jstljsp include servlet使jsp为空

o4hqfura  于 2021-06-17  发布在  Mysql
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我正在编写一段代码来显示来自mysql数据库的组织列表。我使用的是jdbc领域表单身份验证，因此我知道我的数据库可以被查询并正常运行。当我排除servlet时，我的jsp页面会像普通页面一样显示所有内容，但是当我包含servlet时，我的页面会显示空白，只有css的背景色，没有其他内容。我非常感谢您能帮助我找出发生这种情况的原因和/或解决方法，以便我可以从数据库中显示此列表。所有相关代码如下：
有问题的jsp页面：

  1. <%@page import="SW.models.StudentOrg"%>
  2. <%@page contentType="text/html" pageEncoding="utf-8"%>
  3. <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
  4. <jsp:include page="GetOrgServlet" flush="true" />
  5. <c:import url="/includes/header.html" />
  6. <body>
  7.     <div id='container'>
  9.         <c:import url="/includes/navigation.html" />
  11.         <aside>
  12.             <img src='https://projecthelping.org/wp-content/uploads/2017/11/Your-Logo-here.png' width="200" height="200"   alt='Organization Logo'>
  13.             <h3>[List of Upcoming Events Here]</h3>
  14.             <p>[Contact Information Here]</p>
  15.         </aside>
  17.         <section id='main'>
  19.             <h2>[Student Organization Name Here]</h2>   
  20.             <p>
  21.                 [Student Organization Description Here] 
  22.             </p>
  24.             <p>
  25.                 [Student Organizations Q&A Section Here]
  26.             </p>
  28.             <table>
  29.                 <th>Org ID</th>
  30.                 <th>Org Name</th>
  31.                 <th>Org Description</th>
  32.                     <c:forEach var="studentOrg" items="${studentOrgList.studentOrg}"> 
  33.                     <tr>
  34.                         <td>${studentOrg.OrgID}</td>
  35.                         <td>${studentOrg.OrgName}</td>
  36.                         <td>${studentOrg.OrgDescription}</td>
  37.                     </tr>
  38.                 </c:forEach>
  39.             </table>
  41.         </section>
  43.         <c:import url="/includes/footer.jsp" />
  45.     </div>
  46. </body>
  47. </html>

有问题的servlet：

  1. package SW.controllers;
  3. import java.io.IOException;
  4. import javax.servlet.ServletException;
  5. import javax.servlet.http.HttpServlet;
  6. import javax.servlet.http.HttpServletRequest;
  7. import javax.servlet.http.HttpServletResponse;
  8. import javax.servlet.http.HttpSession;
  9. import SW.data.DB;
  10. import SW.models.StudentOrg;
  11. import SW.models.StudentOrgList;
  13. public class GetOrgServlet extends HttpServlet {
  15.     /**
  16.      * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
  17.      * methods.
  18.      *
  19.      * @param request servlet request
  20.      * @param response servlet response
  21.      * @throws ServletException if a servlet-specific error occurs
  22.      * @throws IOException if an I/O error occurs
  23.      */
  24.     protected void processRequest(HttpServletRequest request, HttpServletResponse response)
  25.             throws ServletException, IOException {
  27.         HttpSession session = request.getSession();
  28.         StudentOrgList studentOrgList = DB.getStudentOrgs();
  29.         session.setAttribute("studentOrgList", studentOrgList);
  31.     }
  33.     // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
  34.     /**
  35.      * Handles the HTTP <code>GET</code> method.
  36.      *
  37.      * @param request servlet request
  38.      * @param response servlet response
  39.      * @throws ServletException if a servlet-specific error occurs
  40.      * @throws IOException if an I/O error occurs
  41.      */
  42.     @Override
  43.     protected void doGet(HttpServletRequest request, HttpServletResponse response)
  44.             throws ServletException, IOException {
  45.         processRequest(request, response);
  46.     }
  48.     /**
  49.      * Handles the HTTP <code>POST</code> method.
  50.      *
  51.      * @param request servlet request
  52.      * @param response servlet response
  53.      * @throws ServletException if a servlet-specific error occurs
  54.      * @throws IOException if an I/O error occurs
  55.      */
  56.     @Override
  57.     protected void doPost(HttpServletRequest request, HttpServletResponse response)
  58.             throws ServletException, IOException {
  59.         processRequest(request, response);
  61.     }
  63.     /**
  64.      * Returns a short description of the servlet.
  65.      *
  66.      * @return a String containing servlet description
  67.      */
  68.     @Override
  69.     public String getServletInfo() {
  70.         return "Short description";
  71.     }// </editor-fold>
  73. }

