001// Copyright 2004, 2005 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.hivemind.lib.impl;
016
017import java.util.Collections;
018import java.util.HashMap;
019import java.util.Map;
020
021import org.apache.hivemind.ApplicationRuntimeException;
022import org.apache.hivemind.impl.BaseLocatable;
023import org.apache.hivemind.lib.DefaultImplementationBuilder;
024import org.apache.hivemind.service.ClassFab;
025import org.apache.hivemind.service.ClassFabUtils;
026import org.apache.hivemind.service.ClassFactory;
027import org.apache.hivemind.service.MethodIterator;
028
029/**
030 * Implemenation of {@link org.apache.hivemind.lib.DefaultImplementationBuilder}.
031 * 
032 * @author Howard Lewis Ship
033 */
034public class DefaultImplementationBuilderImpl extends BaseLocatable implements
035        DefaultImplementationBuilder
036{
037    private Map _instances = Collections.synchronizedMap(new HashMap());
038
039    private ClassFactory _classFactory;
040
041    public Object buildDefaultImplementation(Class interfaceType)
042    {
043        Object result = _instances.get(interfaceType);
044
045        if (result == null)
046        {
047            result = create(interfaceType);
048
049            _instances.put(interfaceType, result);
050        }
051
052        return result;
053    }
054
055    private Object create(Class interfaceType)
056    {
057        Class defaultClass = createClass(interfaceType);
058
059        try
060        {
061            return defaultClass.newInstance();
062        }
063        catch (Exception ex)
064        {
065            throw new ApplicationRuntimeException(ImplMessages.unableToCreateDefaultImplementation(
066                    interfaceType,
067                    ex), ex);
068        }
069    }
070
071    private Class createClass(Class interfaceType)
072    {
073        if (!interfaceType.isInterface())
074            throw new ApplicationRuntimeException(ImplMessages.notAnInterface(interfaceType));
075
076        String name = ClassFabUtils.generateClassName(interfaceType);
077
078        ClassFab cf = _classFactory.newClass(name, Object.class);
079
080        cf.addInterface(interfaceType);
081
082        MethodIterator mi = new MethodIterator(interfaceType);
083
084        while (mi.hasNext())
085        {
086            ClassFabUtils.addNoOpMethod(cf, mi.next());
087        }
088
089        if (!mi.getToString())
090            ClassFabUtils.addToStringMethod(cf, ImplMessages
091                    .defaultImplementationDescription(interfaceType));
092
093        return cf.createClass();
094    }
095
096    public void setClassFactory(ClassFactory factory)
097    {
098        _classFactory = factory;
099    }
100
101}