001    /*****************************************************************************
002     * Copyright (C) PicoContainer Organization. All rights reserved.            *
003     * ------------------------------------------------------------------------- *
004     * The software in this package is published under the terms of the BSD      *
005     * style license a copy of which has been included with this distribution in *
006     * the LICENSE.txt file.                                                     *
007     *                                                                           *
008     * Original code by                                                          *
009     *****************************************************************************/
010    package org.picocontainer.gems.adapters;
011    
012    import com.thoughtworks.proxy.ProxyFactory;
013    import com.thoughtworks.proxy.factory.StandardProxyFactory;
014    import com.thoughtworks.proxy.kit.ObjectReference;
015    import com.thoughtworks.proxy.kit.ReflectionUtils;
016    import com.thoughtworks.proxy.toys.delegate.Delegating;
017    import com.thoughtworks.proxy.toys.hotswap.HotSwapping;
018    
019    import org.picocontainer.ComponentAdapter;
020    import org.picocontainer.PicoContainer;
021    import org.picocontainer.defaults.DecoratingComponentAdapter;
022    
023    import java.util.Arrays;
024    import java.util.HashSet;
025    import java.util.Set;
026    
027    
028    /**
029     * This component adapter makes it possible to hide the implementation of a real subject (behind a proxy). If the key of the
030     * component is of type {@link Class} and that class represents an interface, the proxy will only implement the interface
031     * represented by that Class. Otherwise (if the key is something else), the proxy will implement all the interfaces of the
032     * underlying subject. In any case, the proxy will also implement {@link com.thoughtworks.proxy.toys.hotswap.Swappable}, making
033     * it possible to swap out the underlying subject at runtime. <p/> <em>
034     * Note that this class doesn't cache instances. If you want caching,
035     * use a {@link org.picocontainer.defaults.CachingComponentAdapter} around this one.
036     * </em>
037     * 
038     * @author Paul Hammant
039     * @author Aslak Helles&oslash;y
040     * @version $Revision: 2631 $
041     */
042    public class HotSwappingComponentAdapter extends DecoratingComponentAdapter {
043        private final ProxyFactory proxyFactory;
044    
045        private static class ImplementationHidingReference implements ObjectReference {
046            private final ComponentAdapter delegate;
047            private Object componentInstance;
048            private final PicoContainer container;
049    
050            public ImplementationHidingReference(ComponentAdapter delegate, PicoContainer container) {
051                this.delegate = delegate;
052                this.container = container;
053            }
054    
055            public Object get() {
056                if (componentInstance == null) {
057                    componentInstance = delegate.getComponentInstance(container);
058                }
059                return componentInstance;
060            }
061    
062            public void set(Object item) {
063                componentInstance = item;
064            }
065        }
066    
067        public HotSwappingComponentAdapter(final ComponentAdapter delegate, ProxyFactory proxyFactory) {
068            super(delegate);
069            this.proxyFactory = proxyFactory;
070        }
071    
072        public HotSwappingComponentAdapter(ComponentAdapter delegate) {
073            this(delegate, new StandardProxyFactory());
074        }
075    
076        public Object getComponentInstance(final PicoContainer container) {
077            final Class[] proxyTypes;
078            if (getComponentKey() instanceof Class && proxyFactory.canProxy((Class)getComponentKey())) {
079                proxyTypes = new Class[]{(Class)getComponentKey()};
080            } else {
081                Set types = new HashSet(Arrays.asList(getComponentImplementation().getInterfaces()));
082                ReflectionUtils.addIfClassProxyingSupportedAndNotObject(getComponentImplementation(), types, proxyFactory);
083                proxyTypes = (Class[])types.toArray(new Class[types.size()]);
084            }
085            ObjectReference reference = new ImplementationHidingReference(getDelegate(), container);
086            return HotSwapping.object(proxyTypes, proxyFactory, reference, Delegating.MODE_DIRECT);
087        }
088    }