Overriding metadata through XML.1.2. Entity level metadata

Overriding metadata through XML.1.2. Entity level metadata

You can either define or override metadata informations on a given entity. 

<?xml version="1.0" encoding="UTF-8"?>

<entity-mappings 
  xmlns="http://java.sun.com/xml/ns/persistence/orm"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm orm_1_0.xsd"
  version="1.0">

    <package>org.hibernate.test.reflection.java.xml</package>
    <entity class="Administration" access="PROPERTY" metadata-complete="true">
        <table name="tbl_admin">
            <unique-constraint>
                <column-name>firstname</column-name>
                <column-name>lastname</column-name>
            </unique-constraint>
        </table>
        <secondary-table name="admin2">
            <primary-key-join-column name="admin_id" referenced-column-name="id"/>
            <unique-constraint>
                <column-name>address</column-name>
            </unique-constraint>
        </secondary-table>
        <id-class class="SocialSecurityNumber"/>
        <inheritance strategy="JOINED"/>
        <sequence-generator name="seqhilo" sequence-name="seqhilo"/>
        <table-generator name="table" table="tablehilo"/>
        ...
    </entity>

    <entity class="PostalAdministration">
        <primary-key-join-column name="id"/>
        ...
    </entity>
</entity-mappings>
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entity-mappings: entity-mappings is the root element for all XML files. You must declare the xml schema, the schema file is included in the hibernate-annotations.jar file, no internet access will be processed by Hibernate Annotations.

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package (optional): default package used for all non qualified class names in the given deployment descriptor file.

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entity: desribes an entity.

metadata-complete defines whether the metadata description for this element is complete or not (in other words, if annotations present at the class level should be considered or not).

An entity has to have a class attribute refering the java class the metadata applies on.

You can overrides entity name through the name attribute, if none is defined and if an @Entity.name is present, then it is used (provided that metadata complete is not set).

For netadata complete (see below) element, you can define an access (either FIELD or PROPERTY (default)). For non medatada complete element, if access is not defined, the @Id position will lead position, if access is defined, the value is used.

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table: you can declare table properties (name, schema, catalog), if none is defined, the java annotation is used.

You can define one or several unique constraints as seen in the example

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secondary-table: defines a secondary table very much like a regular table except that you can define the primary key / foreign key column(s) through the primary-key-join-column element. On non metadata complete, annotation secondary tables are used only if there is no secondary-table definition, annotations are ignored otherwise.

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id-class: defines the id class in a similar way @IdClass does

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inheritance: defines the inheritance strategy (JOINED, TABLE_PER_CLASS, SINGLE_TABLE), Available only at the root entity level

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sequence-generator: defines a sequence generator

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table-generator: defines a table generator

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primary-key-join-column: defines the primary key join column for sub entities when JOINED inheritance strategy is used 

<?xml version="1.0" encoding="UTF-8"?>

<entity-mappings 
  xmlns="http://java.sun.com/xml/ns/persistence/orm"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm orm_1_0.xsd"
  version="1.0">

    <package>org.hibernate.test.reflection.java.xml</package>
    <entity class="Music" access="PROPERTY" metadata-complete="true">
        <discriminator-value>Generic</discriminator-value>
        <discriminator-column length="34"/>
        ...
    </entity>

    <entity class="PostalAdministration">
        <primary-key-join-column name="id"/>
        <named-query name="adminById">
            <query>select m from Administration m where m.id = :id</query>
            <hint name="org.hibernate.timeout" value="200"/>
        </named-query>
        <named-native-query name="allAdmin" result-set-mapping="adminrs">
            <query>select *, count(taxpayer_id) as taxPayerNumber 
            from Administration, TaxPayer
            where taxpayer_admin_id = admin_id group by ...</query>
            <hint name="org.hibernate.timeout" value="200"/>
        </named-native-query>
        <sql-result-set-mapping name="adminrs">
            <entity-result entity-class="Administration">
                <field-result name="name" column="fld_name"/>
            </entity-result>
            <column-result name="taxPayerNumber"/>
        </sql-result-set-mapping>
        <attribute-override name="ground">
            <column name="fld_ground" unique="true" scale="2"/>
        </attribute-override>
        <association-override name="referer">
            <join-column name="referer_id" referenced-column-name="id"/>
        </association-override>
        ...
    </entity>
</entity-mappings>
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discriminator-value / discriminator-column: defines the discriminator value and the column holding it when the SINGLE_TABLE inheritance strategy is chosen

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named-query: defines named queries and possibly the hints associated to them. Those definitions are additive to the one defined in annotations, if two definitions have the same name, the XML one has priority.

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named-native-query: defines an named native query and its sql result set mapping. Alternatively, you can define the result-class. Those definitions are additive to the one defined in annotations, if two definitions have the same name, the XML one has priority.

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sql-result-set-mapping: describes the result set mapping structure. You can define both entity and column mappings. Those definitions are additive to the one defined in annotations, if two definitions have the same name, the XML one has priority

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attribute-override / association-override: defines a column or join column overriding. This overriding is additive to the one defined in annotations

Same applies for <embeddable> and <mapped-superclass>.