in core/java8/proxy/src/main/java/org/apache/openwhisk/runtime/java/action/JarLoader.java [43:55]
public static Path saveBase64EncodedFile(InputStream encoded) throws Exception {
Base64.Decoder decoder = Base64.getDecoder();
InputStream decoded = decoder.wrap(encoded);
File destinationFile = File.createTempFile("useraction", ".jar");
destinationFile.deleteOnExit();
Path destinationPath = destinationFile.toPath();
Files.copy(decoded, destinationPath, StandardCopyOption.REPLACE_EXISTING);
return destinationPath;
}