Registering services to the repository in kettle

Introduction

One of the changes in version 4 of Pentaho Data Integration is the introduction of concept of service for repositories. To support this concept the repository API of PDI has changed a little bit. This document describes how you can creates these repository services and register them to repository.

Changes to Repository API

To enable the registering of these repository services, we have added some new methods to the repository API. Details on these method are described below

/**
  * Retrieves the current list of of IRepository Services.
  *
  * @return List of repository services
  * @throws KettleException in case something goes horribly wrong.
  */
  public List<Class<? extends IRepositoryService>> getServiceInterfaces() throws KettleException;

  /**
  * Retrieves a given repository service
  * @param  service class name
  * @return repository service
  *
  * @throws KettleException in case something goes horribly wrong.
  */
  public IRepositoryService getService(Class<? extends IRepositoryService> clazz) throws KettleException;

  /**
   * Checks whether a given repository service is available or not
   *
   * @param repository service class that needs to be checked for support
   * @throws KettleException in case something goes horribly wrong.
   */
  public boolean hasService(Class<? extends IRepositoryService> clazz) throws KettleException;

Registering services to repository

To add a new service to repository, create an interface for the service and provide an implementation. This new service needs to extend IRepositoryService. This is a marker interface which identifies this new service as a repository service. Once the service is defined, it needs to register itself in the repository implementation. In future we can have this registration done using spring which will even more pluggable.

Adding service in detail

To explain this we will use an example of a repository service that provided management of access control list for the repository objects. We created an interface for this service which is described below

public interface IAclManager extends IRepositoryService{
  /**
   * Get the Permissions of a repository object.
   *
   * @param Object Id of the repository object
   * @param forceParentInheriting retrieve the effective ACLs as if 'inherit from parent' were true
   *
   * @return The permissions.
   * @throws KettleException in case something goes horribly wrong
   */
  public ObjectAcl getAcl(ObjectId id, boolean forceParentInheriting) throws KettleException;

  /**
   * Set the Permissions of a repository element.
   *
   * @param Acl object that needs to be set.
   * @param Object Id of a file for which the acl are being set.
   *
   * @throws KettleException in case something goes horribly wrong
   */
  public  void setAcl(ObjectId id, ObjectAcl aclObject) throws KettleException;

}

One item to note in this interface that it extends IRepositoryService. This is a marker interface which identifies this service to be a repository service. In a repository's implementation we instantiated the service implementation and register this service with repository.      IAclManager aclImpl  = new AclManagerImpl();
      registerRepositoryService(IAclManager.class, aclImpl);            
ResigerRepositoryService is a convenience method, all this is doing is adding the service interface and its implementation in a map. Once the services are registered you can the retrieve this service by calling getService method in the Repository API

If this new service need a UI Support,  you can extend AbstractRepositoryExplorerUISupport class and implement the setup method

@Override
  protected void setup() {
    overlays.add(new DefaultXulOverlay(
    "org/pentaho/di/ui/repository/repositoryexplorer/xul/acl-enabled-layout-overlay.xul")); //$NON-NLS-1$
    PermissionsController permissionsController = new PermissionsController();
    controllerNames.add(permissionsController.getName());
    handlers.add(permissionsController);
  }

You need to add any overlays and event handlers this service will have. Finally we need register UI Support class.

UISupportRegistery.getInstance().registerUISupport(IAclManager.class, AclUISupport.class);

These UI Support objects are currently getting consumed in the repository explorer. We need to extend these UISupport object to be applicable to the whole spoon UI.