This week's giveaway is in the Java/Jakarta EE forum. We're giving away four copies of Java EE 8 High Performance and have Romain Manni-Bucau on-line! See I think that the HTTP adapter will transfer the request to the container only after receiving the entire request, i.e. the servlet will be called only after the file is transferred to the server from client. Is it right?
If its right then there is no easy way to terminate the multipart request unless the entire file is transferred to the server. Is this right?
I'm not sure what you mean by an "http adapter". A server such as Tomcat receives all incoming traffic the same, but routes it to different subsystems and applications, depending on the URL. What you're referring to as the "http adapter" sounds a lot like the Default Servlet, which is where stuff goes if the appserver cannot determine any more suitable place to send it.
A MIME Multipart POST request consists of a single data stream posted to one of the application server's HTTP or HTTPS receiving ports. There are no "files" as such. When you "submit a file" what you are actually doing is creating a POST request where the file's data is copied into the request stream.
Within that stream you have the usual suspects (headers and so forth) plus one or more sections that are bracketed by (hopefully) unique text streams. If the contents of that particular section are binary, they are converted to text using a modulo-64 scheme that ensures that every binary byte is converted to 2 characters, since HTTP was designed to be bounced between multiple systems as text streams and not all of the original Internet machines spoke ASCII (IBM mainframes, in particular).
The client doesn't have the intelligence to send the parts separately, nor does the server. It's not in the HTTP protocol. The closest approximation would be "chunking", but that's for fragmenting the data stream by byte count, not content. On the server side, the POST pre-processor will recognize the sections and split them out when a MIME-MULTIPART post comes in, but that's independent of the data transport. It can't reach back upstream and force a termination, much less a "skip data" request.
Going back to basics, all HTTP is a request/response cycle with a 1-to-1 request-to-response ratio. So in other words, your POST isn't multiple requests, it's a single request, and it results in a single response - the same reason why a single web request cannot return multiple files going the other direction.
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