EclipseLink/Examples/JPA/Dynamic

How to use Dynamic EclipseLink JPA

EclipseLink JPA supports Dynamic Persistence allowing users to map relational tables to virtual classes which are created dynamically at runtime. This support was added in EclipseLink 2.1.0. This example illustrates dynamic persistence using the DynamicEntity interface for all of the persistent types.

Configuration

With dynamic persistence the mappings and implied entity types can be defined using API within the application code or they can be specified using the eclipselink-orm.xml mapping file.

eclipselink-orm.xml

There are a couple of key differences versus a standard JPA mapping file:

• access type of VIRTUAL is used
• attribute-type must be provided

<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings version="2.1"
	xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/orm"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 
	<package>example.jpa.dynamic.model.employee</package>
 
	<object-type-converter name="gender-converter"
		object-type="String" data-type="String">
		<conversion-value object-value="Male" data-value="M" />
		<conversion-value object-value="Female" data-value="F" />
	</object-type-converter>
 
	<named-query name="Employee.findAll">
		<query>SELECT e FROM Employee e ORDER BY e.lastName, e.firstName</query>
		<hint name="eclipselink.query-results-cache" value="True" />
	</named-query>
 
	<named-query name="Employee.findMin">
		<query>SELECT e FROM Employee e WHERE e.id IN (SELECT MIN(ee.id) FROM
			Employee ee)</query>
	</named-query>
 
	<entity class="Address" access="VIRTUAL">
		<attributes>
			<id name="id" attribute-type="Integer">
				<column name="ADDRESS_ID" />
				<generated-value strategy="SEQUENCE" generator="address-generator" />
				<sequence-generator name="address-generator"
					sequence-name="ADDR_SEQ" />
			</id>
			<basic name="city" attribute-type="String" />
			<basic name="country" attribute-type="String" />
			<basic name="province" attribute-type="String" />
			<basic name="postalCode" attribute-type="String">
				<column name="P_CODE" />
			</basic>
			<basic name="street" attribute-type="String" />
		</attributes>
	</entity>
 
	<entity class="PhoneNumber" access="VIRTUAL">
		<table name="PHONE" />
		<attributes>
			<id name="id" attribute-type="Integer">
				<column name="PHONE_NUM_ID" />
				<generated-value strategy="SEQUENCE" />
			</id>
			<basic name="type" attribute-type="String">
				<column updatable="false" />
			</basic>
			<basic name="areaCode" attribute-type="String">
				<column name="AREA_CODE" />
			</basic>
			<basic name="number" attribute-type="String">
				<column name="P_NUMBER" />
			</basic>
			<many-to-one name="owner" fetch="EAGER" target-entity="Employee">
				<join-column name="EMP_ID" />
			</many-to-one>
		</attributes>
	</entity>
 
	<entity class="Employee" access="VIRTUAL">
		<secondary-table name="SALARY" />
		<attributes>
			<id name="id" attribute-type="Integer">
				<column name="EMP_ID" />
				<generated-value strategy="SEQUENCE" generator="employee-generator" />
				<sequence-generator name="employee-generator"
					sequence-name="EMP_SEQ" />
			</id>
			<basic name="firstName" attribute-type="String">
				<column name="F_NAME" />
			</basic>
			<basic name="lastName" attribute-type="String">
				<column name="L_NAME" />
			</basic>
			<basic name="startTime" attribute-type="String">
				<column name="START_TIME" />
			</basic>
			<basic name="endTime" attribute-type="String">
				<column name="END_TIME" />
			</basic>
			<basic name="gender" attribute-type="String">
				<column name="GENDER" />
				<convert>gender-converter</convert>
			</basic>
			<basic name="salary" attribute-type="Integer">
				<column table="SALARY" />
			</basic>
 
			<version name="version" attribute-type="Long" />
 
			<many-to-one name="manager" fetch="EAGER" optional="true"
				target-entity="Employee">
				<join-column name="MANAGER_ID" />
			</many-to-one>
 
			<one-to-many name="managedEmployees" mapped-by="manager"
				target-entity="Employee" attribute-type="java.util.List" />
 
			<one-to-many name="phoneNumbers" mapped-by="owner"
				target-entity="PhoneNumber" attribute-type="java.util.List">
				<cascade>
					<cascade-all />
				</cascade>
				<private-owned />
			</one-to-many>
 
			<one-to-one name="address" fetch="EAGER" target-entity="Address">
				<join-column name="ADDR_ID" />
				<cascade>
					<cascade-all />
				</cascade>
				<private-owned />
			</one-to-one>
 
			<many-to-many name="projects" target-entity="Project"
				attribute-type="java.util.List">
				<join-table name="PROJ_EMP">
					<join-column name="EMP_ID" />
					<inverse-join-column name="PROJ_ID" />
				</join-table>
			</many-to-many>
 
			<element-collection name="responsibilities"
				attribute-type="java.util.List" target-class="String">
				<column name="RESPON_DESC" />
				<collection-table name="RESPONS" />
			</element-collection>
 
			<embedded name="period" attribute-type="EmploymentPeriod" />
 
		</attributes>
	</entity>
 
	<entity class="Project" access="VIRTUAL">
		<inheritance strategy="JOINED" />
		<discriminator-column name="PROJ_TYPE"
			discriminator-type="CHAR" />
		<attributes>
			<id name="id" attribute-type="Integer">
				<column name="PROJ_ID" />
				<generated-value strategy="SEQUENCE" generator="project-generator" />
				<sequence-generator name="project-generator"
					sequence-name="PROJ_SEQ" />
			</id>
			<basic name="description" attribute-type="String">
				<column name="DESCRIP" />
			</basic>
			<basic name="name" attribute-type="String">
				<column name="PROJ_NAME" />
			</basic>
			<version name="version" attribute-type="Long" />
			<many-to-one name="teamLeader" fetch="EAGER"
				target-entity="Employee">
				<join-column name="LEADER_ID" />
			</many-to-one>
		</attributes>
	</entity>
 
	<entity class="SmallProject" parent-class="Project" access="VIRTUAL">
		<table name="PROJECT" />
		<discriminator-value>S</discriminator-value>
	</entity>
 
	<entity class="LargeProject" parent-class="Project" access="VIRTUAL">
		<table name="LPROJECT" />
		<discriminator-value>L</discriminator-value>
		<attributes>
			<basic name="budget" attribute-type="Double" />
			<basic name="milestone" attribute-type="java.util.Calendar">
				<temporal>TIMESTAMP</temporal>
			</basic>
		</attributes>
	</entity>
 
	<embeddable class="EmploymentPeriod" access="VIRTUAL">
		<attributes>
			<basic name="startDate" attribute-type="java.util.Date">
				<column name="START_DATE" />
				<temporal>DATE</temporal>
			</basic>
			<basic name="endDate" attribute-type="java.util.Date">
				<column name="END_DATE" />
				<temporal>DATE</temporal>
			</basic>
		</attributes>
	</embeddable>
 
</entity-mappings>

Usage Examples

Bootstrap

In order to bootstrap with dynamic persistence some additional persistence unit properties must be specified.

Note: Container managed persistence not supported

        Map<String, Object> properties = new HashMap<String, Object>();
        ExamplePropertiesLoader.loadProperties(properties);
        properties.put(PersistenceUnitProperties.CLASSLOADER, dcl);
        properties.put(PersistenceUnitProperties.WEAVING, "static");
        return Persistence.createEntityManagerFactory(persistenceUnit, properties);