Nifi multipart form

You could use ExecuteGroovyScript processor with the following code to build multipart/form-data:

@Grab(group='org.apache.httpcomponents', module='httpmime', version='4.5.9')

import org.apache.http.entity.mime.MultipartEntityBuilder
import org.apache.http.entity.ContentType

def ff = session.get()
if(!ff)return

def multipart

ff.write{streamIn, streamOut->
    multipart = MultipartEntityBuilder.create()
        //specify multipart entries here
        .addTextBody( "username", ff.filename ) //get from flowfile attribute "filename"
        .addTextBody( "secret", new File("./README").getText("UTF-8") ) //add text body from file
        .addBinaryBody( "avatar", streamIn, ContentType.DEFAULT_BINARY, ff.filename )   //add flowfile content as binary body
        .build()
    multipart.writeTo(streamOut)
}
//set the `mime.type` attribute to be used as `Content-Type` in InvokeHTTP
ff."mime.type" = multipart.getContentType().getValue()
REL_SUCCESS << ff

check the other add* methods to add multipart parameters: org.apache.http.entity.mime.MultipartEntityBuilder

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To check this code I used InvokeHTTP processor just after ExecuteGroovyScript with only following parameters changed:

• HTTP Method: POST
• Remote URL: http://httpbin.org/post