Hi,
I'm new to servlet/JSP programming, and especially connection pooling. I get a null pointer exception when I try to connect to my mysql database. The driver name, user name, and password for the database all work properly when connecting without connection pooling.
Any assistance you can provide would be greatly appreciated. Please let me know if there are any additional files you'd like me to post.
==============================
SOFTWARE:
mysql 4.1.10
tomcat 4.0.1
mysql-connector-java-3.1.7
===============================
ERROR MESSAGE:
java.lang.NullPointerException
at music.cart.CartServlet.doPost(CartServlet.java:46)
at music.cart.CartServlet.doGet(CartServlet.java:84)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.servlets.InvokerServlet.serveRequest(InvokerServlet.java:446)
at org.apache.catalina.servlets.InvokerServlet.doGet(InvokerServlet.java:180)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
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:201)
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)
...
================================
FILE: CartServlet.java
package music.cart;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
import music.business.*;
import music.data.*;
import music.util.*;
public class CartServlet extends HttpServlet{
private MurachPool connectionPool;
public void init() throws ServletException{
connectionPool = MurachPool.getInstance();
}
public void destroy() {
connectionPool.destroy();
}
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException{
String productCode = request.getParameter("productCode");
String quantityAsString = request.getParameter("quantity");
HttpSession session = request.getSession(true);
Cart cart = (Cart) session.getAttribute("cart");
if (cart == null){
cart = new Cart();
session.setAttribute("cart", cart);
}
int quantity = 1;
// If the user enters a negative or invalid number in the
// Update text box, the quantity is automatically reset to 1.
try{
quantity = Integer.parseInt(quantityAsString);
if (quantity < 0) throw new NumberFormatException();
}
catch(NumberFormatException nfe){
quantity = 1;
}
Connection connection = connectionPool.getConnection(); // LINE 46
try{
Product product = ProductDB.readRecord(connection, productCode);
if (product != null){
LineItem lineItem = new LineItem(product, quantity);
if (quantity > 0)
cart.addItem(lineItem);
else
cart.removeItem(lineItem);
//throw new SQLException("test");
}
}
catch(SQLException e){
log("CartServlet SQLException: " + e);
throw new ServletException(e);
}
finally{
connectionPool.freeConnection(connection);
}
session.setAttribute("cart", cart);
// If no items exist in cart, forward to the Index page.
String url = "";
if (cart.getItems().size() <= 0){
url = "/cart/index.jsp";
}
// Otherwise, forward to the Cart page.
else{
url = "/cart/cart.jsp";
}
RequestDispatcher dispatcher =
getServletContext().getRequestDispatcher(url);
dispatcher.forward(request, response);
}
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException{
doPost(request, response);
}
}
=============================================
FILE: MurachPool.java
package music.util;
import com.javaexchange.dbConnectionBroker.*;
import java.io.*;
public class MurachPool extends DbConnectionBroker{
private static MurachPool pool = null;
private MurachPool(String driverName, String dbUrl, String username,
String password, int minConns, int maxConns,
String logFilename, double maxConnTimeInDays)
throws IOException{
super(driverName, dbUrl, username, password,
minConns, maxConns, logFilename, maxConnTimeInDays);
}
public synchronized static MurachPool getInstance(){
try{
if (pool == null){
//System.out.println("Creating the MurachPool object.");
pool = new MurachPool("org.gjt.mm.mysql.Driver",
"jdbc:mysql://localhost/musicTest", "root",
"", 5, 20,
"../webapps/musicStore/connectPool.log",
1.0);
}
}
catch(IOException ioe){
System.err.println("MurachPool IOException: " + ioe);
}
return pool;
}
}
===============================================
FILE: web.xml
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
"http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
<web-app>
<!-- Enable
servlet mapping -->
<!-- To use these, you would need to call the mapped URL
pattern from a
JSP or servlet -->
<servlet>
<servlet-name>EmailServlet</servlet-name>
<servlet-class>music.email.EmailServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>CartServlet</servlet-name>
<servlet-class>music.cart.CartServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>EmailServlet</servlet-name>
<url-pattern>email/email</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>CartServlet</servlet-name>
<url-pattern>cart/cart</url-pattern>
</servlet-mapping>
<!-- Enable basic authentication using the
JDBC realm -->
<!--
<security-constraint>
<web-resource-collection>
<web-resource-name>Basic</web-resource-name>
<url-pattern>/admin/*</url-pattern>
</web-resource-collection>
<auth-constraint>
<role-name>service</role-name>
</auth-constraint>
<user-data-constraint>
<transport-guarantee>NONE</transport-guarantee>
</user-data-constraint>
</security-constraint>
<login-config>
<auth-method>BASIC</auth-method>
</login-config>
-->
</web-app>
===========================
