The problem is that when you append the byte array to the String it calls toString on the byte[] which prints the unhelpful pointer you are seeing. You need to manually convert it to a String for your data type. In your case you are using a blob, so you need to convert to a hex string.
This question has code for converting the byte[] to String:
How to convert a byte array to a hex string in Java?
You can use one of those functions and prepend '0x' to it. Then you should have a valid String for your blob.