| /* |
| * 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.bsf.util; |
| |
| import java.util.Hashtable; |
| |
| /** |
| * The <em>ObjectRegistry</em> is used to do name-to-object reference lookups. |
| * If an <em>ObjectRegistry</em> is passed as a constructor argument, then this |
| * <em>ObjectRegistry</em> will be a cascading registry: when a lookup is |
| * invoked, it will first look in its own table for a name, and if it's not |
| * there, it will cascade to the parent <em>ObjectRegistry</em>. |
| * All registration is always local. [??] |
| * |
| * @author Sanjiva Weerawarana |
| * @author Matthew J. Duftler |
| */ |
| public class ObjectRegistry { |
| Hashtable reg = new Hashtable (); |
| ObjectRegistry parent = null; |
| |
| public ObjectRegistry () { |
| } |
| public ObjectRegistry (ObjectRegistry parent) { |
| this.parent = parent; |
| } |
| // lookup an object: cascade up if needed |
| public Object lookup (String name) throws IllegalArgumentException { |
| Object obj = reg.get (name); |
| |
| if (obj == null && parent != null) { |
| obj = parent.lookup (name); |
| } |
| |
| if (obj == null) { |
| throw new IllegalArgumentException ("object '" + name + "' not in registry"); |
| } |
| |
| return obj; |
| } |
| // register an object |
| public void register (String name, Object obj) { |
| reg.put (name, obj); |
| } |
| // unregister an object (silent if unknown name) |
| public void unregister (String name) { |
| reg.remove (name); |
| } |
| } |