JSP Help Please

Tue, 04 Jun 2002 21:40:39 -0700

Hi All,
I have a servlet that query out some record and forward it to a jsp page to display.  I got an error which I have no clue what it's complaint about.  here is my code.
package Product;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
import java.util.*;
public class ProductAdminServlet extends HttpServlet {
  private static final String driver = "org.gjt.mm.mysql.Driver";
  private static final String user = "webuser";
  private static final String password = "login";
  private static final String dbURL = "jdbc:mysql:///sentry";
  private Connection ObjConnection = null;
  private PreparedStatement getStmt = null;
  private ServletContext context;
 
  public void init(ServletConfig config) throws ServletException {
    super.init(config);
    context = config.getServletContext();
    try {
      Class.forName(driver);
      ObjConnection = DriverManager.getConnection(dbURL, user, password);
    }
    catch (ClassNotFoundException e) {
      System.err.println("Unable to load database driver");
      throw new ServletException("Unable to load database driver");
    }
    catch (SQLException e) {
      System.err.println("Unable to connect to database");
      throw new ServletException("Unable to connect to database");
    }
  }
 
  public void service(HttpServletRequest req,
        HttpServletResponse res)
    throws ServletException, IOException {
    String jsp = "";
    String cmd = req.getParameter("cmd");
    String idString = req.getParameter("id");
    int id;
    try { id = Integer.parseInt(idString); }
    catch(NumberFormatException e) { id=0; };
    //Get Product By ID
    if (cmd.equals("get")) {
      ProductBean product = getProductByID(1);
      req.setAttribute("product", product);
      jsp = "/list.jsp";
    }
    //Get All Products
    if (cmd.equals("getall")){
      Vector list = getAllProduct();
      req.setAttribute("list", list);
      jsp = "/product_list.jsp";
    }
   
    RequestDispatcher dispatcher;
    dispatcher = context.getRequestDispatcher(jsp);
    dispatcher.forward(req, res);
  }
 
  //This method will return a single record base on the id
  public ProductBean getProductByID(int id) {
    try {
      ResultSet results;
      synchronized (getStmt) {
 getStmt.clearParameters();
        getStmt = ObjConnection.prepareStatement("SELECT * FROM Product WHERE Product_ID=?");
 getStmt.setInt(1, 1);
 results = getStmt.executeQuery();
      }
      ProductBean product = null;
      if (results.next()) {
 product = makeBean(results);
      }
      if (results != null)
 results.close();
      return product;
    }
    catch (SQLException se) { return null; }
  }
 
  public Vector getAllProduct() {
    try {
      Vector list = new Vector();
      ResultSet results;
      Statement st = ObjConnection.createStatement();
      results = st.executeQuery("SELECT * FROM Product");
      while (results.next())
 list.add(makeBean(results));
      return list;
    }
    catch (SQLException se) { return null; }
  }
 
  //This method will take a record and turn it into the bean
  public ProductBean makeBean(ResultSet results)
    throws SQLException {
    ProductBean product = new ProductBean();
    product.setProductCode(results.getString("Product_Code"));
    product.setProductType(results.getString("Product_Type"));
    product.setProductDescription(results.getString("Product_Description"));
    product.setProductForwardBalance(results.getInt("Product_Balance"));
    product.setProductUnitPrice(results.getDouble("Product_Unit_Price"));
    product.setProductUnitMeasure(results.getString("Product_Unit_Measure"));
    product.setProductSellByYard(results.getInt("Product_Sell_By_Yard"));
    //Return the product result
    return product;
  }
  //Release Resources
  public void destroy() {
    try {
      if (ObjConnection != null)
         ObjConnection.close();
    }
    catch (SQLException e) { }
  }
}
 
JSP Code
 

<%@ page import="java.util.*" %>
<jsp:useBean id="product" class="Product.ProductBean" scope="request"/>
<html>
<body>
<table width="600" border="0">
  <tr bgcolor="#006699">
    <td colspan="6" class="big_label">PRODUCTS ADMINISTRATION</td>
  </tr>
  <tr bgcolor="#000000">
    <td width="100" class="table_label">&nbsp;</td>
    <td width="100" class="table_label">Product Code</td>
    <td width="100" class="table_label">Product Type</td>
    <td width="100" class="table_label">Description</td>
    <td width="100" class="table_label">Balance</td>
    <td width="100" class="table_label">Unit Price</td>
  </tr>
<%
  Vector v = (Vector)request.getAttribute("list");
  Iterator i= v.iterator();
  while (i.hasNext()) {
     product = (Product.ProductBean)i.next();
%>
  <tr>
    <td class="table_data">&nbsp;</td>
    <td class="table_data"><jsp:getProperty name="product"  property="productCode" /></td>
    <td class="table_data"><jsp:getProperty name="product"  property="productType" /></td>
    <td class="table_data"><jsp:getProperty name="product"  property="productDescription" /></td>
    <td class="table_data"><jsp:getProperty name="product"  property="productForwardBalance" /></td>
    <td class="table_data"><jsp:getProperty name="product"  property="productUnitPrice" /></td>
  </tr>
<% } %>
  <tr bgcolor="#006699">
    <td colspan="6">&nbsp;</td>
  </tr>
</table>
</body>
</html>
 

type Exception report

message Internal Server Error

description The server encountered an internal error (Internal Server Error) that prevented it from fulfilling this request.

exception 

java.lang.NullPointerException
        at org.apache.jsp.product_0005flist$jsp._jspService(product_0005flist$jsp.java:94)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:107)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
        at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:202)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:382)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:474)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:683)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:431)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:355)
        at Product.ProductAdminServlet.service(ProductAdminServlet.java:61)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243)
        at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190)
        at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
        at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246)
        at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
        at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2343)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
        at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
        at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)
        at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170)
        at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:468)
        at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
        at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
        at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1012)
        at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1107)
        at java.lang.Thread.run(Thread.java:536)

Can someone help me out please
Thanks,
Duc

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