package for all
 available strategies.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">DiscriminatorStrategy</code>: The default discriminator strategy
 when no discriminator value is given. You can specify a builtin strategy alias
 or the full class name of a
 <a class="link" href="ref_guide_mapping_custom.html#ref_guide_mapping_custom_versdiscrim" title="10.2.&nbsp; Custom Discriminator and Version Strategies"> custom discriminator
 strategy</a>. You can also use OpenJPA's plugin format (see
 <a class="xref" href="ref_guide_conf_plugins.html" title="4.&nbsp; Plugin Configuration">Section&nbsp;4, &#8220;
             Plugin Configuration
         &#8221;</a>) to pass arguments to the
 strategy instance. Common strategies are <code class="literal">final</code> for a base
 class without subclasses, <code class="literal">none</code> to use joins to subclass
 tables rather than a discriminator column, and <code class="literal"> class-name</code>,
 the default. See the
 <a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/strats/package-summary.html" target="_top">
 <code class="literal">org.apache.openjpa.jdbc.meta.strats</code></a> package for all
 available strategies.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">FieldStrategies</code>: This property associates field types with
 custom strategies. The format of this property is similar to that of plugin
 strings (see <a class="xref" href="ref_guide_conf_plugins.html" title="4.&nbsp; Plugin Configuration">Section&nbsp;4, &#8220;
             Plugin Configuration
         &#8221;</a> ), without the class
 name. It is a comma-separated list of key/value pairs, where each key is a
 possible field type, and each value is itself a plugin string describing the
 strategy for that type. We present an example below. See
 <a class="xref" href="ref_guide_mapping_custom.html#ref_guide_mapping_custom_field" title="10.3.&nbsp; Custom Field Mapping">Section&nbsp;10.3, &#8220;
                 Custom Field Mapping
             &#8221;</a> for information on custom
 field strategies.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">ForeignKeyDeleteAction</code>: The default delete action of foreign
 keys representing relations to other objects. Recognized values include
 <code class="literal">restrict</code>, <code class="literal">cascade</code>, <code class="literal">null</code>
 , <code class="literal">default</code>. These values correspond exactly to the standard
 database foreign key actions of the same names.
                         </p>
                         <p>
 The value <code class="literal">none</code> tells OpenJPA not to create database foreign
 keys on relation columns. This is the default.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">JoinForeignKeyDeleteAction</code>: The default delete action of
 foreign keys that join secondary, collection, map, or subclass tables to
 the primary table. Accepts the same values as the <code class="literal">
 ForeignKeyDeleteAction</code> property above.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">DeferConstraints</code>: Whether to use deferred database
 constraints if possible. Defaults to false.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">IndexLogicalForeignKeys</code>: Boolean property controlling
 whether to create indexes on logical foreign keys. Logical foreign keys are
 columns that represent a link between tables, but have been configured through
 the <code class="literal">ForeignKey</code> properties above not to use a physical
 database foreign key. Defaults to true.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">DataStoreIdColumnName</code>: The default name of datastore
 identity columns.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">DiscriminatorColumnName</code>: The default name of discriminator
 columns.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">IndexDiscriminator</code>: Whether to index the discriminator
 column. Defaults to true.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">VersionColumnName</code>: The default name of version columns.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">IndexVersion</code>: Whether to index the version column. Defaults
 to false.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">AddNullIndicator</code>: Whether to create a synthetic null
 indicator column for embedded mappings. The null indicator column allows OpenJPA
 to distinguish between a null embedded object and one with default values for
 all persistent fields.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">NullIndicatorColumnName</code>: The default name of synthetic null
 indicator columns for embedded objects.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">OrderLists</code>: Whether to create a database ordering column for
 maintaining the order of persistent lists and arrays.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">OrderColumnName</code>: The default name of collection and array
 ordering columns.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">StoreEnumOrdinal</code>: Set to true to store enum fields as
 numeric ordinal values in the database. The default is to store the enum value
 name as a string, which is more robust if the Java enum declaration might be
 rearranged.
                         </p>
                     </li><li class="listitem">
                         <p>
 <code class="literal">StoreUnmappedObjectIdString</code>: Set to true to store the
 stringified identity of related objects when the declared related type is
 unmapped. By default, OpenJPA stores the related object's primary key value(s).
 However, this breaks down if different subclasses of the related type use
 incompatible primary key structures. In that case, stringifying the identity
 value is the better choice.
                         </p>
                     </li></ul></div>
             </li></ul></div>
         <p>
 The example below turns on foreign key generation during schema creation and
 associates the <code class="classname">org.mag.data.InfoStruct</code> field type with
 the custom <code class="classname">org.mag.mapping.InfoStructHandler</code> value
 handler.
