Paypal payment processing callback on JSC application

Question

I have implemented a Paypal payment processig application with JSC, in which the Paypal server will call my Servlet, upon successful completion of the payment.
The algorithem on the Servlet is something similar to the following:
if (condition_one){
database operation_1;
database operation_2;
But the problem is, when "condition_1" is met, I have the following cases:
(1) Sometimes, neither "database operation_1" nor "database operatio_2" is performed
(2) Sometimes, either "database operation_1" or "database operatio_2" is only performed
(3) Sometimes, both "database operation_1" and "database operatio_2"are performed
By theory, only the 3rd case must occur all the time, but I do not understand why the first two cases occur sometimes? Am I missing anything?
Thank you.

Answer 1

Here is the part of the code:
if (paymentStatus.equals("Completed")){
System.out.println("\"Completed\" is returned by Paypal");
    if(isSubscription){
System.out.println("Inside the if loop");
    updatePayment(query_1); //This is "database operation_1"
    updatePayment(query_2); //This is "database operation_2"
In the above code query_1 and query_2 are acting on the same database (on a same computer) but on two different tables.
The updatePayment(String query) method as follows:
private void updatePayment(String query){
        Statement sta=null;
        Connection con=null;
       // ResultSet rs=null;
        try {
System.out.println(" SUCCESS!! (servlet/Payment.java/UpdateDatabase()/ Entered into Try block successfully");          
//Class.forName("com.mysql.jdbc.Driver")
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            Context initContext = new InitialContext();
            DataSource ds = (DataSource)initContext.lookup("jdbc/MySQLDataSource");
            Connection conn = ds.getConnection();
            sta = conn.createStatement();
            sta.executeUpdate(query);
           // rs.close();
            sta.close();
            conn.close();
        System.out.println(" SUCCESS!! (servlet/Payment.java/UpdateDatabase()/ Try block executed successfully");
        } catch (Exception e) {
            System.out.println(" ERROR!! (servlet/Payment.java/UpdateDatabase()/catch blok) "+e.getMessage());
            // e.printStackTrace();
    }Edited by: MISS_DUKE on Feb 12, 2008 12:40 PM