Working with DML to Develop SQL Server based Java Applications using NetBeans IDE

In the previous sections, I explained how to retrieve information using the SELECT statement and writing the same to a text file.  Now, we shall discuss issuing DML statements such as INSERT, UPDATE and DELETE.

Let us work with a new form in the same application.  Within the "Projects" view, open "Source Packages," right-click on "MyDBPack," and go to "new->JFrame form" (Fig03).

Fig 3

I currently named it "DBSample04;" make sure that you change the code behind it to the following:

public DBSample04() {
        initComponents();
        this.setSize(300,200);
    }

You design the form exactly as in previous sections and copy the following code in the "Button click" event (or "ActionPerformed" event):

private void btnConnectActionPerformed(java.awt.event.ActionEvent
evt) {                                        

// TODO add your handling code here:
        try {
           Class.forName
("com.microsoft.jdbc.sqlserver.SQLServerDriver");          
            Connection conn = DriverManager.getConnection
("jdbc:microsoft:sqlserver://serverjag:1433","sa","");
            Statement sql_stmt = conn.createStatement();
            sql_stmt.executeUpdate("UPDATE Northwind..emp SET sal
= sal - 500");
            sql_stmt.close();
            conn.close();
            this.txtMsg.setText("updated successfully");
        }
        catch(Exception e) {
            this.txtMsg.setText("Failed to connect; Please view
Stack Trace");
            e.printStackTrace();
        }
    }  

In the above code, instead of using "executeQuery," I used "executeUpdate."  The "executeQuery" returns a "ResultSet" object, and we need to extract information from that.  The UPDATE statement does not return any "ResultSet." 

Even though I demonstrated a simple UPDATE in the above example, you can replace the same with other DML statements such as INSERT, DELETE and so on.

Before executing the application, you need to specify that the "DBSample04" is the form to get executed first.  Otherwise, you will see "DBSample03" every time.  This is a bit different from our other applications (in my previous series).

To specify your own form as the "start-up" form using NetBeans IDE:

· Right-click on the project ("SampleJavaApp1") and go to "properties." 

· Select "Run" in the "categories" and specify "MyDBPack.DBSample04" as the "Main Class" (Fig04)

Fig 4

· Finally click "OK."

Press F5 to execute and you should be able to see our new form.

Remarks

The entire code for this article is freely available in the form of a zip file.  That downloadable solution was developed using NetBeans 4.1 IDE and tested with Microsoft SQL Server 2000 database Enterprise Edition (with Service Pack 3).  I didn't really test it in any other version.  If you are unable to connect to the respective database, please post in the discussion section, so that I may guide you.

I used Microsoft Windows 2003 Standard Edition to work with this sample.  I request that you follow the steps according to the operating system installed on your computer. Most of them will be very similar to follow and very easy to understand (unless it is a different platform).

The final issue you need to know is that none of my articles in this series are optimized for performance.  Tuning/improving the performance of a Java application is beyond the scope of this article.  I simply wanted to explain the concepts clearly. 

Any doubts, bugs, errors, suggestions, feedback etc. are highly appreciated at jag_chat@yahoo.com.