(Java) Async Task Chain

Demonstrates how to combine a sequence of asynchronous tasks into a single task chain to be run in a background thread.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // All Chilkat classes can be unlocked at once at the beginning of a program
    // by calling UnlockBundle.  It requires a Bundle unlock code.
    CkGlobal chilkatGlob = new CkGlobal();
    boolean success = chilkatGlob.UnlockBundle("Anything for 30-day trial.");
    if (success != true) {
        System.out.println(chilkatGlob.lastErrorText());
        return;
        }

    CkMailMan mailman = new CkMailMan();

    // Set the POP3 server's hostname
    mailman.put_MailHost("pop.someMailServer.com");

    // Set the POP3 login/password and any other requirements..
    mailman.put_PopUsername("myLogin");
    mailman.put_PopPassword("myPassword");
    mailman.put_PopSsl(true);
    mailman.put_MailPort(995);

    // Connect to the POP3 server:
    success = mailman.Pop3BeginSession();
    if (!success) {
        System.out.println(mailman.lastErrorText());
        return;
        }

    // Get the number of messages in the mailbox.
    int numMessages = mailman.GetMailboxCount();
    if (numMessages == 0) {
        System.out.println("No email messages in the POP3 mailbox.");
        return;
        }

    CkTaskChain taskChain = new CkTaskChain();

    // Create async task objects to fetch each email message
    // by its sequence number
    int i;
    CkTask task;

    for (i = 1; i <= numMessages; i++) {

        task = mailman.FetchByMsgnumAsync(i);
        if (mailman.get_LastMethodSuccess() == false) {
            System.out.println(mailman.lastErrorText());
            return;
            }

        // Append each task to the task chain.
        success = taskChain.Append(task);
        if (!success) {
            System.out.println(taskChain.lastErrorText());
            return;
            }

        }

    // At this point, no tasks have actually started running.
    // All we've done so far is to create tasks for the work that will be done
    // when the task chain is run.

    // Start the task chain running in a background thread.
    // Each task is run one after the other (on the same background thread) until all tasks have completed.
    // The task chain will stop at the first task that fails.
    taskChain.put_StopOnFailedTask(true);
    success = taskChain.Run();
    if (!success) {
        System.out.println(taskChain.lastErrorText());
        return;
        }

    // The application is now free to do anything else
    // while the emails are being downloaded

    // For this example, we'll simply sleep and periodically
    // check to see if the taskchain if finished. 
    while (taskChain.get_Finished() != true) {

        // Sleep 100 ms.
        taskChain.SleepMs(100);

        }

    // A finished task chain could be one that was canceled, aborted, or truly finished.  

    // If the task chain "completed", then it ran to completion.  A "completed" task will
    // have a StatusInt equal to 7.   If the task finished, but was not completed, then it must've
    // been aborted or canceled:
    if (taskChain.get_StatusInt() != 7) {
        System.out.println("Task did not complete.");
        System.out.println("task chain status: " + taskChain.status());
        return;
        }

    CkEmail email = new CkEmail();

    int numTasks = taskChain.get_NumTasks();
    int taskIdx = 0;

    while ((taskIdx < numTasks)) {

        task = taskChain.GetTask(taskIdx);

        // Load the email object with email downloaded by this task.
        success = email.LoadTaskResult(task);
        if (!success) {
            System.out.println("Failed to load email object for task.");
            }
        else {
            System.out.println(email.ck_from() + "; " + email.subject());
            }

        taskIdx = taskIdx+1;
        }
  }
}