E4/EAS/Adapting Objects
From Eclipsepedia
The adapter pattern is widely used in the Eclipse platform as a way for different classes to retrieve information about a given object. This can usually be seen by how different views react completely different to a given object. Consider how the 'Javadoc' view renders the javadoc specification of a given class but the 'Outline' view provides an overview of the entire class instead of just the item under the current text caret.
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Eclipse 3.x API
Getting an IAdapterManager
The existing IAdapterManager can currently either be retrieved directly via a static method (Platform.getAdapterManger()) or queried through via OSGi as a service.
Adapting objects
In Eclipse 3.x, there is the org.eclipse.core.runtime.IAdaptable interface that types can implement/extend if they wish clients to adapt their object to another object.
Implementation
public interface IModelProvider { public Model getModel(); } public class ModelEditor implements IAdaptable, IModelProvider { private Model model; public Model getModel() { return model; } public Object getAdapter(Class adapter) { if (adapter == IModelProvider.class) { return this; } return null; } }
Client code
IModelProvider modelProvider = (IModelProvider) editor.getAdapter(IModelProvider.class); if (modelProvider != null) { // do something with it }
e4 (Java)
Getting an IAdapterManager
The adapter manager can be easily queried for by asking the Eclipse context.
private IAdapterManager getAdapterManager(IEclipseContext context) { return (IAdapterManager) context.get(IAdapterManager.class.getName()); }
Adapting objects
If generics could be used, the client code can be simplified as casting would no longer be required.
IAdaptable definition
public interface IAdaptable { public <T> T getAdapter(Class<T> cls); }
Implementation
public interface IModelProvider { public Model getModel(); } public class ModelEditor implements IAdaptable, IModelProvider { private Model model; public Model getModel() { return model; } public <T> T getAdapter(Class<T> adapter) { if (adapter == IModelProvider.class) { return (T) this; } return null; } }
Client code
// casting no longer required in client code IModelProvider modelProvider = editor.getAdapter(IModelProvider.class); if (modelProvider != null) { // do something with it }