Get token balance

JSON-RPC API

I use Postman to do HTTP request. My IP address 192.168.xx.xx, and the RPC port of miner2 node is 8487, so I enter IP address 192.168.xx.xx:8487 to be the request URL. Then do the HTTP POST request with below body.

{
  "jsonrpc":"2.0",
  "method":"eth_call",
  "params":[
    {
      "to": "0xf13c9660190749124ad90c8defc77cc6c5d36494",
      "data": "0x70a08231000000000000000000000000aeF72A6461e5392e9fa1537372b98701780a1819"
    },
    "latest"
  ],
  "id":63
}

Then after about 26ms, I got below response.

{
  "jsonrpc": "2.0",
  "id": 63,
  "result": "0x0000000000000000000000000000000000000000000000361abe817294d24000"
}

I can use Web3 to parse that balance of the account of given address.

> web3.fromWei(web3.toBigNumber("0x0000000000000000000000000000000000000000000000361abe817294d24000"), "ether")
998.0513

eth_getBalance

Geth API

I also can use Geth to request token balance.

• TokenBalanceFetcher.java

  public class TokenBalanceFetcher implements Balance {
    /**
     * Fetch the balance of Erc20 Token from ethereum.
     *
     * @return balance is possible less than zero.
     * @throws IllegalStateException when fetch balance failed, such as still trying connect to ethereum.
     */
    @Override
    public BigDecimal fetchBalance() {
      byte[] response;
      final CallMsg callMsg = Geth.newCallMsg();
      try {
        callMsg.setTo(Geth.newAddressFromHex(tokenAddress));
        callMsg.setData(InputData.makeInputDataForBalanceOfMethod(accountAddress));
        Log.d(TAG, "'toAddress is " + callMsg.getTo().getHex());
        Log.d(TAG, "input data is " + InputData.toHexWith0x(callMsg.getData()));
        response = ethereum.pendingCallContract(callMsg);
      } catch (IllegalStateException e) {
        throw e;
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
      if (response == null) {
        throw new IllegalStateException("cannot fetch balance, possible trying connect to other peers in ethereum.");
      }
      Log.d(TAG, "response is " + toHexWith0x(response));
      return toValue(toHexWith0x(response));
    }
  }
  

• GoEthereum.java

  public class GoEthereum implements Ethereum {
  
    byte[] pendingCallContract(@NonNull CallMsg callMsg) throws Exception {
      if (ethereumClient != null) {
        return ethereumClient.pendingCallContract(Geth.newContext(), callMsg);
      } else {
        throw new IllegalStateException("you have to call Ethereum#connect() before invokes this method.");
      }
    }
  }
  

• InputData.java

  import okio.ByteString;
  
  public class InputData {
    public static final String PREFIX_HEX = "0x";
  
    @NonNull
    static String toHexWith0x(@NonNull byte[] data) {
      final String result = ByteString.of(data).hex();
      return hasPrefixWith0x(result) ? result : PREFIX_HEX + result;
    }
  
    public static BigDecimal toValue(@NonNull String hex) {
      final String hexWithoutPrefix0x = hasPrefixWith0x(hex) ? hex.replace(PREFIX_HEX, "") : hex;
      if (hexWithoutPrefix0x.length() > 0) {
        return new BigDecimal(new BigInteger(hexWithoutPrefix0x, 16).toString());
      } else {
        return new BigDecimal(0);
      }
    }
  }
  

EthereumClient#pendingCallContract(Context, CallMsg)