maptemplatepreviewservlet.java

esri的ArcGIS Server超级学习模板程序（for java）

package com.esri.solutions.jitk.common.templates.map;

import java.awt.image.RenderedImage;
import java.awt.image.renderable.ParameterBlock;
import java.io.File;
import java.io.IOException;
import java.text.MessageFormat;

import javax.faces.FactoryFinder;
import javax.faces.context.FacesContext;
import javax.faces.context.FacesContextFactory;
import javax.faces.el.ValueBinding;
import javax.faces.lifecycle.Lifecycle;
import javax.faces.lifecycle.LifecycleFactory;
import javax.media.jai.JAI;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;

/**
 * Generates the Map Template Preview for a specified Map Template.  This servlet needs
 * to be configured with path-style URL mappings and not extension-style mappings.  This
 * servlet expects the URL to be configured like the following:
 * 
 * <code>http://host/Viewer/maptemplate/<Map Template Repo Bean Name>/<Map Template ID>.<format> where
 * 
 * <ul>
 * 	<li>Map Template Repo Bean Name is the name of the Map Template Repository bean name within the
 * 		bean framework.</li>
 *	<li>Map Template ID is the ID of the Map Template</li>
 *  <li>format is the image format, jpg or png.
 * </ul>
 * 
 * In this example, this servlet would need to be mapped to /maptemplate/* URL patterns.
 * 
 * <p>
 * This servlet will send a 404 (Not Found) response if any of the conditions are met:
 * 	<ul>
 * 		<li>Map Template Repository can't be found.
 * 		<li>Map Template with the specified ID can't be found.
 * 	</ul>
 * </p>
 */
 public class MapTemplatePreviewServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet {

	 private static final Logger LOG = LogManager.getLogger(MapTemplatePreviewServlet.class);
	 
	 private static final String ERROR_CANNOT_FIND_TEMPLATE = "Map Template Repository [{0}] does not contain Map Template [{1}]";
	 private static final String ERROR_CANNOT_FIND_REPO = "Cannot find Map Template Repository [{0}]";
	 private static final String WARN_UNRECOGNIZABLE_CONTENT_TYPE = "Unrecognizable Content Type, using default {0}";
	 private static final String WARN_UNSUPPORTED_ENCODING = "{0} is an unsupported encoding, using default {1}";
	 private static final String INFO_MAP_TEMPLATE_ID = "Map Template ID: {0}";
	 private static final String INFO_MAP_TEMPLATE_ID_WITH_EXT = "Map Template ID with Extension: {0}";
	 private static final String INFO_MAP_TEMPLATE_REPO = "Map Template Repository: {0}";
	 private static final String INFO_EXTENSION = "Extension: {0}";
	 
	 private static final String DEFAULT_EXT = "jpg";
	 private static final String DEFAULT_CONTENT_TYPE = "image/jpg";
	 private static final String SUPPORTED_ENCODINGS = "jpg,png";
	 
	 private static final long serialVersionUID = -3637754480378538291L;
	 
	  	
	 /* (non-Java-doc)
	  * @see javax.servlet.http.HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	  */
	 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		 File pathInfo = new File(request.getPathInfo());
		 String repoName = pathInfo.getParent().replace(File.separator, "");
		 String idWithExt = pathInfo.getName().replace(repoName, "");
		 String id = idWithExt.substring(0, idWithExt.lastIndexOf("."));
		 String ext = idWithExt.substring(idWithExt.lastIndexOf(".") + 1);
		 
		 if (LOG.isInfoEnabled()) {
			 LOG.info(MessageFormat.format(INFO_MAP_TEMPLATE_REPO, repoName));
			 LOG.info(MessageFormat.format(INFO_MAP_TEMPLATE_ID_WITH_EXT, idWithExt));
			 LOG.info(MessageFormat.format(INFO_MAP_TEMPLATE_ID, id));
			 LOG.info(MessageFormat.format(INFO_EXTENSION, ext));
		 }
		 
