How to display hashed MD5 value as text displayed in H2?

The H2 HASH function returns bytes, and SELECT HASH('MD5', 'test') AS new_id FROM my_table; displays a text value: 098f6bcd4621d373cade4e832627b4f6

How to retrieve that same text value in Java? Using ResultSet.getBytes("new_id") gives the object’s address, something like [B@48f278eb. Feeding that through new String(ResultSet.getBytes("new_id"), StandardCharsets.UTF_8) gives gobbledygook: �Oh�؆nr�Mz��.

Answer

The reason you see [B@48f278eb is because the resulting MD5 hash is in bytes in a non-string format.

Here is a complete example of generating the MD5 hash and converting the resulting bytes to a string by using a StringBuilder and formatting it String.format("%02x", b):

String text = "test";   
//Generate MD5 hash
byte[] bytesOfMessage = text.getBytes("UTF-8");
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] arr = md.digest(bytesOfMessage);

//Convert the bytes to a string
StringBuilder strBuilder = new StringBuilder();
    for(byte b:arr){
        strBuilder.append(String.format("%02x", b));
    }

//The complete string
String strHash = strBuilder.toString();

//Print or use the string
System.out.println("The MD of " + text + " is " + strHash);

And the output is as expected:

The MD of test is 098f6bcd4621d373cade4e832627b4f6