| /* |
| * 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.commons.proxy.provider; |
| |
| import org.apache.commons.proxy.ObjectProvider; |
| |
| import java.io.Serializable; |
| |
| /** |
| * Wraps another object provider, making sure to only call it once, returning the value returned from the wrapped |
| * provider on all subsequent invocations. |
| * |
| * @author James Carman |
| * @since 1.0 |
| */ |
| public class SingletonProvider extends ProviderDecorator implements Serializable |
| { |
| //********************************************************************************************************************** |
| // Fields |
| //********************************************************************************************************************** |
| |
| private transient Object instance; |
| |
| //********************************************************************************************************************** |
| // Constructors |
| //********************************************************************************************************************** |
| |
| public SingletonProvider( ObjectProvider inner ) |
| { |
| super(inner); |
| } |
| |
| //********************************************************************************************************************** |
| // ObjectProvider Implementation |
| //********************************************************************************************************************** |
| |
| public Object getObject() |
| { |
| synchronized( this ) |
| { |
| if( instance == null ) |
| { |
| instance = super.getObject(); |
| } |
| } |
| return instance; |
| } |
| } |
| |