Troubleshooting email sending with inline images using Jersey 2 and Mailgun API

Other Questions Mailgun
1

I’m having trouble sending emails with inline images using Jersey 2 and the Mailgun API. My code is based on Mailgun’s docs, but I’m getting an error about a missing MessageBodyWriter.

Here’s what I’ve done:

  1. Set up a Jersey 2 client with the MultiPartFeature registered.
  2. Created a FormDataMultiPart to structure my email content.
  3. Added an inline image using a FileDataBodyPart.

When I send the request, I receive the following error:

MessageBodyWriter not found for media type=multipart/form-data, type=class com.sun.jersey.multipart.FormDataMultiPart

I’ve reviewed my dependencies and confirmed that jersey-media-multipart is included. What could be causing this issue, and how can I resolve it to successfully send emails with inline images?

Here’s a simplified snippet of my updated code:

Client client = ClientBuilder.newBuilder().register(MultiPartFeature.class).build();
WebTarget target = client.target("https://api.mailgun.net/v2/example.com/messages");

FormDataMultiPart form = new FormDataMultiPart();
form.field("to", "[email protected]");
form.field("html", "<img src=\"cid:image.jpg\">");
form.bodyPart(new FileDataBodyPart("inline", new File("image.jpg")));

Response response = target.request().post(Entity.entity(form, MediaType.MULTIPART_FORM_DATA_TYPE));

Any insights on what might be wrong?

2

I encountered a similar issue when working with Jersey 2 and Mailgun. The problem lies in how Jersey handles multipart form data. Here’s what worked for me:

First, make sure you’re using the correct Jersey version (2.x) and that all your dependencies are compatible. Then, try explicitly registering the MultiPartFeature with your client:

Client client = ClientBuilder.newClient(new ClientConfig().register(MultiPartFeature.class));

Also, when creating the Entity, specify the media type more precisely:

Entity.entity(form, new MediaType("multipart", "form-data"))

These changes resolved the MessageBodyWriter error for me. If you’re still having issues, double-check that you’re not mixing Jersey 1.x and 2.x dependencies, as that can cause conflicts.

Lastly, ensure you’re using the correct Mailgun API endpoint. The one in your code looks outdated. The current base URL should be ‘https://api.mailgun.net/v3’.

3

I’ve dealt with this exact issue before. The problem is likely due to how Jersey 2 handles multipart form data. Here’s what solved it for me:

  1. Double-check your Jersey version. Make sure it’s 2.x and all dependencies match.

  2. Try using the MultivaluedHashMap instead of FormDataMultiPart. It worked better in my experience:

MultivaluedMap<String, String> formData = new MultivaluedHashMap<>();
formData.add("to", "[email protected]");
formData.add("html", "<img src=\"cid:image.jpg\">");

Entity<?> entity = Entity.entity(formData, MediaType.APPLICATION_FORM_URLENCODED);
  1. For the inline image, use a separate request part:
MultiPart multiPart = new MultiPart(MediaType.MULTIPART_FORM_DATA_TYPE);
multiPart.bodyPart(new FormDataBodyPart(FormDataContentDisposition.name("inline").fileName("image.jpg").build(), new File("image.jpg"), MediaType.APPLICATION_OCTET_STREAM_TYPE));

Combine these approaches, and it should resolve your MessageBodyWriter issue. Let me know if you need more help!

4

hey, i had this problem too. try using the jersey-media-multipart module version 2.35 or later. also, make sure ur not accidentally using any old jersey 1.x stuff in ur project. that can mess things up. check ur pom.xml or build.gradle file to be sure all the versions match up. good luck!