| /** |
| * |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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.xbean.recipe; |
| |
| /** |
| * Reference is a named (lazy) reference from one object to another. This data class is updated when the reference |
| * is resolved which can be immedately when the ref is created, or later when an instance with the referenced |
| * name is created. |
| * <p/> |
| * When the reference is resolved, an optional Action will be invoked which is commonly used to update a |
| * property on the source object of the reference. |
| */ |
| public class Reference { |
| private final String name; |
| private boolean resolved; |
| private Object instance; |
| private Action action; |
| |
| /** |
| * Create a reference to the specified name. |
| * @param name the name of the referenced object |
| */ |
| public Reference(String name) { |
| this.name = name; |
| } |
| |
| /** |
| * Gets the name of the referenced object. |
| * @return name the name of the referenced object |
| */ |
| public String getName() { |
| return name; |
| } |
| |
| /** |
| * Has this reference been resolved? |
| * @return true if the reference has been resolved; false otherwise |
| */ |
| public boolean isResolved() { |
| return resolved; |
| } |
| |
| /** |
| * Gets the referenced object instance or null if the reference has not been resolved yet; |
| * |
| * @return the referenced object instance or null |
| */ |
| public Object get() { |
| return instance; |
| } |
| |
| /** |
| * Sets the referenced object instance. If an action is registered the onSet method is invoked. |
| * |
| * @param object the reference instance |
| */ |
| public void set(Object object) { |
| if (resolved) { |
| throw new ConstructionException("Reference has already been resolved"); |
| } |
| resolved = true; |
| this.instance = object; |
| if (action != null) { |
| action.onSet(this); |
| } |
| } |
| |
| /** |
| * Registers an action to invoke when the instance is set. If the instance, has already been set, the |
| * onSet method will immedately be invoked. |
| * |
| * @return the action to invoke when this refernce is resolved; not null |
| */ |
| public void setAction(Action action) { |
| if (action == null) { |
| throw new NullPointerException("action is null"); |
| } |
| this.action = action; |
| if (resolved) { |
| action.onSet(this); |
| } |
| } |
| |
| public static interface Action { |
| void onSet(Reference ref); |
| } |
| } |