001// Copyright 2006-2014 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.internal.services;
016
017import org.apache.tapestry5.func.F;
018import org.apache.tapestry5.func.Mapper;
019import org.apache.tapestry5.func.Predicate;
020import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
021import org.apache.tapestry5.ioc.internal.util.OneShotLock;
022import org.apache.tapestry5.ioc.util.AvailableValues;
023import org.apache.tapestry5.ioc.util.UnknownValueException;
024import org.apache.tapestry5.services.Environment;
025
026import java.util.LinkedList;
027import java.util.List;
028import java.util.Map;
029import java.util.Map.Entry;
030
031/**
032 * A non-threadsafe implementation (expects to use the "perthread" service lifecyle).
033 */
034public class EnvironmentImpl implements Environment
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    private final OneShotLock lock = new OneShotLock();
043
044    @SuppressWarnings("unchecked")
045    private <T> LinkedList<T> stackFor(Class<T> type)
046    {
047        lock.check();
048
049        LinkedList<T> result = typeToStack.get(type);
050
051        if (result == null)
052        {
053            result = CollectionFactory.newLinkedList();
054            typeToStack.put(type, result);
055        }
056
057        return result;
058    }
059
060    public <T> T peek(Class<T> type)
061    {
062        LinkedList<T> stack = stackFor(type);
063
064        return stack.isEmpty() ? null : stack.getFirst();
065    }
066
067    public <T> T peekRequired(Class<T> type)
068    {
069        T result = peek(type);
070
071        if (result == null)
072        {
073            List<Class> types = CollectionFactory.newList();
074            for (Map.Entry<Class, LinkedList> e : typeToStack.entrySet())
075            {
076                LinkedList list = e.getValue();
077
078                if (list != null && !list.isEmpty())
079                    types.add(e.getKey());
080            }
081
082            throw new UnknownValueException(String.format("No object of type %s is available from the Environment.", type.getName()),
083                    new AvailableValues("Environmentals",
084                            F.flow(typeToStack.entrySet()).remove(new Predicate<Entry<Class, LinkedList>>()
085                            {
086                                public boolean accept(Entry<Class, LinkedList> element)
087                                {
088                                    return element.getValue().isEmpty();
089                                }
090                            }).map(new Mapper<Entry<Class, LinkedList>, String>()
091                            {
092                                public String map(Entry<Class, LinkedList> element)
093                                {
094                                    return element.getKey().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 threadDidCleanup()
121    {
122        lock.lock();
123    }
124
125    public void cloak()
126    {
127        throw new UnsupportedOperationException("cloak() is no longer available in Tapestry 5.4.");
128    }
129
130    public void decloak()
131    {
132        throw new UnsupportedOperationException("decloak() is no longer available in Tapestry 5.4.");
133    }
134}