Java

Get the Content-ID of an Attachment

Demonstrates the Chilkat Email.GetAttachmentContentID method, which returns the Content-ID header field for the Nth attachment. The index is zero-based, so the first attachment is 0. This example adds an attachment and reads its Content-ID (which may be empty when none was assigned).

Background: A Content-ID is a unique identifier for a MIME part. It is essential for inline "related" resources, where HTML references an image by cid:, but ordinary file attachments usually have none. Reading it is useful when inspecting how a message is assembled, or when distinguishing parts that are referenced from the body versus those meant purely as downloadable attachments.

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Java

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[])
  {
    //  Demonstrates the GetAttachmentContentID method, which returns the Content-ID header
    //  field for the Nth attachment.  The index is zero-based (the first attachment is 0).

    CkEmail email = new CkEmail();
    email.put_Subject("Attachment Content-ID");

    email.AddStringAttachment("notes.txt","Some notes.");

    //  Get the Content-ID of the first attachment (may be empty if none was assigned).
    String cid = email.getAttachmentContentID(0);
    System.out.println("Attachment 0 Content-ID: " + cid);
  }
}