Chapter 6. Persistence
Table of Contents
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Note
OpenJPA also includes the
OpenJPAPersistence helper class to provide
additional utility methods.
Within a container, you will typically use injection to
access an EntityManagerFactory. Applications operating
outside of a container, however, can use the
Persistence class to obtain
EntityManagerFactory objects in a vendor-neutral fashion.
public static EntityManagerFactory createEntityManagerFactory(String name); public static EntityManagerFactory createEntityManagerFactory(String name, Map props); public static PersistenceUtil getPersistenceUtil();
Each createEntityManagerFactory method searches the
system for an EntityManagerFactory definition with the
given name. Use null for an unnamed factory. The optional map
contains vendor-specific property settings used to further configure the
factory.
persistence.xml files define
EntityManagerFactories. The createEntityManagerFactory
methods search for persistence.xml files
within the META-INF directory of any CLASSPATH
element. For example, if your CLASSPATH contains
the conf directory, you could place an
EntityManagerFactory definition in
conf/META-INF/persistence.xml.
The getPersistenceUtil method returns a PersistenceUtil
interface that can be used to determine whether an entity or attribute of an
entity is loaded.
PersistenceUtil pUtil = Persistence.getPersistenceUtil();
if (!pUtil.isLoaded(myEntity)) {
loadEntity(myEntity);
}
1. persistence.xml
With the introduction of JPA 2.0, there are two versions of the
persistence.xml. The most current revision of the
2.0 persistence schema is presented below. Version 1.0 of the persistence
schema can be found at
http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd.
<?xml version="1.0" encoding="UTF-8"?>
<!-- persistence.xml schema -->
<xsd:schema targetNamespace="http://java.sun.com/xml/ns/persistence"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:persistence="http://java.sun.com/xml/ns/persistence"
elementFormDefault="qualified" attributeFormDefault="unqualified"
version="2.0">
<xsd:annotation>
<xsd:documentation>
@(#)persistence_2_0.xsd 1.0 October 1 2009
</xsd:documentation>
</xsd:annotation>
<xsd:annotation>
<xsd:documentation>
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option by the copyright holder.
</xsd:documentation>
</xsd:annotation>
<xsd:annotation>
<xsd:documentation>
<![CDATA[
This is the XML Schema for the persistence configuration file.
The file must be named "META-INF/persistence.xml" in the
persistence archive.
Persistence configuration files must indicate
the persistence schema by using the persistence namespace:
http://java.sun.com/xml/ns/persistence
and indicate the version of the schema by
using the version element as shown below:
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
...
</persistence>
]]>
</xsd:documentation>
</xsd:annotation>
<xsd:simpleType name="versionType">
<xsd:restriction base="xsd:token">
<xsd:pattern value="[0-9]+(\.[0-9]+)*" />
</xsd:restriction>
</xsd:simpleType>
<!-- **************************************************** -->
<xsd:element name="persistence">
<xsd:complexType>
<xsd:sequence>
<!-- **************************************************** -->
<xsd:element name="persistence-unit"
minOccurs="1" maxOccurs="unbounded">
<xsd:complexType>
<xsd:annotation>
<xsd:documentation>
Configuration of a persistence unit.
</xsd:documentation>
</xsd:annotation>
<xsd:sequence>
<!-- **************************************************** -->
<xsd:element name="description"
type="xsd:string" minOccurs="0">
<xsd:annotation>
<xsd:documentation>
Description of this persistence unit.
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<!-- **************************************************** -->
<xsd:element name="provider"
type="xsd:string" minOccurs="0">
<xsd:annotation>
<xsd:documentation>
Provider class that supplies EntityManagers for this
persistence unit.
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<!-- **************************************************** -->
<xsd:element name="jta-data-source"
type="xsd:string" minOccurs="0">
<xsd:annotation>
<xsd:documentation>
The container-specific name of the JTA datasource to use.
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<!-- **************************************************** -->
<xsd:element name="non-jta-data-source"
type="xsd:string" minOccurs="0">
<xsd:annotation>
<xsd:documentation>
The container-specific name of a non-JTA datasource to use.
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<!-- **************************************************** -->
<xsd:element name="mapping-file"
type="xsd:string" minOccurs="0"
maxOccurs="unbounded">
<xsd:annotation>
<xsd:documentation>
File containing mapping information. Loaded as a resource
by the persistence provider.
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<!-- **************************************************** -->
<xsd:element name="jar-file"
type="xsd:string" minOccurs="0"
maxOccurs="unbounded">
<xsd:annotation>
<xsd:documentation>
Jar file that is to be scanned for managed classes.
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<!-- **************************************************** -->
<xsd:element name="class" type="xsd:string"
minOccurs="0" maxOccurs="unbounded">
<xsd:annotation>
<xsd:documentation>
Managed class to be included in the persistence unit and
to scan for annotations. It should be annotated
with either @Entity, @Embeddable or @MappedSuperclass.
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<!-- **************************************************** -->
<xsd:element name="exclude-unlisted-classes"
type="xsd:boolean" default="true"
minOccurs="0">
<xsd:annotation>
<xsd:documentation>
When set to true then only listed classes and jars will
be scanned for persistent classes, otherwise the
enclosing jar or directory will also be scanned.
Not applicable to Java SE persistence units.
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<!-- **************************************************** -->
<xsd:element name="shared-cache-mode"
type="persistence:persistence-unit-caching-type"
minOccurs="0">
<xsd:annotation>
<xsd:documentation>
Defines whether caching is enabled for the
persistence unit if caching is supported by the
persistence provider. When set to ALL, all entities
will be cached. When set to NONE, no entities will
be cached. When set to ENABLE_SELECTIVE, only entities
specified as cacheable will be cached. When set to
DISABLE_SELECTIVE, entities specified as not cacheable
will not be cached. When not specified or when set to
UNSPECIFIED, provider defaults may apply.
