import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.javaexchange.dbConnectionBroker.*;
/* This example has been adapted from the GlobalBrokerExample1.java file
available from www.javaexchange.com. It has been modified to work
specifically with MySQL and Servlets.Net web hosting services.
The example shows how to set up a global Database Connection Broker in
a Servlet using JDBCGlobalBroker and DbConnectionBroker. Once
a JDBCGlobalBroker has been created, the settings that it was created
with will be used for all additional instances of the class. This
allows all of your servlets to use the same pool of database connections.
For example, if you had 10 servlets and a 2 database connections to your
database, you will want to set up a global broker with a max pool size
of 2. That way, all 10 servlets would share the 2 connections in
round-robin order.
You could alternatively have each servlet manage its own pool of database
connections. This can be done by creating an instance of
JDBCConnectionBroker rather than JDBCGlobalBroker. The drawback is that
each servlet will then need its own set of database connections,
potentially using more connections than your Servlets.Net account allows.
Servlets.Net encourages you to use the JDBCGlobablBroker and share a
pool of all of your connections with all of your servlets. This sample
demonstrates how to do this.
Whenever you change a servlet or a JSP page on your site, Live Software's
JRun servlet runner will reload all of your servlets. When this happens,
your broker will be destroyed and a new one created. This might cause
problems. To avoid this, you should set up a "master broker servlet"
that extends the PermanentServlet class:
com.livesoftware.jrun.PermanentServlet
Servlets implementing this interface will have their "init" and "destroy"
methods called when first loaded, and when the servlet engine shuts down.
Usually, these type of servlets should not be dynamically reloaded. This
means that these servlets should be placed within your "classes" directory
rather than within your "servlets" directory.
- Servlets.Net Support Staff
*/
public class MySQLBrokerExample extends HttpServlet {
Connection conn = null;
JDBCGlobalBroker myGlobalBroker; // A global (all Servlets) connection pool
public void destroy() {
super.destroy();
myGlobalBroker.destroy();
}
public void doGet (HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
res.setContentType("text/html");
ServletOutputStream out = res.getOutputStream();
out.println("");
out.println("MySQLBrokerExample");
out.println("");
conn = myGlobalBroker.getConnection(); // Connection from the Global Pool
Statement stmt=null;
try {
// Create a Statement.
stmt = conn.createStatement();
// Set up the Result Set
ResultSet rset = stmt.executeQuery ("select name from tablename");
// Print out the results
while (rset.next())
out.println ("The query responded with: " + rset.getString(1) + "
");
}
catch (SQLException e2) {
out.println("SQL exception." + e2.getMessage());
e2.printStackTrace();
}
finally {
try{if(stmt != null) {stmt.close();}} catch(SQLException e1){};
myGlobalBroker.freeConnection(conn); // Release connection back to pool
}
out.println("");
}
public void init (ServletConfig config) throws ServletException {
super.init(config);
try {
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
try {
// Create the database connection broker
myGlobalBroker = new JDBCGlobalBroker("org.gjt.mm.mysql.Driver",
"jdbc:mysql://www.yourdomain.com/your_database_name",
"username", "password", 1, 2, "/home/username/logs/dbcb.log", 1.0);
}
catch (IOException e) {
System.out.println("Problem creating JDBCGlobalBroker:" + e.getMessage());
e.printStackTrace();
}
catch (NumberFormatException en) {
System.out.println("Number formatted incorrectly");
en.printStackTrace();
}
}
catch (ClassNotFoundException e1) {
System.out.println("Class not found");
e1.printStackTrace();
}
catch (InstantiationException e2) {
System.out.println("Instantiation problem");
e2.printStackTrace();
}
catch (IllegalAccessException e3) {
System.out.println("Illegal Access problem");
e3.printStackTrace();
}
}
}