Java Coding Problems

267. Uploading with multipart

As we saw in the Setting a request body section, we can send a file (text or binary) to the server via BodyPublishers.ofFile() and a POST request.

But sending a classical upload request may involve a multipart form POST with Content-Type as multipart/form-data.

In this case, the request body is made of parts that are delimited by a boundary, as shown in the following illustration (--779d334bbfa... is the boundary):

However, JDK 11's HTTP Client API doesn't provide built-in support for building this kind of request body. Nevertheless, by following the preceding screenshot, we can define a custom BodyPublisher