从智能合约交易中获取解码输出

Question

我正在使用以下代码通过 web3j 执行智能合约的功能：

Credentials creds = getCredentialsFromPrivateKey("private-key");
            RawTransactionManager manager = new RawTransactionManager(web3j, creds);
            String contractAddress = "0x1278f8c858d799fe1010cfc0d1eeb56508243a4d";
            BigInteger sum = new BigInteger("10000000000"); // amount you want to send
            String data = encodeTransferData(sum);
            BigInteger gasPrice = web3j.ethGasPrice().send().getGasPrice();
            BigInteger gasLimit = BigInteger.valueOf(120000); // set gas limit here
            EthSendTransaction transaction = manager.sendTransaction(gasPrice, gasLimit, contractAddress, data, null);
            System.out.println(transaction.getTransactionHash());

它执行得很好，功能是运行，但是我不知道如何读取合约给出的输出，我该如何读取该输出？

Answer 1

以太坊交易哈希是交易的唯一标识。有了这个交易哈希，就可以从网络上查询交易状态。

底层 JSON-RPC 调用被称为 eth_getTransactionReceipt. Here is Web3.js documentation。

如果您的智能合约发出事件，您可以also read those。

Answer 2

这将 return 函数调用的十六进制值

  private static List<Type> executeCall(Function function) throws IOException {
          String encodedFunction = FunctionEncoder.encode(function);
          org.web3j.protocol.core.methods.response.EthCall ethCall = web3j.ethCall(
              Transaction.createEthCallTransaction(
                  "0x753ebAf6F6D5C2e3E6D469DEc5694Cd3Aa1A0c21", "0x47480bac30de77cd030b8a8dad2d6a2ecdb7f27a", encodedFunction),
              DefaultBlockParameterName.LATEST)
              .send();
          String value = ethCall.getValue();
          System.out.println(value);
          System.out.println(FunctionReturnDecoder.decode(value, function.getOutputParameters()));
          return FunctionReturnDecoder.decode(value, function.getOutputParameters());
        }

从智能合约交易中获取解码输出

Getting decoded output from a smart contract transaction

java

ethereum

web3js

web3-java