java code for Database transaction

import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;

public class DbServletTrans extends HttpServlet {

DataSource pool;

public void init() throws ServletException {

Context env = null;

try {

env = (Context) new InitialContext().lookup("java:comp/env");
pool = (DataSource) env.lookup("jdbc/oracle-8i-athletes");
if (pool == null)
throw new ServletException(
"'oracle-8i-athletes' is an unknown DataSource");

} catch (NamingException ne) {

throw new ServletException(ne);

}

}

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {

Connection conn = null;
Statement stmt = null;

response.setContentType("text/html");
java.io.PrintWriter out = response.getWriter();
out
.println("");
out.println("

These SQL statements are part of a transaction

");
out.println("CallableStatement.executeUpdate()");
out.println("

");
out.println("Statement.executeUpdate()");
out.println("

");

try {

conn = pool.getConnection();

out.println("AutoCommit before setAutoCommit(): "
+ conn.getAutoCommit() + "

");

out.println("Transaction isolation level: ");

switch (conn.getTransactionIsolation()) {

case 0:
out.println("TRANSACTION_NONE

");
break;
case 1:
out.println("TRANSACTION_READ_UNCOMMITTED

");
break;
case 2:
out.println("TRANSACTION_READ_COMMITTED

");
break;
case 4:
out.println("TRANSACTION_REPEATABLE_READ

");
break;
case 8:
out.println("TRANSACTION_SERIALIZABLE

");
break;
default:
out.println("UNKNOWN

");

}
conn.setAutoCommit(false);

CallableStatement cs = null;

//Create an instance of the CallableStatement
cs = conn.prepareCall("{call addEvent (?,?,?)}");

cs.setString(1, "Salisbury Beach 5-Miler");
cs.setString(2, "Salisbury MA");
cs.setString(3, "14-Aug-2003");

//Call the inherited PreparedStatement.executeUpdate() method
cs.executeUpdate();

String sql = "update raceevent set racedate='13-Aug-2003' "
+ "where name='Salisbury Beach 5-Miler'";

int res = 0;

stmt = conn.createStatement();

res = stmt.executeUpdate(sql);

//commit the two SQL statements
conn.commit();

} catch (Exception e) {

try {
//rollback the transaction in case of a problem
conn.rollback();

} catch (SQLException sqle) {
}

throw new ServletException(e.getMessage());

} finally {

try {

if (stmt != null)
stmt.close();

if (conn != null)
conn.close();//this returns the Connection to the
// Connection pool

} catch (SQLException sqle) {
}

}
out.println("");
out.close();

} //doGet

}