Transaction - a few SQL-Expressions

Question

How can I execute a few SQL-Expressions.
Only the first SQL-Expression was executed. When i want to execute more SQL-Expressions then I get an Exception.
OK here is my code:
I hope its not too much.
The Connect class is at the end.
//add col at postgres 7.2 i need to use this version
public int addCol(String tabname,String tNewArea,String tNewDTyp,
String tNewLo,String tNewHi,String tNewNull,
String tNewPK){
try {
//Connect class with DriverManager or is DataSource better,
//but I need to use host,post,dbname,user,pw
con = Connect.openConnection(host,_port,_dbname,_user,_pw);
//is this a good way to do this with setAutoCommit
_con.setAutoCommit(false);
String sql="ALTER TABLE "+tabname+" ADD COLUMN "+tNewArea+" "+tNewDTyp+check;
stmt=con.prepareStatement(sql);
int res=_stmt.executeUpdate();
//pk exists ?
String pk=getPrimary(tabname);
//pk del
if(tNewPK.equals("Ja")){
if(pk!=null){
if(!pk.equals("")){
sql="DROP INDEX "+tabname+"_pkey";
stmt=con.prepareStatement(sql);
System.out.println(_stmt);
res = _stmt.executeUpdate();
System.out.println("col:"+res);
//pk add
sql="ALTER TABLE "+tabname+" ADD PRIMARY KEY("+tNewArea+")";
stmt=con.prepareStatement(sql);
System.out.println(_stmt);
res =_stmt.executeUpdate();
System.out.println("pk:"+res);
Connect.closeConnection(_con,_stmt,_rs);
_con.commit();
return 1;
catch(Exception e) {
try{
_con.rollback();
System.out.println("Transaktion at addCol failed");
catch(SQLException sql){
System.out.println("Exception at addCol: "+sql.getMessage());
finally {
Connect.closeConnection(_con,_stmt,_rs);
return -1;
public class Connect
//open connection
public static Connection openConnection(String host,String port,String db,String user,String pw)
Connection con = null;
try{
// Class.forName(driver);
con = DriverManager.getConnection("jdbc:postgresql://"+host+":"+port+"/"+db,user,pw);
return con;
catch (SQLException e) {
System.out.println("Exception in openConnection: "+e.getMessage());
catch (Exception exc){
return con;
//close connection
public static void closeConnection (Connection con, PreparedStatement stmt, ResultSet rs) {
if (rs != null) {
try {
rs.close();
catch (SQLException e) {}
if (stmt != null) {
try {
stmt.close();
catch (SQLException e) {}
if (con != null) {
try {
con.close();
catch (SQLException e) {}
Many thanks in advance
Olaf

Answer 1

Did you check wat kind of exception you are getting? May be the first sql statement itself is generating some db error which results in an exception being thrown.