Implementing HttpComponent's HttpAsyncClient with Multipart Entity - apache-httpcomponents

Question

I would like some help, clarification on using HttpAsyncClient with multipart entity. Basically I am trying to upload content of a file (byte[]) as a MultiPart Body using HttpAsyncClient.
Sample of how I am using it:
CloseableHttpAsyncClient httpAsyncClient = HttpAsyncClients.createDefault();
httpAsyncClient.start();
MultipartEntityBuilder reqEntity = MultipartEntityBuilder.create();
reqEntity.addPart("file",new ByteArrayBody(Base64.decodeBase64(fileContent),"");
reqEntity.addPart("fileSize",new StringBody("1234"));
reqEntity.addPart("fileName",new StringBody("xyz.txt"));
reqEntity.addPart("fileType",new StringBody("text/plain"));
reqEntity.addPart("SEQ_NUM",new StringBody("23432"));
HttpPost httppost = new HttpPost(endpointUrl);
httppost.setEntity(reqEntity.build());
Future<HttpResponse> future = httpAsyncClient.execute(httppost, null);
httpAsyncClient.close();
Below are the Pom Dependences added to the project for this implementation:
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpasyncclient</artifactId>
<version>4.0.2</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpmime</artifactId>
<version>4.3.6</version>
</dependency>
Now, I am blocked at a place where the following exception is thrown:
java.util.concurrent.ExecutionException: java.lang.UnsupportedOperationException: Multipart form entity does not implement #getContent()
I have did lot of search over the internet and could find very little details about the new HttpAsyncClient implementation. I found some users been asked similar questions but none of the solution worked for me.
[HttpAsyncClient Multipart Entity not working?]
In the below link a user suggested to wrap the MultipartEntity instance with BufferedHttpEntity. So, I updated the code as below(not sure its correct) but still the same exception.
CloseableHttpAsyncClient httpAsyncClient = HttpAsyncClients.createDefault();
httpAsyncClient.start();
MultipartEntityBuilder reqEntity = MultipartEntityBuilder.create();
reqEntity.addPart("file",new ByteArrayBody(Base64.decodeBase64(fileContent),"");
reqEntity.addPart("fileSize",new StringBody("1234"));
reqEntity.addPart("fileName",new StringBody("xyz.txt"));
reqEntity.addPart("fileType",new StringBody("text/plain"));
reqEntity.addPart("SEQ_NUM",new StringBody("23432"));
HttpPost httppost = new HttpPost(endpointUrl);
httppost.setEntity(new BufferedHttpEntity(reqEntity.build()));
Future<HttpResponse> future = httpAsyncClient.execute(httppost, null);
httpAsyncClient.close();
I would appreciate your help in identifying the cause.
References:
http://mail-archives.apache.org/mod_mbox/hc-httpclient-users/201311.mbox/%3c13034392.132.1384195516775.JavaMail.Hal#Harold-Rosenbergs-MacBook-Pro.local%3e
http://mail-archives.apache.org/mod_mbox/hc-httpclient-users/201206.mbox/%3C1339240012.2405.12.camel#ubuntu%3E

Answer 1

MultipartFormEntity can not be used asynchronously. One of the options is to write the entity out to ByteArrayOutputStream and create a NByteArrayEntity out of it.
File file = new File(filePath);
ByteArrayBody body;
body = new ByteArrayBody(FileUtils.readFileToByteArray(file), file.getName());
HttpEntity mEntity = MultipartEntityBuilder.create()
.setBoundary("-------------" + boundary)
.addPart("file", body)
.build();
ByteArrayOutputStream baoStream = new ByteArrayOutputStream();
mEntity.writeTo(baoStream);
HttpEntity nByteEntity = new NByteArrayEntity(baoStream.toByteArray(), ContentType.MULTIPART_FORM_DATA);
httppost.setEntity(nByteEntity );