用JAVA连接ORACLE数据库查询不到数据

程序源代码如下：
package conn;

import java.sql.Connection;
import java.sql.Driver;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

public class CConnOracle {
/**
* @param args
*/
public static void main(String[] args) {
try {
int iStuId = 0;
String sStuName = null;
String sStuClass = null;
String strSql = "select col_stu_id, col_stu_name, col_stu_class from table_student";
Connection objConn = null;

Driver objDriver = (Driver)Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();

Properties objProp = new Properties();
objProp.put("user", "tester");
objProp.put("password", "tester");

objConn = objDriver.connect("jdbc:oracle:thin:@127.0.0.1:1521:testdb", objProp);
objConn.setAutoCommit(false);

PreparedStatement objStmt = objConn.prepareStatement(strSql,
ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);

ResultSet objRS = objStmt.executeQuery();
while(objRS.next())
{
iStuId = objRS.getInt("col_stu_id");
sStuName = objRS.getString("col_stu_name");
sStuClass = objRS.getString("col_stu_class");
Syste