org.apache.wicket.request.cycle.PageRequestHandlerTracker.java Source code

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Here is the source code for org.apache.wicket.request.cycle.PageRequestHandlerTracker.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.wicket.request.cycle;

import org.apache.wicket.MetaDataKey;
import org.apache.wicket.core.request.handler.IPageRequestHandler;
import org.apache.wicket.request.IRequestHandler;
import org.apache.wicket.request.IRequestHandlerDelegate;

/**
 * Registers and retrieves first and last executed {@link IPageRequestHandler} in a request cycle.
 * Can be used to find out what is the requested page and what is the actual response page.
 * <p>
 * To use it an application needs to register it with:
 *     <pre><code>
 *          application.getRequestCycleListeners().add(new PageRequestHandlerTracker());
 *     </code></pre>
 * <p>
 * The result can then be accessed at the end of each {@link RequestCycle} with:
 *     <pre><code>
 *          IPageRequestHandler first = PageRequestHandlerTracker.getFirstHandler(RequestCycle.get());
 *          IPageRequestHandler last = PageRequestHandlerTracker.getLastHandler(RequestCycle.get());
 *     </code></pre>
 *
 * @since 1.5.8
 */
public class PageRequestHandlerTracker implements IRequestCycleListener {
    /**
     * The key for the first handler
     */
    public static final MetaDataKey<IPageRequestHandler> FIRST_HANDLER_KEY = new MetaDataKey<IPageRequestHandler>() {
    };

    /**
     * The key for the last handler
     */
    public static final MetaDataKey<IPageRequestHandler> LAST_HANDLER_KEY = new MetaDataKey<IPageRequestHandler>() {
    };

    @Override
    public void onRequestHandlerResolved(RequestCycle cycle, IRequestHandler handler) {
        registerFirstHandler(cycle, handler);
        registerLastHandler(cycle, handler);
    }

    /**
     * Registers pagerequesthandler when it's resolved ,keeps up with the most recent handler resolved
     *
     * @param cycle
     *      the current request cycle
     * @param handler
     *      the request handler to register
     */
    private void registerLastHandler(RequestCycle cycle, IRequestHandler handler) {
        final IPageRequestHandler pageRequestHandler = findPageRequestHandler(handler);
        if (pageRequestHandler != null) {
            cycle.setMetaData(LAST_HANDLER_KEY, pageRequestHandler);
        }
    }

    /**
     * Registers firsthandler if it's not already registered
     *
     * @param cycle
     *      the current request cycle
     * @param handler
     *      the request handler to register
     */
    private void registerFirstHandler(RequestCycle cycle, IRequestHandler handler) {
        if (getFirstHandler(cycle) == null) {
            final IPageRequestHandler pageRequestHandler = findPageRequestHandler(handler);
            if (pageRequestHandler != null) {
                cycle.setMetaData(FIRST_HANDLER_KEY, pageRequestHandler);
            }
        }
    }

    /**
     * Looking for IPageRequestHandler 
     * 
     * @param handler
     * @return IPageRequestHandler if exist otherwise null
     */
    private IPageRequestHandler findPageRequestHandler(IRequestHandler handler) {
        if (handler instanceof IPageRequestHandler) {
            return (IPageRequestHandler) handler;
        }
        if (handler instanceof IRequestHandlerDelegate) {
            return findPageRequestHandler(((IRequestHandlerDelegate) handler).getDelegateHandler());
        }
        return null;
    }

    /**
    * retrieves last handler from request cycle
    *
    * @param cycle
    * @return last handler
    */
    public static IPageRequestHandler getLastHandler(RequestCycle cycle) {
        return cycle.getMetaData(LAST_HANDLER_KEY);
    }

    /**
     * retrieves first handler from the request cycle
     *
     * @param cycle
     * @return first handler
     */
    public static IPageRequestHandler getFirstHandler(RequestCycle cycle) {
        return cycle.getMetaData(FIRST_HANDLER_KEY);
    }
}