         </p>
         <div class="example" id="ref_guide_mapping_defaults_conf"><p class="title"><b>Example&nbsp;7.12.&nbsp;
                 Configuring Mapping Defaults
             </b></p><div class="example-contents">

 <pre class="programlisting">
 &lt;property name="openjpa.jdbc.MappingDefaults"
     value="ForeignKeyDeleteAction=restrict,
     FieldStrategies='org.mag.data.InfoStruct=org.mag.mapping.InfoStructHandler'"/&gt;
 </pre>
         </div></div><br class="example-break">
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             Meet-in-the-Middle Mapping
         &nbsp;</td><td width="20%" align="center"><a accesskey="h" href="manual.html">Home</a></td><td width="40%" align="right" valign="top">&nbsp;5.&nbsp;
             Mapping Factory
         </td></tr></table></div></body></html>
	<html><head>
	<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
	<title>4.  Mapping Defaults</title><base href="display"><link rel="stylesheet" type="text/css" href="css/docbook.css"><meta name="generator" content="DocBook XSL Stylesheets V1.79.1"><link rel="home" href="manual.html" title="Apache OpenJPA 2.4 User's Guide"><link rel="up" href="ref_guide_mapping.html" title="Chapter 7.  Mapping"><link rel="prev" href="ref_guide_mapping_middle.html" title="3.  Meet-in-the-Middle Mapping"><link rel="next" href="ref_guide_mapping_factory.html" title="5.  Mapping Factory"></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">4.
	Mapping Defaults
	</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ref_guide_mapping_middle.html">Prev</a> </td><th width="60%" align="center">Chapter 7.
	Mapping
	</th><td width="20%" align="right"> <a accesskey="n" href="ref_guide_mapping_factory.html">Next</a></td></tr></table><hr></div><div class="section" id="ref_guide_mapping_defaults"><div class="titlepage"><div><div><h2 class="title" style="clear: both">4.
	Mapping Defaults
	</h2></div></div></div>

	<a class="indexterm" name="d5e14021"></a>
	<a class="indexterm" name="d5e14023"></a>
	<p>
	The previous sections showed how to use the mapping tool to generate default
	mappings. But how does the mapping tool know what mappings to generate? The
	answer lies in the
	<a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/MappingDefaults.html" target="_top">
	<code class="classname">org.apache.openjpa.jdbc.meta.MappingDefaults</code></a>
	interface. OpenJPA uses an instance of this interface to decide how to name
	tables and columns, where to put foreign keys, and generally how to create a
	schema that matches your object model.
	</p>
	<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Important</h3>
	<p>
	OpenJPA relies on foreign key constraint information at runtime to order SQL
	appropriately. Be sure to set your mapping defaults to reflect your existing
	database constraints, set the schema factory to reflect on the database for
	constraint information (see <a class="xref" href="ref_guide_schema_info.html#ref_guide_schema_info_factory" title="12.2.  Schema Factory">Section 12.2, “
	Schema Factory
	”</a>),
	or use explicit foreign key mappings as described in
	<a class="xref" href="ref_guide_mapping_jpa.html#ref_guide_mapping_jpa_fk" title="7.9.2.  Foreign Keys">Section 7.9.2, “
	Foreign Keys
	”</a>.
	</p>
	</div>
	<p>
	The <a class="link" href="ref_guide_conf_jdbc.html#openjpa.jdbc.MappingDefaults" title="6.8.  openjpa.jdbc.MappingDefaults"><code class="literal">
	openjpa.jdbc.MappingDefaults</code></a> configuration property controls
	the <code class="classname">MappingDefaults</code> interface implementation in use. This
	is a plugin property (see <a class="xref" href="ref_guide_conf_plugins.html" title="4.  Plugin Configuration">Section 4, “
	Plugin Configuration
	”</a>), so
	you can substitute your own implementation or configure the existing ones.
	OpenJPA includes the following standard implementations:
	</p>
	<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
	<p>
	<code class="literal">jpa</code>: Provides defaults in compliance with the JPA standard.
	This is an alias for the
	<a class="ulink" href="../javadoc/org/apache/openjpa/persistence/jdbc/PersistenceMappingDefaults.html" target="_top">
	<code class="classname">org.apache.openjpa.persistence.jdbc.PersistenceMappingDefaults
	</code></a> class. This class extends the <code class="classname">
	MappingDefaultsImpl</code> class described below, so it has all the same
	properties (though with different default values), as well as:
	</p>
	<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem">
	<p>
	<code class="literal">PrependFieldNameToJoinTableInverseJoinColumns</code>: Whether to
	prepend the owning field name to the names of inverse join columns in join
	tables. Defaults to true per the JPA specification. Set to false for
	compatibility with older OpenJPA versions which did not prepend the field name.
