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    1   package org.apache.turbine.modules.screens;
    2
    3   /*
    4    * Licensed to the Apache Software Foundation (ASF) under one
    5    * or more contributor license agreements.  See the NOTICE file
    6    * distributed with this work for additional information
    7    * regarding copyright ownership.  The ASF licenses this file
    8    * to you under the Apache License, Version 2.0 (the
    9    * "License"); you may not use this file except in compliance
    10   * with the License.  You may obtain a copy of the License at
    11   *
    12   *   http://www.apache.org/licenses/LICENSE-2.0
    13   *
    14   * Unless required by applicable law or agreed to in writing,
    15   * software distributed under the License is distributed on an
    16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    17   * KIND, either express or implied.  See the License for the
    18   * specific language governing permissions and limitations
    19   * under the License.
    20   */
    21
    22
    23  // Turbine stuff.
    24
    25  import org.apache.turbine.modules.Screen;
    26  import org.apache.turbine.pipeline.PipelineData;
    27  import org.apache.turbine.util.RunData;
    28
    29  /**
    30   * Base class for writing Screens that output binary data.  This class
    31   * is provided as a helper class for those who want to write Screens
    32   * that output raw binary data.  For example, it may be extended into
    33   * a Screen that outputs a SVG file or a SWF (Flash Player format)
    34   * movie.  The only thing one has to do is to implement the two
    35   * methods <code>getContentType(PipelineData data)</code> and
    36   * <code>doOutput(PipelineData data)</code> (see below).
    37   *
    38   * <p> You might want to take a look at the ImageServer screen class
    39   * contained in the TDK.<br>
    40   *
    41   * @author <a href="mailto:rkoenig@chez.com">Regis Koenig</a>
    42   * @author <a href="mailto:peter@courcoux.biz">Peter Courcoux</a>
    43   * @version $Id: RawScreen.java 1709648 2015-10-20 17:08:10Z tv $
    44   */
    45  public abstract class RawScreen extends Screen
    46  {
    47      /**
    48       * Build the Screen.  This method actually makes a call to the
    49       * doOutput() method in order to generate the Screen content.
    50       *
    51       * @param pipelineData Turbine information.
    52       * @return A ConcreteElement.
    53       * @exception Exception, a generic exception.
    54       */
    55      @Override
    56      protected final String doBuild(PipelineData pipelineData)
    57              throws Exception
    58      {
    59          RunData data = getRunData(pipelineData);
    60          data.getResponse().setContentType(getContentType(pipelineData));
    61          data.declareDirectResponse();
    62          doOutput(pipelineData);
    63          return null;
    64      }
    65
    66      /**
    67       * Set the content type.  This method should be overridden to
    68       * actually set the real content-type header of the output.
    69       *
    70       * @param pipelineData Turbine information.
    71       * @return A String with the content type.
    72       */
    73      protected abstract String getContentType(PipelineData pipelineData);
    74
    75      /**
    76       * Actually output the dynamic content.  The OutputStream can be
    77       * accessed like this: <pre>OutputStream out =
    78       * data.getResponse().getOutputStream();</pre>.
    79       *
    80       * @param pipelineData Turbine information.
    81       * @exception Exception, a generic exception.
    82       */
    83      protected abstract void doOutput(PipelineData pipelineData) throws Exception;
    84
    85      /**
    86       * The layout must be set to null.
    87       *
    88       * @param pipelineData Turbine information.
    89       * @return A null String.
    90       */
    91      @Override
    92      public final String getLayout(PipelineData pipelineData)
    93      {
    94          return null;
    95      }
    96  }