Sending E-Mail from RPG, Take Two

October 27, 2004 Hey, David

The code for this article is available for download.

Is there a continuation article to “Sending E-Mail from RPG” from last May? It was a really good article, but I’m not sure I can make modifications to be able to send e-mail with attachments. My problem is in the RPG program. I don’t know how to declare the prototype for the DataSource object (attachments). Could you please help or refer me to an article I could read?

–Ana

Your question points out that I could have made the Mailer Java class more RPG friendly. Although it is possible to create a DataSource in RPG, it is much easier to put the code in the Mailer class.

To solve this problem, I used a feature of Java called method overloading. I left the SendMultiPartMail method intact, with its DataSource array parameter, and added a new SendMultiPartMail method that takes a String array containing file names in place of the DataSource array. So now there are two SendMultiPartMail methods, and the Java runtime environment will call the appropriate method based on the parameter types passed at runtime, which is the essence of overloading.

I added the new method because it is much easier to create a String array in RPG IV than to create an array of DataSource objects. The following code shows the new method, which creates a DataSource in Java code and calls the original method.

/**
 * Send a multipart email.
 * @param to        The destination address
 * @param from      The source address
 * @param subject   The subject line for the email
 * @param message   The message for the email
 * @param fileNames The names of files to attach
 * @throws MessagingException
 */
public static void sendMultiPartMail(
    String to,
    String from,
    String subject,
    String message,
    String[] fileNames)
    throws MessagingException {
    DataSource bodyParts[] = new DataSource[fileNames.length];

    for (int i = 0; i < fileNames.length 
         && filenames[i] != null; i++) {
        bodyParts[i] = new FileDataSource(new File(fileNames[i]));
    }
    sendMultiPartMail(to, from, subject, message, bodyParts);
 }
 

Calling this new method from your RPG IV program is now much easier. The following snippet shows the RPG IV prototype and call for this new Java method.

DMailer$sendMultiPartMail...
D                 PR                  STATIC
D                                     EXTPROC(
D                                       *JAVA:
D                                       'demo.Mailer':
D                                       'sendMultiPartMail')
D to                                  LIKE(newString)
D                                     CONST
D from                                LIKE(newString)
D                                     CONST
D subject                             LIKE(newString)
D                                     CONST
D message                             LIKE(newString)
D                                     CONST
D attachments                         LIKE(newString)
D                                     CONST
D                                     DIM(32767)
D                                     OPTIONS(*VARSIZE)
 …
Dto               S               O   CLASS(*JAVA:'java.lang.String')
Dfrom             S               O   CLASS(*JAVA:'java.lang.String')
Dsubject          S               O   CLASS(*JAVA:'java.lang.String')
Dmessage          S               O   CLASS(*JAVA:'java.lang.String')
Dattachments      S               O   CLASS(*JAVA:'java.lang.String')
D                                     DIM(10)
...
 /free
     to = newString('somebody@itjungle.com');
     from = newString('dmorris@itjungle.com');
     subject = newString('This is the subject');
     message = newString('Here is a test message');
     attachments(1) = newString('/java/mailer/demo/Mailer.java');
     Mailer$sendMultiPartMail(to: from: subject: message: attachments);
 /end-free

This example attaches a single file found in the IFS to an e-mail message and sends it. The RPG IV code in this example supports up to 10 attachments; however, you could change DIM(10) to support any number of attachments. Instructions for creating the Mailer Java program are contained in the source. You will also have to modify Mailer.properties to point to your mail server. If you send e-mail directly through an ISP, you may also need to supply a user and password.

Now change the e-mail addresses and attachment location in the mailerdemo RPG IV program and create it using CRTBNDRPG. Before you run mailerdemo, you need to add Mailer.class, along with Mailer.properties, Java Mail.jar, and Activation.jar, to your classpath. You would do this with the ADDENVVAR command, changing the path to reflect your environment, like this.

ADDENVVAR VAR('/java/mailer:/java/javamail-1.3.1/
   mail.jar:/java/jaf-1.0.2/activation.jar')

Now run the example. If everything is set up properly, you should find an e-mail in your inbox with the source for the Mailer Java program attached.

–David Morris

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