001// Copyright 2009, 2010, 2011 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.tapestry5.ioc.internal.services;
016
017import java.lang.reflect.Method;
018
019import org.apache.tapestry5.ioc.Invocation;
020import org.apache.tapestry5.ioc.MethodAdvice;
021import org.apache.tapestry5.ioc.MethodAdviceReceiver;
022import org.apache.tapestry5.ioc.ObjectCreator;
023import org.apache.tapestry5.ioc.annotations.NotLazy;
024import org.apache.tapestry5.ioc.annotations.PreventServiceDecoration;
025import org.apache.tapestry5.ioc.internal.util.InternalUtils;
026import org.apache.tapestry5.ioc.services.LazyAdvisor;
027import org.apache.tapestry5.ioc.services.ThunkCreator;
028
029@PreventServiceDecoration
030public class LazyAdvisorImpl implements LazyAdvisor
031{
032    private final ThunkCreator thunkCreator;
033
034    public LazyAdvisorImpl(ThunkCreator thunkCreator)
035    {
036        this.thunkCreator = thunkCreator;
037    }
038
039    public void addLazyMethodInvocationAdvice(MethodAdviceReceiver methodAdviceReceiver)
040    {
041        for (Method m : methodAdviceReceiver.getInterface().getMethods())
042        {
043            if (filter(m))
044                addAdvice(m, methodAdviceReceiver);
045        }
046    }
047
048    private void addAdvice(Method method, MethodAdviceReceiver receiver)
049    {
050        final Class thunkType = method.getReturnType();
051
052        final String description = String.format("<%s Thunk for %s>", thunkType.getName(),
053                InternalUtils.asString(method));
054
055        MethodAdvice advice = new MethodAdvice()
056        {
057            /**
058             * When the method is invoked, we don't immediately proceed. Instead, we return a thunk instance
059             * that defers its behavior to the lazily invoked invocation.
060             */
061            public void advise(final Invocation invocation)
062            {
063                ObjectCreator deferred = new ObjectCreator()
064                {
065                    public Object createObject()
066                    {
067                        invocation.proceed();
068
069                        return invocation.getResult();
070                    }
071                };
072
073                ObjectCreator cachingObjectCreator = new CachingObjectCreator(deferred);
074
075                Object thunk = thunkCreator.createThunk(thunkType, cachingObjectCreator, description);
076
077                invocation.overrideResult(thunk);
078            }
079        };
080
081        receiver.adviseMethod(method, advice);
082    }
083
084    private boolean filter(Method method)
085    {
086        if (method.getAnnotation(NotLazy.class) != null)
087            return false;
088
089        if (!method.getReturnType().isInterface())
090            return false;
091
092        for (Class extype : method.getExceptionTypes())
093        {
094            if (!RuntimeException.class.isAssignableFrom(extype))
095                return false;
096        }
097
098        return true;
099    }
100}