Apache Karaf JPA Example

Abstract

This example shows how to use JPA with an entity. The entity manager is used in the persistence implementation.

It implements a BookingService similar using a database for the storage, with a JPA entity.

This example uses blueprint and declarative service to deal with JPA entity manager.

The “command” bundle uses the BookingService.

Artifacts

• karaf-jpa-example-provider module contain:
  • karaf-jpa-example-api is a bundle providing the Booking entity used in the BookingService. As a best practice, this bundle should use a common bundle containing the BookingService interface, and then wrapping Booking POJO as a JpaBooking entity for instance. For convenience and reduce the number of example artifacts, we gather interface and implementation in the same bundle (again, it's bad).
  • karaf-jpa-example-provider-blueprint contain bundles providing EclipseLink and Hibernate implementation using blueprint.
  • karaf-jpa-example-provider-ds contain bundles providing EclipseLink and Hibernate implementation using declarative service.
• karaf-jpa-example-command provides shell command to manipulate the BookingService. It use declarative service to retreive one instance of a BookingService. If you want to use several service provider, you have to stop the actual service and install the new one.
• karaf-jpa-example-features provides a Karaf features repository used for the deployment.

Build

The build uses Apache Maven. Simply use:

mvn clean install

Feature and Deployment

On a running Karaf instance, register the features repository using:

karaf@root()> feature:repo-add mvn:org.apache.karaf.examples/karaf-jpa-example-features/LATEST/xml

Then, you can install the datasource feature:

karaf@root()> feature:install karaf-jpa-example-datasource

Then, you can install the service command feature (commands booking:xxx will not be available until you have installed a provider):

karaf@root()> feature:install karaf-jpa-example-command

And install the service provider you want to use (for example EclipseLink using declarative service):

karaf@root()> feature:install karaf-jpa-example-provider-ds-eclipselink

Usage

Once you have installed the feature, you can see new commands available in the Apache Karaf shell.

booking:add command adds a new booking in the booking service. For instance:

karaf@root()> booking:add Doe AF520

booking:list command lists the current bookings:

karaf@root()> booking:list
ID      │ Flight │ Customer
────────┼────────┼─────────
1       │ AF520  │ Doe

booking:get command get the booking with id:

karaf@root()> booking:get 1
ID      │ Flight │ Customer
────────┼────────┼─────────
1       │ AF520  │ Doe

booking:remove command removes a booking from the booking service:

karaf@root()> booking:remove 1