how do i create and post a multipart/mixed http request using Apache HttpComponentst?

Question

I am using Apache HttpComponents v4.3.3 (maven httpclient and httpmime). I need to upload a file with some metadata. The curl command, which works, looks like the following.

curl -k -i -H "Content-Type: multipart/mixed" -X POST --form 'field1=val1' --form 'field2=val2' --form '[email protected];type=application/zip' https://www.some.domain/

I have tried mimicking this curl post as the following.

HttpEntity entity = MultiPartEntityBuilder
 .create()
 .addPart("field1",new StringBody("val1",ContentType.TEXT_PLAIN))
 .addPart("field2",new StringBody("val2",ContentType.TEXT_PLAIN))
 .addPart("file", new FileBody(new File("somefile.zip"), ContentType.create("application/zip"))
 .build();
HttpPost post = new HttpPost("https://www.some.domain");
post.addHeader("Content-Type", "multipart/mixed");

However, after I use HttpClient to execute the HttpPost, I get the following exception (server code is also Java running on Jetty).

org.apache.commons.fileupload.FileUploadException: the request was rejected because no multipart boundary was found

When I add a trace to curl

curl --trace - -k -i -H "Content-Type: multipart/mixed" -X POST --form 'field1=val1' --form 'field2=val2' --form '[email protected];type=application/zip' https://www.some.domain/

I see that the form field/value pairs are set as HTTP headers.

Content-Disposition: form-data; name=field1...value1

Any idea on what I'm doing wrong here? Any help is appreciated.

Answer 1

I tinkered a bit and did two things to get the code working.

• no longer use addPart(...)
• no longer set Content-Type header

Here's the revised snippet that's working in case anyone is interested.

HttpEntity entity = MultipartEntityBuilder
 .create()
 .addTextBody("field1","val1")
 .addTextBody("field2","val2")
 .addBinaryBody("file", new File("somefile.zip"),ContentType.create("application/zip"),"somefile.zip")
 .build();
HttpPost post = new HttpPost("https://www.some.domain");
post.setEntity(entity);

I also set HttpComponents to debug mode.

-Dorg.apache.commons.logging.Log=org.apache.commons.logging.impl.SimpleLog
-Dorg.apache.commons.logging.simplelog.showdatetime=true
-Dorg.apache.commons.logging.simplelog.log.org.apache.http=DEBUG

It turns out that each part now has a boundary. Even better yet, the Content-Type and boundary are autogenerated.

Content-Type: multipart/form-data; boundary=5ejxpaJqXwk2n_3IVZagQ1U0_J_X9MdGvst9n2Tc