In a Java EE 6 application where I'm using .ear packaging, I'd like to create a persistence unit that can be accessed from components in different .jar files.
However, I'm not sure how to define this persistence unit. With the @PersistenceContext annotation the lookup only succeeds if the name matches a persistence unit defined in the local persistence.xml file.
Is it possible to refer to external persistence units?
The JAR file or directory whose META-INF directory contains persistence. xml is called the root of the persistence unit. The scope of the persistence unit is determined by the persistence unit's root.
xml should be located in the WAR file's WEB-INF/classes/META-INF directory. If you package the persistence unit in a JAR file that will be included in a WAR or EAR file, the JAR file should be located: In the WEB-INF/lib directory of a WAR. In the EAR file's library directory.
xml file. This file defines a persistence unit named OrderManagement, which uses a JTA-aware data source jdbc/MyOrderDB. The jar-file and class elements specify managed persistence classes: entity classes, embeddable classes, and mapped superclasses.
The persistence. xml configuration file is used to configure a given JPA Persistence Unit. The Persistence Unit defines all the metadata required to bootstrap an EntityManagerFactory , like entity mappings, data source, and transaction settings, as well as JPA provider configuration properties.
Here are the relevant sections of the JPA 2.0 specification:
8.2 Persistence Unit Packaging
...
A persistence unit is defined by a
persistence.xml
file. The jar file or directory whoseMETA-INF
directory contains thepersistence.xml
file is termed the root of the persistence unit. In Java EE environments, the root of a persistence unit must be one of the following:
- an EJB-JAR file
- the WEB-INF/classes directory of a WAR file[80]
- a jar file in the WEB-INF/lib directory of a WAR file
- a jar file in the EAR library directory
- an application client jar file
It is not required that an EJB-JAR or WAR file containing a persistence unit be packaged in an EAR unless the persistence unit contains persistence classes in addition to those contained within the EJB-JAR or WAR. See Section 8.2.1.6.
NOTE: Java Persistence 1.0 supported use of a jar file in the root of the EAR as the root of a persistence unit. This use is no longer supported. Portable applications should use the EAR library directory for this case instead. See [9].
A persistence unit must have a name. Only one persistence unit of any given name must be defined within a single EJB-JAR file, within a single WAR file, within a single application client jar, or within an EAR. See Section 8.2.2, “Persistence Unit Scope”.
The
persistence.xml
file may be used to designate more than one persistence unit within the same scope.All persistence classes defined at the level of the Java EE EAR must be accessible to all other Java EE components in the application - i.e. loaded by the application classloader - such that if the same entity class is referenced by two different Java EE components (which may be using different persistence units), the referenced class is the same identical class.
And later:
8.2.2 Persistence Unit Scope
An EJB-JAR, WAR, application client jar, or EAR can define a persistence unit.
When referencing a persistence unit using the
unitName
annotation element orpersistence-unit-name
deployment descriptor element, the visibility scope of the persistence unit is determined by its point of definition:
- A persistence unit that is defined at the level of an EJB-JAR, WAR, or application client jar is scoped to that EJB-JAR, WAR, or application jar respectively and is visible to the components defined in that jar or war.
- A persistence unit that is defined at the level of the EAR is generally visible to all components in the application. However, if a persistence unit of the same name is defined by an EJB-JAR, WAR, or application jar file within the EAR, the persistence unit of that name defined at EAR level will not be visible to the components defined by that EJB-JAR, WAR, or application jar file unless the persistence unit reference uses the persistence unit name
#
syntax to specify a path name to disambiguate the reference. When the#
syntax is used, the path name is relative to the referencing application component jar file. For example, the syntax../lib/persistenceUnitRoot.jar#myPersistenceUnit
refers to a persistence unit whose name, as specified in the name element of thepersistence.xml
file, ismyPersistenceUnit
and for which the relative path name of the root of the persistence unit is../lib/persistenceUnitRoot.jar
. The#
syntax may be used with both theunitName
annotation element orpersistence-unit-name
deployment descriptor element to reference a persistence unit defined at EAR level.Also you need to include entity classes jar in manifest of pu jar http://wiki.eclipse.org/Packaging_and_Deploying_EclipseLink_JPA_Applications_(ELUG)
To summarize, you should be able to define your entities and the persistence unit at the top level of the EAR and to use them from the other modules.
I'm just not sure to understand what you tried and what problem(s) you faced.
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