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Turbine is a servlet based framework that allows experienced Java developers to quickly build secure web applications. Parts of Turbine can also be used independently of the web portion of Turbine as well. In other words, we strive to make portions of Turbine easily available for use in other applications.

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package org.apache.turbine.modules.screens;

/*
 * 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.
 */


// Turbine stuff.

import org.apache.turbine.modules.Screen;
import org.apache.turbine.pipeline.PipelineData;
import org.apache.turbine.util.RunData;

/**
 * Base class for writing Screens that output binary data.  This class
 * is provided as a helper class for those who want to write Screens
 * that output raw binary data.  For example, it may be extended into
 * a Screen that outputs a SVG file or a SWF (Flash Player format)
 * movie.  The only thing one has to do is to implement the two
 * methods getContentType(PipelineData data) and
 * doOutput(PipelineData data) (see below).
 *
 *  You might want to take a look at the ImageServer screen class
 * contained in the TDK.

 *
 * @author Regis Koenig
 * @author Peter Courcoux
 * @version $Id: RawScreen.java 1773378 2016-12-09 13:19:59Z tv $
 */
public abstract class RawScreen extends Screen
{
    /**
     * Build the Screen.  This method actually makes a call to the
     * doOutput() method in order to generate the Screen content.
     *
     * @param pipelineData Turbine information.
     * @return A ConcreteElement.
     * @throws Exception a generic exception.
     */
    @Override
    protected final String doBuild(PipelineData pipelineData)
            throws Exception
    {
        RunData data = getRunData(pipelineData);
        data.getResponse().setContentType(getContentType(pipelineData));
        data.declareDirectResponse();
        doOutput(pipelineData);
        return null;
    }

    /**
     * Set the content type.  This method should be overridden to
     * actually set the real content-type header of the output.
     *
     * @param pipelineData Turbine information.
     * @return A String with the content type.
     */
    protected abstract String getContentType(PipelineData pipelineData);

    /**
     * Actually output the dynamic content.  The OutputStream can be
     * accessed like this: 
OutputStream out =
     * data.getResponse().getOutputStream();.
     *
     * @param pipelineData Turbine information.
     * @throws Exception a generic exception.
     */
    protected abstract void doOutput(PipelineData pipelineData) throws Exception;

    /**
     * The layout must be set to null.
     *
     * @param pipelineData Turbine information.
     * @return A null String.
     */
    @Override
    public final String getLayout(PipelineData pipelineData)
    {
        return null;
    }
}