Hi,
Since the release of JDK 9 is behind the corner, it would be good to
update the spec to be ready for it.
I can see 2 things which can be done:
1) JPA_SPEC-145: define module name
I'm not 100% sure this needs to be done but for the sake of completeness
- it is clear that the module name should be 'java.persistence'. While
it would be nice to have the name defined and available, do we really
need this or should we stick with API being resolved on JDK9 as an
automatic module?
I'm proposing to NOT touch this area in the spec now and keep this up to
the provider. Any opinions?
2) JPA_SPEC-146: Use ServiceLoader facility
with the introduction of the module system there are currently 2 ways,
how persistence provider implementation can be defined -
META-INF/services and module-info with 'provides ... with...'. Former
way is already covered but the latter is not, so I'd like to propose
following change to Section 9.2 of the spec (additions are in italics,
removals are striked-through italics)
*Section 9.2 Bootstrapping in Java SE Environments*
In Java SE environments, the Persistence.createEntityManagerFactory
method is used
by the application to create an entity manager factory.
A persistence provider implementation running in a Java SE environment
should also act as a service
provider by supplying a service provider configuration /file as
described in the JAR File Specification/. /The Persistence//
//bootstrap class should use ServiceLoader facility to locate all
available provider implementations./
The provider configuration /file/ serves to export the provider
implementation class to the Persistence
bootstrap class, positioning the provider as a candidate for backing
named persistence units.
The provider may supply the provider configuration file by creating a
text file named javax.persistence.spi.PersistenceProvider
and placing it in the META-INF/services directory of
one of its JAR files. The contents of the file should be the name of the
provider implementation class of
the javax.persistence.spi.PersistenceProvider interface.
Example/1/:
A persistence vendor called ACME persistence products ships a JAR called
acme.jar that contains
its persistence provider implementation. The JAR includes the provider
configuration file.
acme.jar
META-INF/services/javax.persistence.spi.PersistenceProvider
com.acme.PersistenceProvider
…
The contents of the
META-INF/services/javax.persistence.spi.PersistenceProvider
file is nothing more than the name of the implementation class:
com.acme.PersistenceProvider.
/Example 2://
//A persistence vendor called ACME persistence products ships a module
called acme.jar that provides persistence provider implementation. The
JAR contains module definition which contains the name of the
implementation class.//
//
//acme.jar//
// module-info.class//
// …//
//
//module acme {//
// provides javax.persistence.spi.PersistenceProvider with
com.acme.PersistenceProvider;//
// …//
//}//
//
//The source code of the provider's module definition must contain the
name of the provider’s implementation class./
Persistence provider jars may be installed or made available in the same
ways as other service providers,
e.g. as extensions/,/or added to the application classpath according to
the guidelines in the JAR File
Specification /or added to the application module path according to the
guidelines in the Java Platform Module System specification/./
/
Do you think this is fine, something should be corrected or is there a
reason why this second part should not be added to JPA 2.2 MR?
Thank you,
--lukas
[1]:
https://java.net/jira/browse/JPA_SPEC-145
[2]:
https://java.net/jira/browse/JPA_SPEC-146