Java tutorial
package nextapp.echo.chart.webcontainer.service; /* * This file is part of the Echo3 Chart Library. * Copyright (C) 2005 NextApp, Inc. * * Version: MPL 1.1/GPL 2.0/LGPL 2.1 * * The contents of this file are subject to the Mozilla Public License Version * 1.1 (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.mozilla.org/MPL/ * * Software distributed under the License is distributed on an "AS IS" basis, * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License * for the specific language governing rights and limitations under the * License. * * Alternatively, the contents of this file may be used under the terms of * either the GNU General Public License Version 2 or later (the "GPL"), or * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), * in which case the provisions of the GPL or the LGPL are applicable instead * of those above. If you wish to allow use of your version of this file only * under the terms of either the GPL or the LGPL, and not to allow others to * use your version of this file under the terms of the MPL, indicate your * decision by deleting the provisions above and replace them with the notice * and other provisions required by the GPL or the LGPL. If you do not delete * the provisions above, a recipient may use your version of this file under * the terms of any one of the MPL, the GPL or the LGPL. */ import java.awt.Point; import java.awt.geom.Point2D; import java.awt.image.BufferedImage; import java.io.IOException; import java.io.OutputStream; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import nextapp.echo.app.Extent; import nextapp.echo.chart.app.ChartDisplay; import nextapp.echo.chart.webcontainer.sync.component.ChartDisplayPeer; import nextapp.echo.webcontainer.Connection; import nextapp.echo.webcontainer.ContentType; import nextapp.echo.webcontainer.Service; import nextapp.echo.webcontainer.UserInstance; import nextapp.echo.webcontainer.WebContainerServlet; import nextapp.echo.webcontainer.util.PngEncoder; import org.jfree.chart.ChartRenderingInfo; import org.jfree.chart.JFreeChart; import org.jfree.chart.entity.EntityCollection; /** * <code>Service</code> to render chart images. */ public class ChartImageService implements Service { /** * The service id. */ private static final String SERVICE_ID = "Echo.RemoteClient.Chart.ChartImageService"; /** * Parameter keys used in generating service URI. */ private static final String[] URI_PARAMETER_KEYS = { "chartId", "v" }; /** * A version property which is ignored on the server but which forces the browser to * reload the image. */ private int version = 0; /** * Returns the appropriate URI to display a chart for a specific * <code>ChartDisplay</code> component. * * @param rc the relevant <code>RenderContext</code> * @param chartDisplay the rendering <code>ChartDisplay</code> * @param version the version number of the chart * (incremented when chart is re-rendered due to an update) * @return the URI */ public String createUri(UserInstance userInstance, ChartDisplay chartDisplay) { return userInstance.getServiceUri(INSTANCE, URI_PARAMETER_KEYS, new String[] { chartDisplay.getRenderId(), String.valueOf(++version) }); } /** * Singleton instance. */ private static final ChartImageService INSTANCE = new ChartImageService(); static { WebContainerServlet.getServiceRegistry().add(INSTANCE); } /** Self-instantiated singleton. */ private ChartImageService() { } public String getId() { return SERVICE_ID; } public int getVersion() { return DO_NOT_CACHE; } public void service(Connection conn) throws IOException { try { UserInstance userInstance = (UserInstance) conn.getUserInstance(); if (userInstance == null) { serviceBadRequest(conn, "No container available."); return; } HttpServletRequest request = conn.getRequest(); String chartId = request.getParameter("chartId"); ChartDisplay chartDisplay = (ChartDisplay) userInstance.getApplicationInstance() .getComponentByRenderId(chartId); synchronized (chartDisplay) { if (chartDisplay == null || !chartDisplay.isRenderVisible()) { throw new IllegalArgumentException("Invalid chart id."); } Extent ewidth = (Extent) chartDisplay.getRenderProperty(ChartDisplay.PROPERTY_WIDTH); int width = ewidth != null ? ewidth.getValue() : ChartDisplayPeer.DEFAULT_WIDTH; Extent eheight = (Extent) chartDisplay.getRenderProperty(ChartDisplay.PROPERTY_HEIGHT); int height = ewidth != null ? eheight.getValue() : ChartDisplayPeer.DEFAULT_HEIGHT; JFreeChart chart = chartDisplay.getChart(); BufferedImage image; ChartRenderingInfo info = new ChartRenderingInfo(); synchronized (chart) { image = chart.createBufferedImage(width, height, info); } // EntityCollection coll = info.getEntityCollection(); // debug("About to show entities"); // for (int i = 0; i < coll.getEntityCount(); i++) { // debug("Entity: " + coll.getEntity(i).getShapeCoords()); // debug("Entity: " + coll.getEntity(i).getShapeType()); // debug("Entity: " + coll.getEntity(i).getToolTipText()); // } PngEncoder encoder = new PngEncoder(image, true, null, 3); conn.setContentType(ContentType.IMAGE_PNG); OutputStream out = conn.getOutputStream(); encoder.encode(out); } } catch (IOException ex) { // Internet Explorer appears to enjoy making half-hearted requests for images, wherein it resets the connection // leaving us with an IOException. This exception is silently eaten. ex.printStackTrace(); } } private void debug(String s) { System.out.println(s); } /** * Sets the response status indicating that a bad request * was made to this service. * @param conn the connection. * @param message the error message. */ private void serviceBadRequest(Connection conn, String message) { conn.getResponse().setStatus(HttpServletResponse.SC_BAD_REQUEST); conn.setContentType(ContentType.TEXT_PLAIN); conn.getWriter().write(message); } /** * Returns an instance for public use. * @return an instance for public use. */ public static ChartImageService getInstance() { return INSTANCE; } }