org.apache.wicket.markup.transformer.AbstractTransformerBehavior.java Source code

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Here is the source code for org.apache.wicket.markup.transformer.AbstractTransformerBehavior.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.markup.transformer;

import org.apache.wicket.Component;
import org.apache.wicket.Page;
import org.apache.wicket.WicketRuntimeException;
import org.apache.wicket.behavior.Behavior;
import org.apache.wicket.protocol.http.BufferedWebResponse;
import org.apache.wicket.request.Response;
import org.apache.wicket.request.cycle.RequestCycle;
import org.apache.wicket.request.http.WebResponse;

/**
 * A {@link Behavior} which can be added to any component. It allows to post-process (transform) the
 * markup generated by the component.
 * 
 * @see org.apache.wicket.markup.transformer.AbstractOutputTransformerContainer
 * 
 * @author Juergen Donnerstag
 */
public abstract class AbstractTransformerBehavior extends Behavior implements ITransformer {
    private static final long serialVersionUID = 1L;

    /**
     * The request cycle's response before the transformation.
     */
    private transient Response originalResponse;

    /**
     * Create a new response object which is used to store the markup generated by the child
     * objects.
     * 
     * @param originalResponse
     *            the original web response or {@code null} if it isn't a {@link WebResponse}
     * 
     * @return Response object. Must not be null
     */
    protected BufferedWebResponse newResponse(final WebResponse originalResponse) {
        return new BufferedWebResponse(originalResponse);
    }

    @Override
    public void beforeRender(Component component) {
        super.beforeRender(component);

        final RequestCycle requestCycle = RequestCycle.get();

        // Temporarily replace the web response with a String response
        originalResponse = requestCycle.getResponse();

        WebResponse origResponse = (WebResponse) ((originalResponse instanceof WebResponse) ? originalResponse
                : null);
        BufferedWebResponse tempResponse = newResponse(origResponse);

        // temporarily set StringResponse to collect the transformed output
        requestCycle.setResponse(tempResponse);
    }

    @Override
    public void afterRender(final Component component) {
        final RequestCycle requestCycle = RequestCycle.get();

        try {
            BufferedWebResponse tempResponse = (BufferedWebResponse) requestCycle.getResponse();

            if (component instanceof Page && originalResponse instanceof WebResponse) {
                tempResponse.writeMetaData((WebResponse) originalResponse);
            }

            // Transform the data
            CharSequence output = transform(component, tempResponse.getText());
            originalResponse.write(output);
        } catch (Exception ex) {
            throw new WicketRuntimeException("Error while transforming the output of component: " + component, ex);
        } finally {
            // Restore the original response object
            requestCycle.setResponse(originalResponse);
        }
    }

    @Override
    public void detach(Component component) {
        originalResponse = null;
        super.detach(component);
    }

    @Override
    public abstract CharSequence transform(final Component component, final CharSequence output) throws Exception;
}