Java Database Connectivity (JDBC)

Salam 2all
please help me to solve this problem
i have this error
Invalid column name: get_column_index
when i execute this code
rs = stmt.executeQuery("Select EmpNo,Name,Degree,Occupation,DomainNo,Signature from Employee where EmpNo='"+cno+"'");
if (rs.next())
{
emp.setText(rs.getString("EmpNo"));
name.setText(rs.getString("Name"));
degree.setText(rs.getString("Degree"));
occ.setText(rs.getString("Occupation"));
int index=SearchIndex(Integer.parseInt(rs.getString("DomainNo"))); dom.setSelectedIndex(index);
domn.setText(rs.getString("Signature"));
}
//////////////////////////////////////////
By tracing the code using System.out.println("BBBBBBBB");
i reach that the error is in the statment
{ domn.setText(rs.getString("Signature"));
}
but the spelling for"Signature" is the same, and i write it in the oracle creation table as follow
create table Employee(
EmpNo varchar(40) NOT NULL,
Name varchar(40) NOT NULL,
Degree varchar(4),
Occupation varchar(4),
DomainNo varchar(4),
Signature varchar(40),
primary key(EmpNo ),
foreign key(DomainNo) references Cycle);
///////////////////////////////////////////

Thanks 4 ur help
Salam 2all