(Java) Building a multipart/form-data Request for HTTP Upload

Uploading files to a web server typically requires building a multipart/form-data request where the files are contained in the sub-parts of the MIME request.

Note: HTTP uploads require code on the server-side to receive the upload. For example, see Complete C# ASP.NET HTTP Upload Example

This example produces the following HTTP multipart/form-data request:

POST /something HTTP/1.1
Content-Type: multipart/form-data; boundary=------------070002080409050901090203
Host: domain
Content-Length: 546

--------------070002080409050901090203
Content-Disposition: form-data; name="fileA"; filename="fileA.txt"
Content-Type: text/plain

This is the contents of file A
--------------070002080409050901090203
Content-Disposition: form-data; name="fileB"; filename="fileB.txt"
Content-Type: text/plain

This is the contents of file B
--------------070002080409050901090203
Content-Disposition: form-data; name="fileC"; filename="fileC.txt"
Content-Type: text/plain

This is the contents of file C
--------------070002080409050901090203--

Chilkat Java Downloads Java Libs for Windows, MacOS, Linux, Alpine Linux, Solaris Java Libs for Android

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example demonstrates building a multipart/form-data request.

    CkHttpRequest req = new CkHttpRequest();

    // The ContentType, HttpVerb, and Path properties should
    // always be explicitly set.
    req.put_HttpVerb("POST");
    req.put_Path("/something");
    req.put_ContentType("multipart/form-data");

    // The contents and name of each file to be uploaded is provided
    // by calling any of the following methods:
    // AddBytesForUpload
    // AddBytesForUpload2
    // AddFileForUpload
    // AddFileForUpload2
    // AddStringForUpload
    // AddStringForUpload2

    // For this example, we'll provide the contents of the files to be uploaded
    // directly as in-memory strings.
    req.AddStringForUpload("fileA","fileA.txt","This is the contents of file A","utf-8");
    req.AddStringForUpload("fileB","fileB.txt","This is the contents of file B","utf-8");
    req.AddStringForUpload("fileC","fileC.txt","This is the contents of file C","utf-8");

    // View the request that would be sent if SynchronousRequest was called:
    String requestMime = req.generateRequestText();
    System.out.println(requestMime);

    // A few important comments about the HTTP request that is generated:
    // 
    // 1) Chilkat automatically generates a random boundary string.   In 99.999% of cases, this should 
    //    be sufficient.
    // 2) The Content-Length header is automatically generated based on the actual length of the MIME message
    //    that follows the intial (topmost) MIME header.
    // 3) The HOST header will automatically get filled in with the actual domain when SynchronousRequest
    //    is called
  }
}