		 IMapTemplateRepository repo = getMapTemplateRepository(repoName, request, response);
		 if (repo == null) {
			 LOG.error(MessageFormat.format(ERROR_CANNOT_FIND_REPO, repoName));
			 log(MessageFormat.format(ERROR_CANNOT_FIND_REPO, repoName));
			 response.sendError(HttpServletResponse.SC_NOT_FOUND);
			 return;
		 }
		
		 IMapTemplate template = repo.getMapTemplate(id);
		 if (template == null) {
			 LOG.error(MessageFormat.format(ERROR_CANNOT_FIND_TEMPLATE, repoName, id));
			 log(MessageFormat.format(ERROR_CANNOT_FIND_TEMPLATE, repoName, id));
			 response.sendError(HttpServletResponse.SC_NOT_FOUND);
			 return;
		 }
		 
		 if (!SUPPORTED_ENCODINGS.contains(ext)) {
			 LOG.warn(MessageFormat.format(WARN_UNSUPPORTED_ENCODING, ext, DEFAULT_EXT));
			 ext = DEFAULT_EXT;
			 idWithExt = id + "." + DEFAULT_EXT;
		 }
		 
		 String contentType = getServletContext().getMimeType(idWithExt);
		 
		 if (contentType == null) {
			 LOG.warn(MessageFormat.format(WARN_UNRECOGNIZABLE_CONTENT_TYPE, DEFAULT_CONTENT_TYPE));
			 contentType = DEFAULT_CONTENT_TYPE;
			 ext = DEFAULT_EXT;
		 }
		 
		 RenderedImage image = template.getPreview();
		 response.setContentType(contentType);
		 
		 ParameterBlock pb = new ParameterBlock();
		 pb.addSource(image);
		 pb.add(response.getOutputStream());
		 pb.add(getJAIEncodingType(ext));
		 
		 JAI.create("encode", pb);
	 }

	 /**
	  * Returns the Map Template Repository with the specified name in the
	  * Faces subsystem.
	  * 
	  * @param repoName	Name of Map Template Repository bean.
	  * @param request	Reference to HTTP Request object.
	  * @param response Reference to HTTP Response object.
	  * @return Reference to Map Template Repository.
	  */
	private IMapTemplateRepository getMapTemplateRepository(String repoName,
			HttpServletRequest request, HttpServletResponse response) {
		
		 FacesContext fc = getFacesContext(request, response);
		 ValueBinding vb = fc.getApplication().createValueBinding("#{" + repoName + "}");
		 IMapTemplateRepository repo = (IMapTemplateRepository) vb.getValue(fc);
		 return repo;
	}
	 
	/**
	 * Helper method to retrieve the {@link FacesContext} object for the
	 * HTTP request.  The FacesContext is used to get references to
	 * managed beans defined in the Faces subsystem.
	 * 
	 * @param request	Reference to HTTP Request object
	 * @param response  Reference to HTTP Response object.
	 * @return Reference to Faces Context object.
	 */
	 private FacesContext getFacesContext (HttpServletRequest request, HttpServletResponse response) {
		 FacesContext facesContext = FacesContext.getCurrentInstance();
		 if (facesContext == null){
			 FacesContextFactory contextFactory = (FacesContextFactory)FactoryFinder.getFactory(FactoryFinder.FACES_CONTEXT_FACTORY);
			 LifecycleFactory lifecycleFactory = (LifecycleFactory)FactoryFinder.getFactory(FactoryFinder.LIFECYCLE_FACTORY);
			 Lifecycle lifecycle = lifecycleFactory.getLifecycle(LifecycleFactory.DEFAULT_LIFECYCLE);

			 facesContext = contextFactory.getFacesContext(this.getServletContext(), request, response, lifecycle);
		 }
		 return facesContext;
	 }
	 
	 /**
	  * Helper method to convert between an image file extension to the
	  * proper encoding type for JAI.  Most notably, it converts "jpg" to
	  * "jpeg".
	  * 
	  * @param ext	Image file extension to convert to JAI encoding type.
	  * @return JAI Encoding Type for image file extension.
	  */
	 private String getJAIEncodingType (String ext) {
		 if (ext.equalsIgnoreCase("jpg")) {
			 return "jpeg";
		 }
		 return ext;
	 }
}