    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;
    016
    017/**
    018 * A collection of parameters that may eventually be passed to an event handler method. Includes the
    019 * ability to coerce
    020 * or encode parameters as needed.
    021 *
    022 * @see org.apache.tapestry5.commons.services.TypeCoercer
    023 * @see org.apache.tapestry5.ValueEncoder
    024 */
    025public interface EventContext
    026{
    027    /**
    028     * Returns the number of parameter values that can be extracted.
    029     */
    030    int getCount();
    031
    032    /**
    033     * Extracts a parameter value and coerces or decodes it to the desired type.
    034     *
    035     * @param desiredType
    036     *            the type of value required
    037     * @param index
    038     *            identifies which parameter value to extract
    039     * @return the value extracted and converted or coerced
    040     * @throws RuntimeException
    041     *             if the value can't be converted or the index is out of range
    042     */
    043    <T> T get(Class<T> desiredType, int index);
    044
    045    /**
    046     * Extracts the value of each context value as a string.
    047     *
    048     * @return context values
    049     * @since 5.2.0
    050     */
    051    String[] toStrings();
    052}