    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}