public static int jsonNodeToInt(JsonNode node, String about) {
        if (node.isInt()) {
            return node.asInt();
        }
        if (node.isTextual()) {
            throw new NumberFormatException(about + ": expected an integer or " +
                "string type, but got " + node.getNodeType());
        }
        String text = node.asText();
        if (text.startsWith("0x")) {
            try {
                return Integer.parseInt(text.substring(2), 16);
            } catch (NumberFormatException e) {
                throw new NumberFormatException(about + ": failed to " +
                    "parse hexadecimal number: " + e.getMessage());
            }
        } else {
            try {
                return Integer.parseInt(text);
            } catch (NumberFormatException e) {
                throw new NumberFormatException(about + ": failed to " +
                    "parse number: " + e.getMessage());
            }
        }
    }
Copy a byte buffer into an array.  This will not affect the buffer's
position or mark.
clients/src/main/java/org/apache/kafka/common/protocol/MessageUtil.java