statement.setFloat(1, newSalaries[i]);

statement.setInt(2, employeeIDs[i]);

statement.execute();

}

The performance advantages of prepared statements can vary significantly,

depending on how well the server supports precompiled queries and how effi 

ciently the driver handles raw queries. For example, Listing 18.18 presents a

class that sends 40 different queries to a database using prepared statements,

then repeats the same 40 queries using regular statements. With a PC and a

28.8K modem connection to the Internet to talk to an Oracle database, pre 

pared statements took only half the time of raw queries, averaging 17.5 seconds

for the 40 queries as compared with an average of 35 seconds for the raw que 

ries. Using a fast LAN connection to the same Oracle database, prepared state 

ments took only about 70 percent of the time required by raw queries,

averaging 0.22 seconds for the 40 queries as compared with an average of 0.31

seconds for the regular statements. With Sybase, prepared statement times

were virtually identical to times for raw queries both with the modem connec 

tion and with the fast LAN connection. To get performance numbers for your

setup, download 

DriverUtilities

.java from 

http://www.coreserv 

lets.com/

, add information about your drivers to it, then run the 

Prepared 

Statements

 program yourself. 

Listing 18.18 PreparedStatements.java 

package coreservlets;

import java.sql.*;

/** An example to test the timing differences resulting

 *  from repeated raw queries vs. repeated calls to

 *  prepared statements. These results will vary dramatically

 *  among database servers and drivers. 

*/

public class PreparedStatements {

  public static void main(String[] args) {

    if (args.length < 5) {

      printUsage();

      return;

    }

    String vendorName = args[4];

    int vendor = DriverUtilities.getVendor(vendorName);

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

Servlet and JSP training courses by book's author: courses.coreservlets.com.