cewolfrenderer.java

cewolf是个一个自动报表程序

/* ================================================================
 * Cewolf : Chart enabling Web Objects Framework
 * ================================================================
 *
 * Project Info:  http://cewolf.sourceforge.net
 * Project Lead:  Guido Laures ([e-mail]);
 *
 * (C) Copyright 2002, by Guido Laures
 *
 * This library is free software; you can redistribute it and/or modify it under the terms
 * of the GNU Lesser General Public License as published by the Free Software Foundation;
 * either version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 */

package de.laures.cewolf;

import java.io.IOException;
import java.io.OutputStream;
import java.io.Writer;
import java.util.Enumeration;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import de.laures.cewolf.util.RenderingHelper;

/**
 * The rendering servlet of Cewolf. It is resposible for writing an entire chart
 * img into the response stream of the client. Everything needed for this is
 * prepared already by the ChartImgTag resp. LegendTag. The ID of a chart image
 * is passed to this servlet as a request parameter. After that the image object
 * is retrieved from the server side session based image cache. This servlet
 * must be configured in web.xml of the web application in order to use Cewolf
 * services. The servlet's URL relative to the web apps root is used as the
 * renderer attribute of the ChartImgTag resp. LegendTag in the JSP page.
 * 
 * @see de.laures.cewolf.taglib.tags.ChartImgTag
 * @see de.laures.cewolf.taglib.tags.LegendTag
 * @author Guido Laures
 * @since 0.1
 */
public class CewolfRenderer extends HttpServlet implements WebConstants
{

  public static final String  INIT_CONFIG  = "CewolfRenderer_Init_Config";
  private static final String STATE        = "state";
  private boolean             debugged     = false;
  private int                 requestCount = 0;
  private Configuration       config       = null;

  public void init( ServletConfig servletCfg ) throws ServletException
  {
    super.init(servletCfg);
    
    //Store init config params for processing by the Configuration
    servletCfg.getServletContext().setAttribute(INIT_CONFIG, servletCfg);
    config = Configuration.getInstance(servletCfg.getServletContext());
    
    if (config != null)
      this.debugged = config.isDebugged();
    else
      this.debugged = false;
  }

  /**
   * Processes HTTP <code>GET</code> request. Renders the chart or the lengend
   * into the client's response stream.
   * 
   * @param request
   *          servlet request
   * @param response
   *          servlet response
   * @throws ServletException
   *           when the production of data could not be handled by the
   *           configured DatasetProcuder
   */
  
  public synchronized void printParameters(HttpServletRequest request)
  {
    Enumeration enum = request.getParameterNames();
    while (enum.hasMoreElements())
    {
      String cur = (String)enum.nextElement();
      Object obj = request.getParameter(cur);
      
      log("Request Parameter -> " + cur + " Value -> " + obj.toString());
    }
  }
  
  protected void doGet( HttpServletRequest request, HttpServletResponse response ) throws ServletException, IOException
  {
    if ( debugged )
    {
      logRequest(request);
    }
    addHeaders(response);
    if ( request.getParameter(STATE) != null || !request.getParameterNames().hasMoreElements() )
    {
      requestState(response);
      return;
    }
    requestCount++;
    int width = 400;
    int height = 400;
    if ( request.getParameter(WIDTH_PARAM) != null )
    {
      width = Integer.parseInt(request.getParameter(WIDTH_PARAM));
    }
    if ( request.getParameter(HEIGHT_PARAM) != null )
    {
      height = Integer.parseInt(request.getParameter(HEIGHT_PARAM));
    }

    // determine the cache key
    String imgKey = request.getParameter(IMG_PARAM);
    if ( imgKey == null )
    {
      logAndRenderException(new ServletException("no '" + IMG_PARAM + "' parameter provided for Cewolf servlet."), response, width, height);
      return;
    }
    Storage storage = config.getStorage();
    ChartImage chartImage = storage.getChartImage(imgKey, request);
    if ( chartImage == null )
    {
      renderImageExpiry(response, width, height);
      return;
    }
    // send the img
    try
    {
      long start = System.currentTimeMillis();
      // response.setContentType(cid.getMimeType());
      final int size = chartImage.getSize();
      response.setContentType(chartImage.getMimeType());
      response.setContentLength(size);
      response.setBufferSize(size);
      response.setStatus(HttpServletResponse.SC_OK);
      response.getOutputStream().write(chartImage.getBytes());
      long last = System.currentTimeMillis() - start;
      if ( debugged )
      {
        log("creation time for chart " + imgKey + ": " + last + "ms.");
      }
    }
    catch (Throwable t)
    {
      logAndRenderException(t, response, width, height);
    }
  }

  /**
   * Method addHeaders.
   * 
   * @param response
   */
  private void addHeaders( HttpServletResponse response )
  {
    response.setDateHeader("Expires", System.currentTimeMillis());
  }

  /**
   * Method requestState.
   * 
   * @param request
   * @param response
   */
  private void requestState( HttpServletResponse response ) throws IOException
  {
    Writer writer = response.getWriter();
    writer.write("<HTML><BODY>");
    /*
     * StateDescriptor sd = (StateDescriptor)
     * ChartImageCacheFactory.getChartImageBase( getServletContext());
     * writer.write(HTMLStateTable.getStateTable(sd));
     */
    writer.write("<b>Cewolf servlet up and running.</b><br>");
    writer.write("Requests served so far: " + requestCount);
    writer.write("</HTML></BODY>");
    writer.close();
  }

  private void logAndRenderException( Throwable ex, HttpServletResponse response, int width, int height ) throws IOException
  {
    log(ex.getMessage(), ex);
    response.setContentType("image/jpg");
    OutputStream out = response.getOutputStream();
    RenderingHelper.renderException(ex, width, height, out);
    out.close();
  }

  /**
   * Method renderImageExpiry.
   * 
   * @param response
   * @param width
   * @param height
   */
  private void renderImageExpiry( HttpServletResponse response, int width, int height ) throws IOException
  {
    response.setContentType("image/jpg");
    OutputStream out = response.getOutputStream();
    RenderingHelper.renderMessage("This chart has expired. Please reload.", width, height, out);
    out.close();
  }

  private void logRequest( HttpServletRequest request ) throws IOException
  {
    log("Cewolf request:");
    log("Actual Request values:");
    printParameters(request);
    Enumeration headerNames = request.getHeaderNames();
    while ( headerNames.hasMoreElements() )
    {
      String name = (String) headerNames.nextElement();
      Enumeration values = request.getHeaders(name);
      StringBuffer value = new StringBuffer();
      while ( values.hasMoreElements() )
      {
        value.append((String) values.nextElement() + ",");
      }
      // cut last comma
      if ( value.length() > 0 )
        value.setLength(value.length() - 1);
      log(name + ": " + value);
    }
  //  InputStream body = request.getInputStream();
 //   byte[] bodyData = new byte[body.available()];
 //   body.read(bodyData);
 //   body.close();
 //   log(new String(bodyData));

  }

}