	</p>
	</li></ul></div>
	</li><li class="listitem">
	<p>
	<code class="literal">default</code>: This is an alias for the
	<a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/MappingDefaultsImpl.html" target="_top">
	<code class="classname">org.apache.openjpa.jdbc.meta.MappingDefaultsImpl</code></a>
	class. This default implementation is highly configurable. It has the following
	properties:
	</p>
	<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem">
	<p>
	<code class="literal">DefaultMissingInfo</code>: Whether to default missing column and
	table names rather than throw an exception. If set to false, full explicit
	mappings are required at runtime and when using mapping tool actions like
	<code class="literal">buildSchema</code> and <code class="literal">validate</code>.
	</p>
	</li><li class="listitem">
	<p>
	<a class="indexterm" name="d5e14063"></a>
	<code class="literal">RemoveHungarianNotation</code>: Switches on/off removal of
	Hungarian notation when generating column names.
	Fields such as <code class="literal">mFoobar</code> and <code class="literal">strBarFoo</code>
	would become columns named <code class="literal">foobar</code> and
	<code class="literal">barfoo</code> respectively. OpenJPA will search for the first
	instance of a uppercase character in the field name and then truncate the
	column name to remove anything before it.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">BaseClassStrategy</code>: The default mapping strategy for base
	classes. You can specify a built-in strategy alias or the full class name of a
	<a class="link" href="ref_guide_mapping_custom.html#ref_guide_mapping_custom_class" title="10.1.  Custom Class Mapping">custom class strategy</a>.
	You can also use OpenJPA's plugin format (see
	<a class="xref" href="ref_guide_conf_plugins.html" title="4.  Plugin Configuration">Section 4, “
	Plugin Configuration
	”</a>) to pass arguments to the
	strategy instance. See the
	<a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/strats/package-summary.html" target="_top">
	<code class="literal">org.apache.openjpa.jdbc.meta.strats</code></a> package for
	available strategies.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">SubclassStrategy</code>: The default mapping strategy for
	subclasses. You can specify a builtin strategy alias or the full class name of a
	<a class="link" href="ref_guide_mapping_custom.html#ref_guide_mapping_custom_class" title="10.1.  Custom Class Mapping"> custom class strategy</a>.
	You can also use OpenJPA's plugin format (see
	<a class="xref" href="ref_guide_conf_plugins.html" title="4.  Plugin Configuration">Section 4, “
	Plugin Configuration
	”</a>) to pass arguments to the
	strategy instance. Common strategies are <code class="literal">vertical</code> and
	<code class="literal">flat</code>, the default. See the
	<a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/strats/package-summary.html" target="_top">
	<code class="literal">org.apache.openjpa.jdbc.meta.strats</code></a> package for all
	available strategies.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">VersionStrategy</code>: The default version strategy for classes
	without a version field. You can specify a builtin strategy alias or the full
	class name of a <a class="link" href="ref_guide_mapping_custom.html#ref_guide_mapping_custom_versdiscrim" title="10.2.  Custom Discriminator and Version Strategies"> custom
	version strategy</a>. You can also use OpenJPA's plugin format (see
	<a class="xref" href="ref_guide_conf_plugins.html" title="4.  Plugin Configuration">Section 4, “
	Plugin Configuration
	”</a>) to pass arguments to the
	strategy instance. Common strategies are <code class="literal">none</code>, <code class="literal">
	state-comparison</code>, <code class="literal"> timestamp</code>, and <code class="literal">
	version-number</code>, the default. See the
	<a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/strats/package-summary.html" target="_top">
	<code class="literal">org.apache.openjpa.jdbc.meta.strats</code></a> package for all
	available strategies.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">DiscriminatorStrategy</code>: The default discriminator strategy
	when no discriminator value is given. You can specify a builtin strategy alias
	or the full class name of a
	<a class="link" href="ref_guide_mapping_custom.html#ref_guide_mapping_custom_versdiscrim" title="10.2.  Custom Discriminator and Version Strategies"> custom discriminator
	strategy</a>. You can also use OpenJPA's plugin format (see
	<a class="xref" href="ref_guide_conf_plugins.html" title="4.  Plugin Configuration">Section 4, “
	Plugin Configuration
	”</a>) to pass arguments to the
	strategy instance. Common strategies are <code class="literal">final</code> for a base
	class without subclasses, <code class="literal">none</code> to use joins to subclass
	tables rather than a discriminator column, and <code class="literal"> class-name</code>,
	the default. See the
	<a class="ulink" href="../javadoc/org/apache/openjpa/jdbc/meta/strats/package-summary.html" target="_top">
	<code class="literal">org.apache.openjpa.jdbc.meta.strats</code></a> package for all
