    001//
    002// Copyright 2011 The Apache Software Foundation
    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.transform;
    016
    017import org.apache.tapestry5.ioc.Invokable;
    018import org.apache.tapestry5.ioc.OperationTracker;
    019import org.apache.tapestry5.runtime.ComponentEvent;
    020
    021/**
    022 * Used  to encapsulate the list of {@link EventHandlerMethodParameterProvider}s for a particular
    023 * method of a particular component, providing {@link OperationTracker} behavior as parameter values
    024 * are obtained/computed/coerced.
    025 *
    026 * @since 5.3
    027 */
    028public class EventHandlerMethodParameterSource
    029{
    030    private static final class ParameterExtractor implements Invokable<Object> {
    031        private final EventHandlerMethodParameterProvider[] providers;
    032        private final int index;
    033        private final ComponentEvent event;
    034
    035        private ParameterExtractor(EventHandlerMethodParameterProvider[] providers, int index, ComponentEvent event) {
    036            this.providers = providers;
    037            this.index = index;
    038            this.event = event;
    039        }
    040
    041        public Object invoke()
    042        {
    043            return providers[index].valueForEventHandlerMethodParameter(event);
    044        }
    045    }
    046
    047    private final String methodIdentifier;
    048
    049    private final OperationTracker operationTracker;
    050
    051    private final EventHandlerMethodParameterProvider[] providers;
    052
    053    public EventHandlerMethodParameterSource(String methodIdentifier, OperationTracker operationTracker, EventHandlerMethodParameterProvider[] providers)
    054    {
    055
    056        this.methodIdentifier = methodIdentifier;
    057        this.operationTracker = operationTracker;
    058        this.providers = providers;
    059    }
    060
    061    public Object get(final ComponentEvent event, final int index)
    062    {
    063        // Hopefully this will not be too much overhead; it's really nice to be able to track what parameter
    064        // caused a failure.
    065
    066        return operationTracker.invoke("Obtaining value for parameter #" + (index + 1) + " of "+ methodIdentifier,
    067                new ParameterExtractor(providers, index, event));
    068    }
    069}