001// Copyright 2008, 2010 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;
016
017import java.io.Serializable;
018import java.util.Optional;
019
020import org.apache.tapestry5.EventContext;
021import org.apache.tapestry5.commons.util.CommonsUtils;
022
023/**
024 * Placeholder used when no context is available.
025 */
026public class EmptyEventContext implements EventContext, Serializable
027{
028    private static final long serialVersionUID = 1L;
029
030    /**
031     * Always returns zero.
032     */
033    public int getCount()
034    {
035        return 0;
036    }
037
038    /**
039     * This should never be called because the count is always zero.
040     */
041    public <T> T get(Class<T> desiredType, int index)
042    {
043        return null;
044    }
045
046    public String[] toStrings()
047    {
048        return CommonsUtils.EMPTY_STRING_ARRAY;
049    }
050
051    @Override
052    public boolean isEmpty()
053    {
054        return true;
055    }
056
057    @Override
058    public <T> Optional<T> tryGet(Class<T> desiredType, int index)
059    {
060        return Optional.empty();
061    }
062}