How to convert Java String to Bytes32 in Java ? I am using web3j solidity wrapper to interact with Smart contract. I am getting following error:

Question

java.lang.UnsupportedOperationException: Input byte array must be in range 0 < M <= 32 and length must match type

I am trying to do as given below. I wanted to add the people but wrapper generated in web3j throwing the error above:

String s = "Rahul"; 
//System.out.println(s.getBytes().length);
Bytes32 b1=new Bytes32(s.getBytes());
contract.addPerson(b1,new Uint256(new BigInteger("35"));

Answer 1

It is best to use the JVM runtime library whenever possible; that code is usually of high quality, although exceptions do exist. In the following code I first create a byte[], then derive a hex value by calling DatatypeConverter.printHexBinary.

byte[] byteArray = "This string is converted to a byte array".getBytes();
String hexValue = javax.xml.bind.DatatypeConverter.printHexBinary(byteArray);

Answer 2

Not sure if you still need solution but as it this is still unanswered and for other who may need.

str.getBytes() only returns byte of that string but actual process is but long.

The main problem is Bytes32(byte[]) only supports 32 length byte[]. Also keep in mind Numeric.hexStringToByteArray(strValueInHex) converts any Hex value of String to byte[].

This is the process

Note: "00" = 1 length Hex & 2 length String

String => Hex => 32 length Hex (ie. 64 length HexString) => byte[] => Bytes32

Here is How I achieved String to Bytes:

String to 64 length HexString:

// String to 64 length HexString (equivalent to 32 Hex lenght)
public static String asciiToHex(String asciiValue)
{
    char[] chars = asciiValue.toCharArray();
    StringBuffer hex = new StringBuffer();
    for (int i = 0; i < chars.length; i++)
    {
        hex.append(Integer.toHexString((int) chars[i]));
    }

    return hex.toString() + "".join("", Collections.nCopies(32 - (hex.length()/2), "00"));
}

64 length HexString to 32 length byte[]:

byte[] myStringInByte = Numeric.hexStringToByteArray(asciiToHex("myString"));

32 length byte[] to Bytes32:

Bytes32 myStringInBytes32 = new Bytes32(myStringInByte);