	available strategies.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">FieldStrategies</code>: This property associates field types with
	custom strategies. The format of this property is similar to that of plugin
	strings (see <a class="xref" href="ref_guide_conf_plugins.html" title="4.  Plugin Configuration">Section 4, “
	Plugin Configuration
	”</a> ), without the class
	name. It is a comma-separated list of key/value pairs, where each key is a
	possible field type, and each value is itself a plugin string describing the
	strategy for that type. We present an example below. See
	<a class="xref" href="ref_guide_mapping_custom.html#ref_guide_mapping_custom_field" title="10.3.  Custom Field Mapping">Section 10.3, “
	Custom Field Mapping
	”</a> for information on custom
	field strategies.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">ForeignKeyDeleteAction</code>: The default delete action of foreign
	keys representing relations to other objects. Recognized values include
	<code class="literal">restrict</code>, <code class="literal">cascade</code>, <code class="literal">null</code>
	, <code class="literal">default</code>. These values correspond exactly to the standard
	database foreign key actions of the same names.
	</p>
	<p>
	The value <code class="literal">none</code> tells OpenJPA not to create database foreign
	keys on relation columns. This is the default.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">JoinForeignKeyDeleteAction</code>: The default delete action of
	foreign keys that join secondary, collection, map, or subclass tables to
	the primary table. Accepts the same values as the <code class="literal">
	ForeignKeyDeleteAction</code> property above.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">DeferConstraints</code>: Whether to use deferred database
	constraints if possible. Defaults to false.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">IndexLogicalForeignKeys</code>: Boolean property controlling
	whether to create indexes on logical foreign keys. Logical foreign keys are
	columns that represent a link between tables, but have been configured through
	the <code class="literal">ForeignKey</code> properties above not to use a physical
	database foreign key. Defaults to true.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">DataStoreIdColumnName</code>: The default name of datastore
	identity columns.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">DiscriminatorColumnName</code>: The default name of discriminator
	columns.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">IndexDiscriminator</code>: Whether to index the discriminator
	column. Defaults to true.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">VersionColumnName</code>: The default name of version columns.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">IndexVersion</code>: Whether to index the version column. Defaults
	to false.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">AddNullIndicator</code>: Whether to create a synthetic null
	indicator column for embedded mappings. The null indicator column allows OpenJPA
	to distinguish between a null embedded object and one with default values for
	all persistent fields.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">NullIndicatorColumnName</code>: The default name of synthetic null
	indicator columns for embedded objects.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">OrderLists</code>: Whether to create a database ordering column for
	maintaining the order of persistent lists and arrays.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">OrderColumnName</code>: The default name of collection and array
	ordering columns.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">StoreEnumOrdinal</code>: Set to true to store enum fields as
	numeric ordinal values in the database. The default is to store the enum value
	name as a string, which is more robust if the Java enum declaration might be
	rearranged.
	</p>
	</li><li class="listitem">
	<p>
	<code class="literal">StoreUnmappedObjectIdString</code>: Set to true to store the
	stringified identity of related objects when the declared related type is
	unmapped. By default, OpenJPA stores the related object's primary key value(s).
	However, this breaks down if different subclasses of the related type use
	incompatible primary key structures. In that case, stringifying the identity
	value is the better choice.
	</p>
	</li></ul></div>
	</li></ul></div>
	<p>
	The example below turns on foreign key generation during schema creation and
	associates the <code class="classname">org.mag.data.InfoStruct</code> field type with
	the custom <code class="classname">org.mag.mapping.InfoStructHandler</code> value
	handler.
	</p>
	<div class="example" id="ref_guide_mapping_defaults_conf"><p class="title"><b>Example 7.12.
	Configuring Mapping Defaults
	</b></p><div class="example-contents">

	<pre class="programlisting">
	<property name="openjpa.jdbc.MappingDefaults"
	value="ForeignKeyDeleteAction=restrict,
	FieldStrategies='org.mag.data.InfoStruct=org.mag.mapping.InfoStructHandler'"/>
	</pre>
	</div></div><br class="example-break">
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