Using JButtons to execute SQL queries with JDBC

Question

I'm writing a simple JAVA GUI to read an SQL query from a JTextFrame and execute it.

The connect and execute buttons are both JButtons, but the compiler won't compile my code because I can't append a "throws SQLException" to actionPerformed in my Listener private classes. I tried writing separate methods, but the same problem still persists. Here's an example:

public void connect() throws SQLException {
    conxn = DriverManager.getConnection(URL, Username, Password);
}
private class SelectBut implements ActionListener {  
    public void actionPerformed(ActionEvent event){
        connect();
    }
}

The compiler just throws this back at me:

TextFrame.java:123: unreported exception java.sql.SQLException; must be caught or declared to be thrown  
public void actionPerformed(ActionEvent event){connect();}}

Any suggestions?

Catch it or declare it to be thrown, just as the error message tells you to. You’ll realize that you can not declare it to be thrown so I guess you have to catch it. Wow, that was hard. — Bombe
– Bombe, Commented Nov 24, 2009 at 11:49

Nettogrof · Accepted Answer · 2009-11-24 01:59:14Z

3

Since SQLException are checked exception , you must re-throw or catch it.

in your case your actionPerformed method can be something like that :

public void actionPerformed(ActionEvent event){
    try{
         connect();
    }catch(SQLException e){
         e.printStackTrace();
     }
 }

Here a tutorial about Catching and Handling Exception

answered Nov 24, 2009 at 1:59

Nettogrof

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3 Comments

Vincent B. Over a year ago

Yep, any method that may throw an execption must be within a try/catch block or the method calling this method must re-throw it.

duffymo Over a year ago

Since the actionPerformed method doesn't include a throws clause, you can't throw any checked exceptions in your implementation. You'll have to catch it.

Kevin Day Over a year ago

For what it's worth, the exception shouldn't be silently absorbed like this (or converted to a runtime exception) - this is a call that's going to occur on the EDT, and bringing the EDT down isn't a good idea. At minimum, display a JOptionPane dialog box with the error message. Another point to make here: The database query will almost certainly be a long running task - running that on the EDT is a bad idea. I suggest that you do a bit more reading up on developing Swing apps (SwingWorker may be a good idea here)

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