Java 9 HttpClient send a multipart/form-data request

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Answer 1

I recently released a library providing useful extensions to Java 11's HttpClient. The library contains a MultipartBodyPublisher with a convenient and easy to use MultipartBodyPublisher.Builder. Here is an example using it (JDK11 or later is required):

MultipartBodyPublisher multipartBody = MultipartBodyPublisher.newBuilder()
    .textPart("foo", "foo_text")
    .filePart("bar", Path.of("path/to/file.txt"))
    .formPart("baz", BodyPublishers.ofInputStream(() -> ...))
    .build();
HttpRequest request = HttpRequest.newBuilder()
    .uri(URI.create("https://example.com/"))
    .POST(multipartBody)
    .build();

Note that you can also add any BodyPublisher (or HttpHeaders) you want. See the user guide for more details.