Transfer file to WebService and Encode/Decode base64 string

I had a task where I should give opportunity to user send file to WebService written on Java. File always should come as decode base64 string, and in WebService I should decode string to normal (it should be DXL content as result) and then import it in a special database, so I had small problem with decode/encod (dont know why but it was happen). So here this simple exmplae how to do it

public class Base64Test {
public static void main(String[] args) throws IOException {
String str = "my string";

String s = new BASE64Encoder().encode(str.getBytes("UTF-8"));
byte[] bytes = new BASE64Decoder().decodeBuffer(s);
String result = new String(bytes, "UTF-8");
System.out.println(result);
}
}