filterresultservlet.java

esri的ArcGIS Server超级学习模板程序（for java）

package com.esri.solutions.jitk.web.tasks.filter;

import org.apache.log4j.Logger;
import org.apache.log4j.Priority;
import javax.faces.FactoryFinder;
import javax.faces.context.FacesContext;
import javax.faces.context.FacesContextFactory;
import javax.faces.lifecycle.LifecycleFactory;
import javax.faces.lifecycle.Lifecycle;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletOutputStream;

/**
 * MVS-043/45: Filter Task support servlet. This servlet returns the results in xhtml format. 
 */
@SuppressWarnings("serial")
public class FilterResultServlet extends HttpServlet {
	private static Logger logger = Logger.getLogger(FilterResultServlet.class.getName());

	/**
	 * Called by the servlet container to indicate to a servlet 
	 * that the servlet is being placed into service.
	 */
	public void init(ServletConfig config) throws ServletException {
        super.init(config);
    }

    //TODO: Download a CSV export (or file from session memory) is a common operation.
    //      this class should be refactored to a common component and named as such.
	public void doGet(HttpServletRequest request, HttpServletResponse response)
		throws ServletException {
    	try {
			String id = request.getParameter("id");
			String csv_id = request.getParameter("csv_id");
			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(request.getSession().getServletContext(), request, response, lifecycle);
			}

			ServletOutputStream out = response.getOutputStream();
			
			if (id != null) {
				String xml = (String)facesContext.getExternalContext().getSessionMap().get(id);
				out.write(xml.getBytes());
			}
			
			if (csv_id != null) {
				//TODO: Where is the Session memory being released? If the answer is nowhere,
				//      release it at an appropriate place. Do not leak session memory.
				String csv = (String)facesContext.getExternalContext().getSessionMap().get(csv_id);
				
				response.addHeader("Content-Disposition", "attachment; filename=Export.csv");
				response.addHeader("Content-Length", String.valueOf(csv.getBytes().length) );
				response.setContentType("application/octet-stream");
				
				out.write(csv.getBytes());
			}
			
			out.flush();
			out.close();
		}
    	catch (Exception e) {
			logger.log(Priority.ERROR, "Unable to do get", e);
		}
    }
}