As in persistence metadata, mapping metadata uses the class element and its name attribute to identify persistent classes. Mapping metadata, however, expands the class element with the table attribute.

The table attribute specifies the name of the table whose rows represent instances of this class. If the table is in a non-default schema, you can specify this attribute as <schema-name>.<table-name>. This attribute is optional, because not all classes must be mapped to unique tables. We explore the mapping of classes to tables in more depth in Section 15.8, “Inheritance”.

Sometimes, some of the fields in a class are mapped to secondary tables. In that case, use the class' table attribute to name what you consider the class' primary table. Later, we will see how to map certain fields to other tables.

The example below maps classes to tables according to the following diagram. Note that the abstract Contract class is left unmapped. The SUB, TRIAL_SUB, and LINE_ITEM tables are in the CNTRCT schema; all other tables are in the default schema.

Note that the example does not include our model's Address class in the mapping metadata document. In Chapter 5, Metadata, we defined Address as an embedded only class. That means that Address instances are only stored as part of other records; therefore Address does not have its own mapping.

<?xml version="1.0"?>
<orm>
    <package name="org.mag">
        <sequence name="ArticleSeq" datastore-sequence="ART_SEQ"/> 
        <class name="Magazine" table="MAG">
            ...
        </class>
        <class name="Article" table="ART">
            ...
        </class>    
    </package>
    <package name="org.mag.pub">
        <sequence name="AuthorSeq" factory-class="Author$SequenceFactory"/>
        <class name="Company" table="COMP">
            ...
        </class>    
        <class name="Author" table="AUTH">
            ...
        </class>
    </package>
    <package name="org.mag.subscribe">
        <sequence name="ContractSeq" strategy="transactional"/> 
        <class name="Contract">
            ...
        </class>
        <class name="Subscription" table="CNTRCT.SUB">
            ...
        </class>
        <class name="LifetimeSubscription">
            ...
        </class>
        <class name="TrialSubscription" table="CNTRCT.TRIAL_SUB">
            ...
        </class>
        <class name="Subscription$LineItem" table="CNTRCT.LINE_ITEM">
            ...
        </class>
    </package>
</orm>