Parsing Multipart Message With Byte Array InputStream - Loosing Information?

I just wrote a small but working code to parse a multipart message with two files binary encoded.

Problem is, after splitting the content of the files is reduced to normal "alphabetic" digits, and i dont know why.

I just appended my source code and a test file ( multipart ). And the result of my parsing. (part_0 = json, part_1 = file, part_2 = file)

Unfortunately, i dont know, if the Spring FW provides an easier way of doing so at all. Haven't found it yet.

Java Code:

String requestUrl = "http://localhost:8888/";
RestTemplate restTemplate = new RestTemplate();
restTemplate.getMessageConverters().add(new ByteArrayHttpMessageConverter());
HttpEntity<String> entity = new HttpEntity<String>("test");
ResponseEntity<byte[]> response = restTemplate.exchange(requestUrl, HttpMethod.GET, entity, byte[].class);

[Code] .....