Re: What's wrong in this transaction?

Thanks vahan...
but it doesn't work!!!
I've the same error!
Now i've used,following you
package giu;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.http.HttpSession;
import javax.sql.DataSource;

public class QueryManager extends BaseBean{
    private int key;

    public QueryManager(){}

public String executeTransaction() throws java.sql.SQLException {
    java.sql.Connection conn = null;
    javax.sql.DataSource dataSource =
Singleton.getInstance().getDataSource();
    conn = dataSource.getConnection();

    Experiment exp = (Experiment) ViewUtils.eval("#{experiment}");

    List results = new ArrayList();
    ResultSet rs = null;
    Statement stmt = null;
    boolean allgood = false;
    if (conn != null) {

        conn.setAutoCommit(false);
        //you can change Transaction Isolation level

//conn.setTransactionIsolation(java.sql.Connection.TRANSACTION_READ_COMMITT=
=ADED);

        conn.setSavepoint();//set rollback point

        try {
            for (int i = 0; i < exp.getExperiments().size(); i++) {

                ((java.sql.PreparedStatement)
                 exp.getExperiments().get(i)).executeUpdate();
                if (i == (exp.getExperiments().size() - 1)) {
                    conn.commit();
                }

            }
        } catch (Exception e) {
                conn.rollback();
                e.printStackTrace();
            }

    } else {
        System.out.println("connessione non disponibile");
    }

    return "submit";
}

}

but never,when sql exception comes rollback doesn't act!
Please help me..should i do other things for support transactions?
I'm using
mysql-connector-java-3.1.13.zip

and innodb table with mysql...what can i do?
Please help me