001// Copyright 2006, 2011 The Apache Software Foundation 002// 003// Licensed under the Apache License, Version 2.0 (the "License"); 004// you may not use this file except in compliance with the License. 005// You may obtain a copy of the License at 006// 007// http://www.apache.org/licenses/LICENSE-2.0 008// 009// Unless required by applicable law or agreed to in writing, software 010// distributed under the License is distributed on an "AS IS" BASIS, 011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 012// See the License for the specific language governing permissions and 013// limitations under the License. 014 015package org.apache.tapestry5.internal.bindings; 016 017import org.apache.tapestry5.Binding; 018import org.apache.tapestry5.ioc.BaseLocatable; 019import org.apache.tapestry5.ioc.Location; 020import org.apache.tapestry5.ioc.internal.util.TapestryException; 021 022import java.lang.annotation.Annotation; 023 024/** 025 * Abstract base class for bindings. Assumes that the binding is read only and invariant. Subclasses must provide an 026 * implementation of {@link Binding#get()}. 027 */ 028public abstract class AbstractBinding extends BaseLocatable implements Binding 029{ 030 public AbstractBinding() 031 { 032 this(null); 033 } 034 035 protected AbstractBinding(Location location) 036 { 037 super(location); 038 } 039 040 /** 041 * @throws TapestryException always 042 */ 043 public void set(Object value) 044 { 045 throw new TapestryException(String.format("Binding %s is read-only.", this), this, null); 046 } 047 048 /** 049 * Returns true. Subclasses that do not supply a fixed, read-only value should override this method to return 050 * false. 051 */ 052 public boolean isInvariant() 053 { 054 return true; 055 } 056 057 /** 058 * Returns the actual class, by invoking {@link Binding#get()}. Subclasses may override this method to work more 059 * efficiently (say, when the binding type is known statically). 060 */ 061 public Class getBindingType() 062 { 063 return get().getClass(); 064 } 065 066 /** 067 * Always returns null. Bindings that provide access to a method or field will override this method to return the 068 * appropriate annotation. 069 */ 070 public <T extends Annotation> T getAnnotation(Class<T> annotationClass) 071 { 072 return null; 073 } 074 075}