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<!-- **************************************************** -->
<xsd:element name="validation-mode"
type="persistence:persistence-unit-validation-mode-type"
minOccurs="0">
<xsd:annotation>
<xsd:documentation>
The validation mode to be used for the persistence unit.
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<!-- **************************************************** -->
<xsd:element name="properties"
minOccurs="0">
<xsd:annotation>
<xsd:documentation>
A list of standard and vendor-specific properties
and hints.
</xsd:documentation>
</xsd:annotation>
<xsd:complexType>
<xsd:sequence>
<xsd:element name="property"
minOccurs="0" maxOccurs="unbounded">
<xsd:annotation>
<xsd:documentation>
A name-value pair.
</xsd:documentation>
</xsd:annotation>
<xsd:complexType>
<xsd:attribute
name="name" type="xsd:string"
use="required" />
<xsd:attribute
name="value" type="xsd:string"
use="required" />
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
<!-- **************************************************** -->
<xsd:attribute name="name" type="xsd:string"
use="required">
<xsd:annotation>
<xsd:documentation>
Name used in code to reference this persistence unit.
</xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<!-- **************************************************** -->
<xsd:attribute name="transaction-type"
type="persistence:persistence-unit-transaction-type">
<xsd:annotation>
<xsd:documentation>
Type of transactions used by EntityManagers from this
persistence unit.
</xsd:documentation>
</xsd:annotation>
</xsd:attribute>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
<xsd:attribute name="version" type="persistence:versionType"
fixed="2.0" use="required" />
</xsd:complexType>
</xsd:element>
<!-- **************************************************** -->
<xsd:simpleType name="persistence-unit-transaction-type">
<xsd:annotation>
<xsd:documentation>
public enum PersistenceUnitTransactionType {JTA, RESOURCE_LOCAL};
</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:token">
<xsd:enumeration value="JTA" />
<xsd:enumeration value="RESOURCE_LOCAL" />
</xsd:restriction>
</xsd:simpleType>
<!-- **************************************************** -->
<xsd:simpleType name="persistence-unit-caching-type">
<xsd:annotation>
<xsd:documentation>
public enum SharedCacheMode { ALL, NONE, ENABLE_SELECTIVE,
DISABLE_SELECTIVE, UNSPECIFIED};
</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:token">
<xsd:enumeration value="ALL" />
<xsd:enumeration value="NONE" />
<xsd:enumeration value="ENABLE_SELECTIVE" />
<xsd:enumeration value="DISABLE_SELECTIVE" />
<xsd:enumeration value="UNSPECIFIED" />
</xsd:restriction>
</xsd:simpleType>
<!-- **************************************************** -->
<xsd:simpleType name="persistence-unit-validation-mode-type">
<xsd:annotation>
<xsd:documentation>
public enum ValidationMode { AUTO, CALLBACK, NONE};
</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:token">
<xsd:enumeration value="AUTO" />
<xsd:enumeration value="CALLBACK" />
<xsd:enumeration value="NONE" />
</xsd:restriction>
</xsd:simpleType>
</xsd:schema>
The root element of a persistence.xml file is
persistence, which then contains one or more
persistence-unit definitions. The root element should include the
version attribute with the appropriate version, 1.0 for a
version 1.0 file and 2.0 for a version 2.0 file. Each
persistence unit describes the configuration for the entity managers created by
the persistence unit's entity manager factory. The persistence unit can specify
these elements and attributes.
-
name: This is the name you pass to thePersistence.createEntityManagerFactorymethods described above. The name attribute is required. -
transaction-type: Whether to use managed (JTA) or local (RESOURCE_LOCAL) transaction management. -
provider: If you are using a third-party JPA vendor, this element names its implementation of thePersistenceProviderbootstrapping interface.Note
Set the
providertoorg.apache.openjpa.persistence.PersistenceProviderImplto use OpenJPA. -
jta-data-source: The JNDI name of a JDBCDataSourcethat is automatically enlisted in JTA transactions. This may be an XADataSource. -
non-jta-data-source: The JNDI name of a JDBCDataSourcethat is not enlisted in JTA transactions. -
mapping-file*: The resource names of XML mapping files for entities and embeddable classes. You can also specify mapping information in anorm.xmlfile in yourMETA-INFdirectory. If present, theorm.xmlmapping file will be read automatically. -
jar-file*: The names of jar files containing entities and embeddable classes. The implementation will scan the jar for annotated classes. -
class*: The class names of entities and embeddable classes. -
properties: This element contains nestedpropertyelements used to specify vendor-specific settings. Eachpropertyhas a name attribute and a value attribute.Note
The Reference Guide's Chapter 2, Configuration describes OpenJPA's configuration properties.
Here is a typical persistence.xml file for a non-EE
environment:
Example 6.1. persistence.xml
<?xml version="1.0"?>
<persistence version="1.0">
<persistence-unit name="openjpa">
<provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider>
<class>tutorial.Animal</class>
<class>tutorial.Dog</class>
<class>tutorial.Rabbit</class>
<class>tutorial.Snake</class>
<properties>
<property name="openjpa.ConnectionURL" value="jdbc:hsqldb:tutorial_database"/>
<property name="openjpa.ConnectionDriverName" value="org.hsqldb.jdbcDriver"/>
<property name="openjpa.ConnectionUserName" value="sa"/>
<property name="openjpa.ConnectionPassword" value=""/>
<property name="openjpa.Log" value="DefaultLevel=WARN, Tool=INFO"/>
</properties>
</persistence-unit>
</persistence>