001package org.apache.turbine.modules.screens;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 *
012 *   http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022
023// Turbine stuff.
024
025import org.apache.turbine.modules.Screen;
026import org.apache.turbine.pipeline.PipelineData;
027import org.apache.turbine.util.RunData;
028
029/**
030 * Base class for writing Screens that output binary data.  This class
031 * is provided as a helper class for those who want to write Screens
032 * that output raw binary data.  For example, it may be extended into
033 * a Screen that outputs a SVG file or a SWF (Flash Player format)
034 * movie.  The only thing one has to do is to implement the two
035 * methods <code>getContentType(PipelineData data)</code> and
036 * <code>doOutput(PipelineData data)</code> (see below).
037 *
038 * <p> You might want to take a look at the ImageServer screen class
039 * contained in the TDK.<br>
040 *
041 * @author <a href="mailto:rkoenig@chez.com">Regis Koenig</a>
042 * @author <a href="mailto:peter@courcoux.biz">Peter Courcoux</a>
043 * @version $Id: RawScreen.java 1854797 2019-03-04 20:41:39Z tv $
044 */
045public abstract class RawScreen implements Screen
046{
047    /**
048     * Build the Screen.  This method actually makes a call to the
049     * doOutput() method in order to generate the Screen content.
050     *
051     * @param pipelineData Turbine information.
052     * @return A ConcreteElement.
053     * @throws Exception a generic exception.
054     */
055    @Override
056    public final String doBuild(PipelineData pipelineData)
057            throws Exception
058    {
059        RunData data = pipelineData.getRunData();
060        data.getResponse().setContentType(getContentType(pipelineData));
061        data.declareDirectResponse();
062        doOutput(pipelineData);
063        return null;
064    }
065
066    /**
067     * Set the content type.  This method should be overridden to
068     * actually set the real content-type header of the output.
069     *
070     * @param pipelineData Turbine information.
071     * @return A String with the content type.
072     */
073    protected abstract String getContentType(PipelineData pipelineData);
074
075    /**
076     * Actually output the dynamic content.  The OutputStream can be
077     * accessed like this: <pre>OutputStream out =
078     * data.getResponse().getOutputStream();</pre>.
079     *
080     * @param pipelineData Turbine information.
081     * @throws Exception a generic exception.
082     */
083    protected abstract void doOutput(PipelineData pipelineData) throws Exception;
084
085    /**
086     * The layout must be set to null.
087     *
088     * @param pipelineData Turbine information.
089     * @return A null String.
090     */
091    @Override
092    public final String getLayout(PipelineData pipelineData)
093    {
094        return null;
095    }
096}