Hi
I have been trying to make a Connection Pool with the example of the book: Core
Servlets and Java Server Pages of Marty Hall, which is stored in
www.coreservlets.com. The example is the Listing 18.20
ConnectionPoolServlet.java in page 510. My problem is that when I try to compile
the servlet there are like 8 errors related to: cannot resolve symbol. Any help?
This is the code:
package coreservlets;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
/** A servlet that reads information from a database and
* presents it in an HTML table. It uses connection
* pooling to optimize the database retrieval. A good
* test case is ConnectionPool.html, which loads many
* copies of this servlet into different frame cells.
*/
public class ConnectionPoolServlet extends HttpServlet {
private ConnectionPool connectionPool;
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
String table;
try {
String query =
"SELECT firstname, lastname " +
" FROM employees WHERE salary > 70000";
Connection connection = connectionPool.getConnection();
DBResults results =
DatabaseUtilities.getQueryResults(connection,
query, false);
connectionPool.free(connection);
table = results.toHTMLTable("#FFAD00");
} catch(Exception e) {
table = "Error: " + e;
}
response.setContentType("text/html");
// Prevent the browser from caching the response. See
// Section 7.2 of Core Servlets and JSP for details.
response.setHeader("Pragma", "no-cache"); // HTTP 1.0
response.setHeader("Cache-Control", "no-cache"); // HTTP 1.1
PrintWriter out = response.getWriter();
String title = "Connection Pool Test";
out.println(ServletUtilities.headWithTitle(title) +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<CENTER>\n" +
table + "\n" +
"</CENTER>\n</BODY></HTML>");
}
/** Initialize the connection pool when servlet is
* initialized. To avoid a delay on first access, load
* the servlet ahead of time yourself or have the
* server automatically load it after reboot.
*/
public void init() {
int vendor = DriverUtilities.SYBASE;
String driver = DriverUtilities.getDriver(vendor);
String host = "dbhost2.apl.jhu.edu";
String dbName = "605741";
String url = DriverUtilities.makeURL(host, dbName, vendor);
String username = "hall";
String password = "xxxx"; // Changed :-)
try {
connectionPool =
new ConnectionPool(driver, url, username, password,
initialConnections(),
maxConnections(),
true);
} catch(SQLException sqle) {
System.err.println("Error making pool: " + sqle);
getServletContext().log("Error making pool: " + sqle);
connectionPool = null;
}
}
public void destroy() {
connectionPool.closeAllConnections();
}
/** Override this in subclass to change number of initial
* connections.
*/
protected int initialConnections() {
return(10);
}
/** Override this in subclass to change maximum number of
* connections.
*/
protected int maxConnections() {
return(50);
}
}
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