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Documentation for Parameterized Types

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git-svn-id: https://svn.jboss.org/repos/hibernate/trunk/Hibernate3/doc@5145 1b8cb986-b30d-0410-93ca-fae66ebed9b2
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Michael Gloegl 2005-01-11 00:18:05 +00:00
parent 40ca8fe193
commit 0f09e4a289
1 changed files with 36 additions and 1 deletions
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reference/en/modules/basic_mapping.xml
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@ -2291,7 +2291,7 @@
</sect2>
<sect2 id="mapping-types-custom">
<sect2 id="mapping-types-custom" revision="2">
<title>Custom value types</title>
<para>
@ -2322,6 +2322,41 @@
Notice the use of <literal>&lt;column&gt;</literal> tags to map a property to multiple
columns.
</para>
<para>
You may also supply parameters to a UserType in the mapping file. To do this, your UserType
has to implement the <literal>org.hibernate.usertype.ParameterizedType</literal> interface.
To supply parameters to your UserType, you can use the <literal>&lt;type&gt;</literal> element
in your mapping files.
</para>
<programlisting><![CDATA[<property name="primitiveWithNullValues" column="INT_COLUMN">
<type name="org.hibernate.test.typeparameters.NullMappingType">
<param name="default">1</param>
</type>
</property>]]></programlisting>
<para>
The UserType can now retrieve the value for the parameter named <literal>default</literal>
from the Properties object passed to it.
</para>
<para>
If you use a certain UserType very often, it may be useful to define a shorter name for it.
You can do this using the <literal>&lt;typedef&gt;</literal> element in your mapping files.
Typedefs contain a UserType and a defined name for it, and may also contain a list of default
paramter values if the type defined implements <literal>ParameterizedType</literal>. After
defining the name, it can be used everywhere the original classname can be used.
</para>
<programlisting><![CDATA[<typedef class="org.hibernate.test.typeparameters.NullMappingType" name="nullMapper">
<param name="default">2</param>
</typedef>
<property name="primitiveWithNullValues" column="INT_COLUMN">
<type name="nullMapper"/>
</property>]]></programlisting>
<para>
It is also possible to override the parameters supplied in a typedef on a case-by-case basis
by using type parameters on the property mapping.
</para>
<para>
Even though Hibernate's rich range of built-in types and support for components means you
will very rarely <emphasis>need</emphasis> to use a custom type, it is nevertheless