Retrieving binary file from post request

Question

Sending a POST request (Apache httpclient, here Kotlin source code):

val httpPost = HttpPost("http://localhost:8000")
val builder = MultipartEntityBuilder.create()
builder.addBinaryBody("file", File("testFile.zip"),
        ContentType.APPLICATION_OCTET_STREAM, "file.ext")
val multipart = builder.build()
httpPost.entity = multipart
val r = httpClient.execute(httpPost)
r.close()

I receive the request in my post handler as a via spark-java Request-object. How do I retrieve the original file (plus the file name as a bonus) from the post request? The request.bodyAsBytes() method seems to add some bytes because the body is larger than the original file.

Thanks, Jörg

Answer 1

Near the bottom of Spark's Documentation page there is a section "Examples and FAQ". The first example is "How do I upload something?". From there, it links further to an example on GitHub.

In short:

post("/yourUploadPath", (request, response) -> {
    request.attribute("org.eclipse.jetty.multipartConfig", new MultipartConfigElement("/temp"));
    try (InputStream is = request.raw().getPart("file").getInputStream()) {
        // Use the input stream to create a file
    }
    return "File uploaded";
});

To access the original file name:

request.raw().getPart("file").getSubmittedFileName()

To handle multiple files or parts, I usually have code similar to the following (assuming only files are included in the multi-part encoded upload):

for (Part part : req.raw().getParts()) {
  try (InputStream stream = part.getInputStream()) {
    String filename = part.getSubmittedFileName();
    // save the input stream to the filesystem, and the filename to a database
  }
}