    001    // Copyright 2006, 2007, 2008, 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
    015    package org.apache.tapestry5.internal.services;
    016
    017    import org.apache.tapestry5.func.F;
    018    import org.apache.tapestry5.func.Mapper;
    019    import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
    020    import org.apache.tapestry5.ioc.internal.util.OneShotLock;
    021    import org.apache.tapestry5.ioc.services.ThreadCleanupListener;
    022    import org.apache.tapestry5.ioc.util.AvailableValues;
    023    import org.apache.tapestry5.ioc.util.Stack;
    024    import org.apache.tapestry5.ioc.util.UnknownValueException;
    025    import org.apache.tapestry5.services.Environment;
    026
    027    import java.util.LinkedList;
    028    import java.util.List;
    029    import java.util.Map;
    030
    031    /**
    032     * A non-threadsafe implementation (expects to use the "perthread" service lifecyle).
    033     */
    034    public class EnvironmentImpl implements Environment, ThreadCleanupListener
    035    {
    036
    037        // My generics mojo breaks down when we talk about the key and the value being related
    038        // types.
    039
    040        private Map<Class, LinkedList> typeToStack = CollectionFactory.newMap();
    041
    042        // Support for cloak/decloak.  Cloaking pushes the current typeToStack map onto the stack
    043        // and creates a new, empyt, Map to replace it. Decloaking discards the current map
    044        // and replaces it with the top map on the stack.
    045
    046        private final Stack<Map<Class, LinkedList>> cloakStack = CollectionFactory.newStack();
    047
    048        private final OneShotLock lock = new OneShotLock();
    049
    050        @SuppressWarnings("unchecked")
    051        private <T> LinkedList<T> stackFor(Class<T> type)
    052        {
    053            lock.check();
    054
    055            LinkedList<T> result = typeToStack.get(type);
    056
    057            if (result == null)
    058            {
    059                result = CollectionFactory.newLinkedList();
    060                typeToStack.put(type, result);
    061            }
    062
    063            return result;
    064        }
    065
    066        public <T> T peek(Class<T> type)
    067        {
    068            LinkedList<T> stack = stackFor(type);
    069
    070            return stack.isEmpty() ? null : stack.getFirst();
    071        }
    072
    073        public <T> T peekRequired(Class<T> type)
    074        {
    075            T result = peek(type);
    076
    077            if (result == null)
    078            {
    079                List<Class> types = CollectionFactory.newList();
    080                for (Map.Entry<Class, LinkedList> e : typeToStack.entrySet())
    081                {
    082                    LinkedList list = e.getValue();
    083
    084                    if (list != null && !list.isEmpty())
    085                        types.add(e.getKey());
    086                }
    087
    088                throw new UnknownValueException(String.format("No object of type %s is available from the Environment.", type.getName()),
    089                        new AvailableValues("Environmentals",
    090                                F.flow(typeToStack.keySet()).map(new Mapper<Class, String>()
    091                                {
    092                                    public String map(Class element)
    093                                    {
    094                                        return element.getName();
    095                                    }
    096                                }).toList()));
    097            }
    098
    099            return result;
    100        }
    101
    102        public <T> T pop(Class<T> type)
    103        {
    104            LinkedList<T> stack = stackFor(type);
    105
    106            return stack.removeFirst();
    107        }
    108
    109        public <T> T push(Class<T> type, T instance)
    110        {
    111            LinkedList<T> stack = stackFor(type);
    112
    113            T result = stack.isEmpty() ? null : stack.getFirst();
    114
    115            stack.addFirst(instance);
    116
    117            return result;
    118        }
    119
    120        public void clear()
    121        {
    122            throw new IllegalStateException("Environment.clear() is no longer supported.");
    123        }
    124
    125        public void threadDidCleanup()
    126        {
    127            lock.lock();
    128        }
    129
    130        public void cloak()
    131        {
    132            cloakStack.push(typeToStack);
    133
    134            typeToStack = CollectionFactory.newMap();
    135        }
    136
    137        public void decloak()
    138        {
    139            typeToStack = cloakStack.pop();
    140        }
    141    }