CDO Model Repository Documentation > Programmer's Guide > Developing Client Applications

View Providers


Author: Victor Roldan Betancort

A view provider allows clients to inject custom logic into the resource factory mechansim, capable of handling the whole session and view instantiation process. This permits to obtain resources through the resource set API transparently, without any prior CDO client API code. The view provider automatically kicks in the middle of the ResourceSet.getResource() call, forgetting about the whole openning session / openning transaction process, which happens behind the scenes.

This is quite useful when integrating CDO with EMF-based frameworks and tools that are not prepared for a CDO scenario themselves.

Table of Contents

Implementing a View Provider
Contributing View Providers Programmatically
Contributing View Providers Using Extension Points

1  Implementing a View Provider

Clients should implement the CDOViewProvider interface, or sub class the AbstractCDOViewProvider class, which provides common functionality.

The example below shows a simple implementation that opens a new session to a local server and a new transaction on that session.  
 new AbstractCDOViewProvider("cdo\\.local:.*"100)
  private IManagedContainer container;

   public CDOView getView(URI uri, ResourceSet resourceSet)
    if (container == null)
      container = new ManagedContainer();

    int startIndex = uri.toString().indexOf(':');
    String repoName = uri.toString().substring(startIndex);

    IConnector connector = (IConnector)container.getElement("org.eclipse.net4j.connectors""tcp""localhost");

    CDONet4jSessionConfiguration config = CDONet4jUtil.createNet4jSessionConfiguration();

    CDOSession session = config.openNet4jSession();
    return session.openTransaction();

 The example provider catches all URIs with shape "cdo.local:".
 Register the provider with CDOViewProviderRegistry.

2  Contributing View Providers Programmatically

A client's view provider implementation can be contributed programmatically to the CDOViewProviderRegistry, as the following example suggests:  
// Instantiate your view provider
CDOViewProvider viewProvider =  org.eclipse.emf.internal.cdo.view.PluginContainerViewProvider.INSTANCE;

// Add the instance to the registry

 Get the target CDOViewProvider implementation.
 Add the provider instance to CDOViewProviderRegistry.

3  Contributing View Providers Using Extension Points

A specific CDOViewProvider implementation can also be contributed using the org.eclipse.emf.cdo.viewProviders extension point. Clients specify:


Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.