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