Kraken JPA

Kraken JPA is based on hibernate 3 and provides declarative transaction feature.

Requirements

• kraken api 1.7.0
• slf4j api 1.5.6
• ipojo 1.4.0
• hibernate 3.3.0.SP1
• hibernate annotations 3.4.0.GA
• hibernate entity manager 3.4.0.GA
• hibernate commons annotations 3.3.0.GA
• hibernate c3p0 3.3.2.GA
• c3p0 0.9.1.2

Install

kraken> pkg.install kraken-jpa

Install JDBC Driver

kraken> jpa.installDriver
Database
-------------
[1] MySQL
[2] PostgreSQL
select? 1
Resolving com.mysql.jdbc/com.springsource.com.mysql.jdbc (5.1.6)
  -> trying to download from http://download.krakenapps.org/
bundle [18] loaded

POM Configuration

<Import-Package>
  javassist.util.proxy,
  org.hibernate.proxy,
  org.hibernate.exception,
  org.hibernate,
  org.hibernate.dialect,
  javax.persistence,*
</Import-Package>

• You MUST import above packages for JPA model bundle.
  • Otherwise, you will encounter HibernateProxy ClassNotFoundException.

iPOJO Handler Configuration

@JpaConfig(factory = "entityManagerFactoryName")
@Component(name = "example-component")
public class ExampleComponent {
    @Requires
    private ThreadLocalEntityManagerService entityManagerService;
}

• ThreadLocalEntityManagerService.getEntityManager() will return an EntityManager object in current thread context.
• entityManagerFactoryName is alias for JPA entity manager factory.

Database Configuration

• Kraken JPA recognizes two configuration files in bundle.
  • OSGI-INF/kraken-jpa/classes file have JPA entity classe names line by line.
  • OSGI-INF/kraken-jpa/config file contains hibernate configurations. (properties file format)
• You can load JPA entity bundle at kraken console.
  • "jpa.register [bundle id] [entity manager factory name]" script command will load above configuration files in specified bundle and create entity manager factory with configurations.
• You can also create entity manager factory programmatically.
  • Find the service reference for org.krakenapps.jpa.JpaService interface.
    • e.g. BundleContext.getServiceReference(JpaService.class.getName());

Configure C3P0 Properties

connection.provider_class = org.hibernate.connection.C3P0ConnectionProvider
hibernate.c3p0.min_size = 1
hibernate.c3p0.max_size = 100
hibernate.c3p0.timeout = 0
hibernate.c3p0.max_statements = 0

• connection.provider_class
  • For use C3P0, provider class must set org.hibernate.connection.C3P0ConnectionProvider.
• hibernate.c3p0.min_size
  • Minimum number of JDBC connections in the pool. (default: 1)
• hibernate.c3p0.max_size
  • Maximum number of JDBC connections in the pool. (default: 100)
• hibernate.c3p0.timeout
  • When an idle connection is removed from the pool (in second). (default: 0 (never expire))
• hibernate.c3p0.max_statements
  • Number of prepared statements will be cached. Increase performance. (default: 0)

Declarative Transaction Support

• @Transactional method annotation provides declarative transaction feature.
  • ThreadLocalEntityManagerService will begin transaction at method entry and commit transaction at method exit. If any error occured, transaction will be rollbacked. Finally, the EntityManager object closed.
• TransactionOption (from 1.1.0 release)
  • @Transactional has TransactionOption.Required by default.
  • TransactionOption.Required: Shares a transaction, if one exists, and creates a new transaction if necessary.
  • TransactionOption.RequiresNew: Executes the method with a new transaction, regardless of the state of the current context.
  • TransactionOption.Supported: Shares a transaction, if one exists.

Kraken JPA Script

• jpa.list: list all registered entity manager factories.
• jpa.register [bundle id] [entity manager factory name]: load configuration from specified bundle and register entity manager factory.
• jpa.unregister [entity manager factory name]: unregister and close entity manager factory.

Kraken JPA Class Diagram

History

• 1.5.0 release
  • Added C3P0 Connection Provider.
• 1.4.0 release
  • Upgraded to JPA 2.0 and Hibernate 3.5.4 Final.
  • Added connection validation for JPA model registration process.
• 1.1.1 release: Fixed handler validation bug at boot time.
• 1.1.0 release: Added TransactionOption to @Transactional. Nested @Transactional declaration is supported.
• 1.0.0 release: Implemented using hibernate.