listpersonservlet.java

SUN的JAVA EE5源代码java_ee_sdk-5_03-preview-samples

/*
 * The contents of this file are subject to the terms 
 * of the Common Development and Distribution License 
 * (the License).  You may not use this file except in
 * compliance with the License.
 * 
 * You can obtain a copy of the license at 
 * https://glassfish.dev.java.net/public/CDDLv1.0.html or
 * glassfish/bootstrap/legal/CDDLv1.0.txt.
 * See the License for the specific language governing 
 * permissions and limitations under the License.
 * 
 * When distributing Covered Code, include this CDDL 
 * Header Notice in each file and include the License file 
 * at glassfish/bootstrap/legal/CDDLv1.0.txt.  
 * If applicable, add the following below the CDDL Header, 
 * with the fields enclosed by brackets [] replaced by
 * you own identifying information: 
 * "Portions Copyrighted [year] [name of copyright owner]"
 * 
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 */
package enterprise.web_jpa_war.servlet;

import java.io.*;
import java.util.List;
import javax.servlet.*;
import javax.servlet.http.*;

import javax.persistence.PersistenceUnit;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityManager;

/**
 * The servlet class to list Persons from database
 */
public class ListPersonServlet extends HttpServlet {
    
    @PersistenceUnit
    private EntityManagerFactory emf;
    
    /** Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        assert emf != null;  //Make sure injection went through correctly.
        EntityManager em = null;
        try {
            em = emf.createEntityManager();

            //query for all the persons in database
            List persons = em.createQuery("select p from Person p").getResultList();
            request.setAttribute("personList",persons);
            
            //Forward to the jsp page for rendering
            request.getRequestDispatcher("ListPerson.jsp").forward(request, response);
        } catch (Exception ex) {
            throw new ServletException(ex);
        } finally {
            //close the em to release any resources held up by the persistebce provider
            em.close();
        }
      
    }
    
    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }
    
    /** Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }
    
    /** Returns a short description of the servlet.
     */
    public String getServletInfo() {
        return "ListPerson servlet";
    }
    // </editor-fold>
}