How to get hash and signature of payload parameters using java

Question

I want to use openSea's api, but I don't know how to get the hash and signature of this json object using java.

https://docs.opensea.io/reference/create-an-order

{
"parameters": {
    "offerer": "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266",
    "zone": "0x004C00500000aD104D7DBd00e3ae0A5C00560C00",
    "zoneHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
    "startTime": "0",
    "endTime": "1656044994000",
    "orderType": 0,
    "offer": [
        {
            "itemType": 2,
            "token": "0x0165878A594ca255338adfa4d48449f69242Eb8F",
            "identifierOrCriteria": "1",
            "startAmount": "1",
            "endAmount": "1",
        },
    ],
    "consideration": [
        {
            "itemType": 0,
            "token": "0x0000000000000000000000000000000000000000",
            "identifierOrCriteria": "0",
            "startAmount": "9750000000000000000",
            "endAmount": "9750000000000000000",
            "recipient": "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266",
        },
        {
            "itemType": 0, 
            "token": "0x0000000000000000000000000000000000000000",
            "identifierOrCriteria": "0",
            "startAmount": "250000000000000000",
            "endAmount": "250000000000000000",
            "recipient": "0x70997970C51812dc3A010C7d01b50e0d17dc79C8",
        },
        {
            "itemType": 0, 
            "token": "0x0000000000000000000000000000000000000000",
            "identifierOrCriteria": "0",
            "startAmount": "500000000000000000",
            "endAmount": "500000000000000000",
            "recipient": "0x8a90cab2b38dba80c64b7734e58ee1db38b8992e",
        },
    ],
    "totalOriginalConsiderationItems": 2,
    "salt": 12686911856931635052326433555881236148,
    "conduitKey": "0x0000007b02230091a7ed01230072f7006a004d60a8d4e71d599b8104250f0000",
    "nonce": 0,
},
"signature": "0x",

"protocol_address": "0x00000000000001ad428e4906aE43D8F9852d0dD6", }

Answer 1

OpenSeaOrder.json

demo

{
  "domain": {
    "chainId": 5,
    "name": "Seaport",
    "verifyingContract": "0x00000000000000ADc04C56Bf30aC9d3c0aAF14dC",
    "version": "1.5"
  },
  "message": {
    "offerer": "0x6278A1E803A76796a3A1f7F6344fE874ebfe94B2",
    "zone": "0x004C00500000aD104D7DBd00e3ae0A5C00560C00",
    "offer": [
      {
        "itemType": "2",
        "token": "0x97f236E644db7Be9B8308525e6506E4B3304dA7B",
        "identifierOrCriteria": "111",
        "startAmount": "1",
        "endAmount": "1"
      }
    ],
    "consideration": [
      {
        "itemType": "0",
        "token": "0x0000000000000000000000000000000000000000",
        "identifierOrCriteria": "0",
        "startAmount": "1082250000000000000",
        "endAmount": "1082250000000000000",
        "recipient": "0x6278A1E803A76796a3A1f7F6344fE874ebfe94B2"
      },
      {
        "itemType": "0",
        "token": "0x0000000000000000000000000000000000000000",
        "identifierOrCriteria": "0",
        "startAmount": "27750000000000000",
        "endAmount": "27750000000000000",
        "recipient": "0x0000a26b00c1F0DF003000390027140000fAa719"
      }
    ],
    "orderType": "0",
    "startTime": "1686193412",
    "endTime": "1688785412",
    "zoneHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
    "salt": "24446860302761739304752683030156737591518664810215442929818227897836383814680",
    "conduitKey": "0x0000007b02230091a7ed01230072f7006a004d60a8d4e71d599b8104250f0000",
    "counter": "0"
  },
  "primaryType": "OrderComponents",
  "types": {
    "EIP712Domain": [
      {
        "name": "name",
        "type": "string"
      },
      {
        "name": "version",
        "type": "string"
      },
      {
        "name": "chainId",
        "type": "uint256"
      },
      {
        "name": "verifyingContract",
        "type": "address"
      }
    ],
    "OfferItem": [
      {
        "name": "itemType",
        "type": "uint8"
      },
      {
        "name": "token",
        "type": "address"
      },
      {
        "name": "identifierOrCriteria",
        "type": "uint256"
      },
      {
        "name": "startAmount",
        "type": "uint256"
      },
      {
        "name": "endAmount",
        "type": "uint256"
      }
    ],
    "ConsiderationItem": [
      {
        "name": "itemType",
        "type": "uint8"
      },
      {
        "name": "token",
        "type": "address"
      },
      {
        "name": "identifierOrCriteria",
        "type": "uint256"
      },
      {
        "name": "startAmount",
        "type": "uint256"
      },
      {
        "name": "endAmount",
        "type": "uint256"
      },
      {
        "name": "recipient",
        "type": "address"
      }
    ],
    "OrderComponents": [
      {
        "name": "offerer",
        "type": "address"
      },
      {
        "name": "zone",
        "type": "address"
      },
      {
        "name": "offer",
        "type": "OfferItem[]"
      },
      {
        "name": "consideration",
        "type": "ConsiderationItem[]"
      },
      {
        "name": "orderType",
        "type": "uint8"
      },
      {
        "name": "startTime",
        "type": "uint256"
      },
      {
        "name": "endTime",
        "type": "uint256"
      },
      {
        "name": "zoneHash",
        "type": "bytes32"
      },
      {
        "name": "salt",
        "type": "uint256"
      },
      {
        "name": "conduitKey",
        "type": "bytes32"
      },
      {
        "name": "counter",
        "type": "uint256"
      }
    ]
  }
}

Get order hash

CalcOpenseaOrderHash

package com.utils;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.SignatureException;
import java.util.HashMap;
import org.web3j.crypto.StructuredDataEncoder;
import org.web3j.utils.Numeric;

public class CalcOpenseaOrderHash {
    private static String jsonMessageString;

    public static void main(String[] args) throws SignatureException, Exception {

        String JSONFilePath = "./OpenSeaOrder.json";
        jsonMessageString = new String(
                Files.readAllBytes(Paths.get(JSONFilePath).toAbsolutePath()), StandardCharsets.UTF_8);
        System.out.println(jsonMessageString);
        StructuredDataEncoder dataEncoder = new StructuredDataEncoder(jsonMessageString);
        //
        byte[] structHashDomain = dataEncoder.hashDomain();

        String structHashDomainString = Numeric.toHexString(structHashDomain);
        System.out.println("keccak256(abi.encode(typeHash, nameHash, versionHash, block.chainid, address(this))):");
        System.out.println(structHashDomainString);

        // TODO: orderHash
        byte[] dataHash = dataEncoder.hashMessage(
                dataEncoder.jsonMessageObject.getPrimaryType(),
                (HashMap<String, Object>) dataEncoder.jsonMessageObject.getMessage());
        String dataHashString = Numeric.toHexString(dataHash);
        System.out.println("keccak256(abi.encode(TYPE_HASH, parameters)):");
        System.out.println("orderHash: " + dataHashString);
    }
}