Mega Code Archive
Servlet Database Connection
<![CDATA[
import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
class ConnectionHolder implements HttpSessionBindingListener {
private Connection con = null;
public ConnectionHolder(Connection con) {
// Save the Connection
this.con = con;
try {
con.setAutoCommit(false); // transactions can extend between web pages!
}
catch(SQLException e) {
// Perform error handling
}
}
public Connection getConnection() {
return con; // return the cargo
}
public void valueBound(HttpSessionBindingEvent event) {
// Do nothing when added to a Session
}
public void valueUnbound(HttpSessionBindingEvent event) {
// Roll back changes when removed from a Session
// (or when the Session expires)
try {
if (con != null) {
con.rollback(); // abandon any uncomitted data
con.close();
}
}
catch (SQLException e) {
// Report it
}
}
}
/* Actual Servlet */
public class MyServlet extends HttpServlet {
public void init() throws ServletException {
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
}
catch (ClassNotFoundException e) {
System.out.println("Couldn't load OracleDriver");
throw new UnavailableException("Couldn't load OracleDriver");
}
}
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/plain");
PrintWriter out = res.getWriter();
HttpSession session = req.getSession(true);
Connection con;
synchronized (session) {
ConnectionHolder holder =
(ConnectionHolder) session.getAttribute("servletapp.connection");
if (holder == null) {
try {
holder = new ConnectionHolder(DriverManager.getConnection(
"jdbc:oracle:oci7:ordersdb", "user", "passwd"));
session.setAttribute("servletapp.connection", holder);
}
catch (SQLException e) {
log("Couldn't get db connection", e);
}
}
con = holder.getConnection();
}
try {
Statement stmt = con.createStatement();
stmt.executeUpdate("UPDATE INVENTORY SET STOCK = (STOCK - 10) ");
stmt.executeUpdate("UPDATE SHIPPING SET SHIPPED = (SHIPPED + 10) ");
res.sendRedirect(res.encodeRedirectURL(req.getContextPath() + "/servlet/CardHandler"));
}
catch (Exception e) {
try {
con.rollback();
session.removeAttribute("servletapp.connection");
}
catch (Exception ignored) { }
out.println("Order failed. Please contact technical support.");
}
}
}
<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<servlet><servlet-name>MyServletName</servlet-name>
<servlet-class>MyServlet</servlet-class>
</servlet>
<servlet-mapping><servlet-name>MyServletName</servlet-name>
<url-pattern>*.htm</url-pattern>
</servlet-mapping>
</web-app>
]]>