ResultSet.getString(1) throws java.sql.SQLException: Invalid operation at current cursor position

Question

When I run the following servlet: ``` // package projectcodes; public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { String UserID = request.getParameter("UserID"); String UserPassword = request.getParameter("UserPassword"); String userName = null; String Email = null; Encrypter encrypter = new Encrypter(); String hashedPassword = null; try { hashedPassword = encrypter.hashPassword(UserPassword); Context context = new InitialContext(); DataSource ds = (DataSource)context.lookup("java:comp/env/jdbc/photog"); Connection connection = ds.getConnection(); String sqlStatement = "SELECT email,firstname FROM registrationinformation WHERE password='" + hashedPassword + "'"; PreparedStatement statement = connection.prepareStatement(sqlStatement); ResultSet set = statement.executeQuery(); userName = set.getString(1); // <<---------- Line number 28 response.sendRedirect("portfolio_one.jsp"); // userName = set.getString("FirstName"); Emai…

Accepted Answer

You should use the `next` statement first.

```
ResultSet set = statement.executeQuery();
if (set.next()) {
    userName = set.getString(1);
    //your logic...
}
```

UPDATE

As the Java 6 Documentation says

A ResultSet cursor is initially positioned before the first row; the first call to the method next makes the first row the current row; the second call makes the second row the current row, and so on.

This means when you execute the sentence

```
ResultSet set = statement.executeQuery();
```

The ResultSet `set` will be created and pointing to a row before the first result of the data. You can look it this way:

SELECT email,firstname FROM registrationinformation

```
    email              | firstname
    ____________________________________
0                                        <= set points to here
1   email1@gmail.com   | Email1 Person
2   foo@bar.com        | Foo Bar
```

So, after openning your ResulSet, you execute the method `next` to move it to the first row.

```
if(set.next()) 
```

Now `set` looks like this.

```
    email              | firstname
    ____________________________________
0
1   email1@gmail.com   | Email1 Person   <= set points to here
2   foo@bar.com        | Foo Bar
```

If you need to read all the data in the ResultSet, you should use a while instead of if:

```
while(set.next()) {
    //read data from the actual row
    //automatically will try to forward 1 row
}
```

If the `set.next()` return false, it means that there was no row to read, so your while loop will end.

More information here.

ResultSet.getString(1) throws java.sql.SQLException: Invalid operation at current cursor position

Solution

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