java（在存储查询的地方，我在servlet中使用getstudentorgs）

  1. package SW.data;
  3. import java.sql.*;
  4. import SW.models.*;
  6. public class DB {
  8.     public static StudentOrg selectStudentOrg(Integer OrgID) {
  9.         ConnectionPool pool = ConnectionPool.getInstance();
  10.         Connection connection = pool.getConnection();
  11.         PreparedStatement ps = null;
  12.         ResultSet rs = null;
  14.         String query = "SELECT * FROM org "
  15.                 + "WHERE OrgID = ?";
  16.         try {
  17.             ps = connection.prepareStatement(query);
  18.             ps.setInt(1, OrgID);
  19.             rs = ps.executeQuery();
  20.             StudentOrg studentOrg = null;
  21.             if (rs.next()) {
  22.                 studentOrg = new StudentOrg();
  23.                 studentOrg.setOrgID(rs.getInt("orgID"));
  24.                 studentOrg.setOrgName(rs.getString("orgName"));
  25.                 studentOrg.setOrgDescription(rs.getString("orgDescription"));
  26.             }
  27.             return studentOrg;
  28.         } catch (SQLException e) {
  29.             System.out.println(e);
  30.             return null;
  31.         } finally {
  32.             DBUtil.closeResultSet(rs);
  33.             DBUtil.closePreparedStatement(ps);
  34.             pool.freeConnection(connection);
  35.         }
  36.     }
  38.     public static StudentOrgList getStudentOrgs() {
  39.         ConnectionPool pool = ConnectionPool.getInstance();
  40.         Connection connection = pool.getConnection();
  41.         PreparedStatement ps = null;
  42.         ResultSet rs = null;
  44.         String query = "SELECT * FROM org";
  45.         try {
  46.             ps = connection.prepareStatement(query);
  47.             rs = ps.executeQuery();
  48.             StudentOrgList studentOrgList = new StudentOrgList();
  49.             while (rs.next()) {
  50.                 StudentOrg studentOrg = new StudentOrg();
  51.                 studentOrg.setOrgID(rs.getInt("OrgID"));
  52.                 studentOrg.setOrgName(rs.getString("OrgName"));
  53.                 studentOrg.setOrgDescription(rs.getString("OrgDescription"));
  54.                 studentOrgList.addStudentOrg(studentOrg);
  55.             }
  56.             return studentOrgList;
  57.         } catch (SQLException e) {
  58.             System.err.println(e);
  59.             return null;
  60.         } finally {
  61.             DBUtil.closeResultSet(rs);
  62.             DBUtil.closePreparedStatement(ps);
  63.             pool.freeConnection(connection);
  64.         }
  65.     }
  66. }

正在查询的表的图片
连接池

  1. package SW.data;
  3. import java.sql.*;
  4. import javax.sql.DataSource;
  5. import javax.naming.InitialContext;
  6. import javax.naming.NamingException;
  8. public class ConnectionPool {
  10.     private static ConnectionPool pool = null;
  11.     private static DataSource dataSource = null;
  13.     private ConnectionPool() {
  14.         try {
  15.             InitialContext ic = new InitialContext();
  16.             dataSource = (DataSource) ic.lookup("java:/comp/env/jdbc/milestone3");
  17.         } catch (NamingException e) {
  18.             System.out.println(e);
  19.         }
  20.     }
  22.     public static synchronized ConnectionPool getInstance() {
  23.         if (pool == null) {
  24.             pool = new ConnectionPool();
  25.         }
  26.         return pool;
  27.     }
  29.     public Connection getConnection() {
  30.         try {
  31.             return dataSource.getConnection();
  32.         } catch (SQLException e) {
  33.             System.out.println(e);
  34.             return null;
  35.         }
  36.     }
  38.     public void freeConnection(Connection c) {
  39.         try {
  40.             c.close();
  41.         } catch (SQLException e) {
  42.             System.out.println(e);
  43.         }
  44.     }
  45. }

数据库工具

  1. package SW.data;
  3. import java.sql.*;
  5. public class DBUtil {
  7.     public static void closeStatement(Statement s) {
  8.         try {
  9.             if (s != null) {
  10.                 s.close();
  11.             }
  12.         } catch (SQLException e) {
  13.             System.out.println(e);
  14.         }
  15.     }
  17.     public static void closePreparedStatement(Statement ps) {
  18.         try {
  19.             if (ps != null) {
  20.                 ps.close();
  21.             }
  22.         } catch (SQLException e) {
  23.             System.out.println(e);
  24.         }
  25.     }
  27.     public static void closeResultSet(ResultSet rs) {
  28.         try {
  29.             if (rs != null) {
  30.                 rs.close();
  31.             }
  32.         } catch (SQLException e) {
  33.             System.out.println(e);
  34.         }
  35.     }
  36. }

再说一次，我不一定要这样显示列表，这只是一种方法，我以为我知道怎么做，因为我以前这么做了，但似乎有些不对劲，我找不到它的任何地方。因此，我很感激任何关于这个解决方案或不同的建议！

Javamysqljspmodel-view-controllerjstl

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