/* * Copyright (c) 2000 David Flanagan. All rights reserved. * This code is from the book Java Examples in a Nutshell, 2nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book (recommended), * visit http://www.davidflanagan.com/javaexamples2. */ package com.davidflanagan.examples.servlet; import javax.servlet.*; import javax.servlet.http.*; import java.sql.*; import java.io.*; /** * This class demonstrates how JDBC can be used within a servlet. It uses * initialization parameters (which come from the web.xml configuration file) * to create a single JDBC database connection, which is shared by all clients * of the servlet. ***/ public class Query extends HttpServlet { Connection db; // This is the shared JDBC database connection public void init() throws ServletException { // Read initialization parameters from the web.xml file ServletConfig config = getServletConfig(); String driverClassName = config.getInitParameter("driverClassName"); String url = config.getInitParameter("url"); String username = config.getInitParameter("username"); String password = config.getInitParameter("password"); // Use those init params to establish a connection to the database // If anything goes wrong, log it, wrap the exception and re-throw it try { Class.forName(driverClassName); db = DriverManager.getConnection(url, username, password); } catch (Exception e) { log("Can't create DB connection", e); throw new ServletException("Query: can't initialize: " + e.getMessage(), e); } } /** Close the database connection when the servlet is unloaded */ public void destroy() { try { db.close(); } // Try to close the connection catch (SQLException e) {} // Ignore errors; at least we tried! } public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/html"); // We're outputting HTML PrintWriter out = response.getWriter(); // Where to output it to // Output document header and a form for entering SQL queries // When the form is submitted, this servlet is reloaded out.println("
" + metadata.getColumnLabel(i+1) + " | "); out.println("
---|
" + results.getObject(i+1) + " | "); out.println("