// Copyright 2006 The Apache Software Foundation

 //

 // Licensed under the Apache License, Version 2.0 (the "License");

 // you may not use this file except in compliance with the License.

 // You may obtain a copy of the License at

 //

 //     http://www.apache.org/licenses/LICENSE-2.0

 //

 // Unless required by applicable law or agreed to in writing, software

 // distributed under the License is distributed on an "AS IS" BASIS,

 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 // See the License for the specific language governing permissions and

 // limitations under the License.

 package org.apache.tapestry5.internal.bindings;

 import org.apache.tapestry5.Binding;

 import org.apache.tapestry5.ioc.BaseLocatable;

 import org.apache.tapestry5.ioc.Location;

 import org.apache.tapestry5.ioc.internal.util.TapestryException;

 import java.lang.annotation.Annotation;

 /**

  * Abstract base class for bindings. Assumes that the binding is read only and invariant. Subclasses must provide an

  * implementation of {@link Binding#get()}.

  */

 public abstract class AbstractBinding extends BaseLocatable implements Binding

 {

     public AbstractBinding()

     {

         this(null);

     }

     protected AbstractBinding(Location location)

     {

         super(location);

     }

     /**

      * @throws TapestryException always

      */

     public void set(Object value)

     {

         throw new TapestryException(BindingsMessages.bindingIsReadOnly(this), this, null);

     }

     /**

      * Returns true. Subclasses that do not supply a fixed, read-only value should override this method to return

      * false.

      */

     public boolean isInvariant()

     {

         return true;

     }

     /**

      * Returns the actual class, by invoking {@link Binding#get()}. Subclasses may override this method to work more

      * efficiently (say, when the binding type is known statically).

      */

     public Class getBindingType()

     {

         return get().getClass();

     }

     /**

      * Always returns null. Bindings that provide access to a method or field will override this method to return the

      * appropriate annotation.

      */

     public <T extends Annotation> T getAnnotation(Class<T> annotationClass)

     {

         return null;

     }

 }