[java] multipart/form-data POST request using Java | mailgun with attachment

        CredentialsProvider credsProvider = new BasicCredentialsProvider();

        credsProvider.setCredentials(

                new AuthScope(HOST_NAME, PORT),

                new UsernamePasswordCredentials(USER_NAME, TOKEN));

        CloseableHttpClient httpclient = HttpClients.custom()

                .setDefaultCredentialsProvider(credsProvider)

                .build();

        try {

            HttpPost httpPost = new HttpPost(BASE_URL + EMAIL_API_NAME);


            MultipartEntityBuilder builder = MultipartEntityBuilder.create();


            builder.addBinaryBody("attachment", new File("D:/opt/test.pdf"), ContentType.APPLICATION_OCTET_STREAM, "file.ext");

            builder.addTextBody("from", FROM_ADDRESS, ContentType.APPLICATION_JSON);

            builder.addTextBody("to", toEmail, ContentType.APPLICATION_JSON);

            builder.addTextBody("bcc", bcc, ContentType.APPLICATION_JSON);

            builder.addTextBody("subject", subject, ContentType.APPLICATION_JSON);

            builder.addTextBody("html", this.loadTemplate(template, values), ContentType.APPLICATION_JSON);

            HttpEntity multipart = builder.build();

            httpPost.setEntity(multipart);

            CloseableHttpResponse response2 = httpclient.execute(httpPost);

            log.info(response2.toString());


            try {

                System.out.println(response2.getStatusLine());

                HttpEntity entity2 = response2.getEntity();

                // do something useful with the response body

                // and ensure it is fully consumed

                EntityUtils.consume(entity2);

            } finally {

                response2.close();

            }

        } finally {

            httpclient.close();

        }

ref:http://stackoverflow.com/questions/1378920/how-can-i-make-a-multipart-form-data-post-request-using-java