IStreamingAction.java

/*
 * This program is free software; you can redistribute it and/or modify it under the 
 * terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software 
 * Foundation.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this 
 * program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html 
 * or from the Free Software Foundation, Inc., 
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; 
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * Copyright 2009 Pentaho Corporation.  All rights reserved.
 *
 */
package org.pentaho.platform.api.action;

import java.io.OutputStream;

import org.pentaho.platform.api.engine.IOutputHandler;
import org.pentaho.platform.api.engine.ISolutionEngine;


/**
 * The interface for Actions that want to stream content to the caller.
 * A "streaming" output is a special type of action definition output that
 * will result in an {@link OutputStream} being set on the Action.  
 * 
 * It is generally recommended that if your Action bean yields any content
 * for user consumption, that it implement {@link IStreamingAction}.  This
 * guarantees that your Action will have the option of:
 * <ul> 
 * <li>streaming the generated content back to the user, such as an HTTP servlet response
 * <li>saving the content to a content repository
 * <li>communicating with existing BI Platform components (such as EmailComponent, which
 * expects to find attachments in the content repository)
 * </ul>
 * <p>
 * From the perspective of the Action Sequence itself, an output is considered 
 * a "streaming" output if the attribute "type" is set to "content", e.g.
 * <code>
 * <myContentOutput type="content"/>
 * </code>
 * The output may or may not have a globally defined destination to which it corresponds.
 * If the output does correspond to a globally defined output with a destination, then
 * the source of the {@link OutputStream} will be determined by the {@link IOutputHandler}
 * provided during the execution of the Action Sequence by the {@link ISolutionEngine}.
 * <p>
 * In the case that an output is considered "streaming", it will basically be
 * treated similar to an input in that it will be set on the Action with a 
 * setter method.  For example, if an action definition declares a streaming
 * output called "reportContent", then the platform will attempt to call a
 * method on the Action called "setReportContentStream(OutputStream os)".  
 * Note that the post-fix "Stream" will be added to the name of your output.
 * Streaming outputs will not be queried once the Action has finished executing
 * like a normal non-streaming output would.
 * @see IAction
 * @author aphillips
 * @since 3.6
 */
public interface IStreamingAction extends IAction {

  /**
   * Requests the mimetype of the content that the Action will write to the
   * provided stream name.  To use the example in the above javadoc, this
   * streamPropertyName would be "reportContent".
   * @param streamPropertyName the action definition output name representing
   * the streamed output, e.g. "reportContent"
   * @return the mimeType for the stream indicated by streamPropertyName
   */
  public String getMimeType(String streamPropertyName);

}