Question

I have a general question regarding mysql queries and java. Can you take a value that has been entered into a textbox by a user then assign that to a String, then in a whole separate class capture that String to fulfill the parameter in a mysql query. The mysql query would run and if the parameter is equal to the data in the table it will return a message of successful login etc. So I am asking for a yes or no style answer on this…any extra input would be helpful but not required. I know you can pass values from one class to another but in this instance I do wonder if it is possible in the running of a mysql query.

Answer 1

Of course it’s possible. How would we implement applications using a database if it weren’t:

In GUI:

String login = loginField.getText();
boolean exists = userDao.checkUserExistence(login);

...

In UserDAO:

public boolean checkUserExistence(String login) {
    String sql = "select u.id from user u where u.login = ?";
    PreparedStatement stmt = connection.prepareStatement(sql);
    stmt.setString(1, login);
    ResultSet rs = stmt.executeQuery();
    return rs.next();
}

Note that the above is only pseudo-code. It doesn’t handle exceptions and doesn’t close resources properly. It’s just to give you an idea.

Learn about prepared statements.