    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
    015    package 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.ioc.services.TypeCoercer
    023     * @see org.apache.tapestry5.ValueEncoder
    024     */
    025    public 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    }