这是我在私人网络中的简单合约
contract AB {
/* This creates an array with all balances */
mapping (address => uint256) public balanceOf;
/* Initializes contract with initial supply tokens to the creator of the contract */
function AB () {
balanceOf[msg.sender] = 1200; // Give the creator all initial tokens
}
/* Send coins */
function transfer(address _to, uint256 _value) {
if (balanceOf[msg.sender] < _value) throw; // Check if the sender has enough
if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
balanceOf[msg.sender] -= _value; // Subtract from the sender
balanceOf[_to] += _value; // Add the same to the recipient
}
function gettokenBalance(address to)constant returns (uint256){
return balanceOf[to];
}
}
我使用web3J生成了智能合约包装器,并且有像
这样的功能public Future<Uint256> gettokenBalance(Address to) {
Function function = new Function("gettokenBalance",
Arrays.<Type>asList(to),
Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
return executeCallSingleValueReturnAsync(function);
}
当我试图访问我的合同函数时,如
AB newAB = AB.load(contractaddress, web3j, credentials, gasprice, gaslimit);
Future<Uint256> result = newAB.gettokenBalance(new Address(address));
LOGGER.info("result:::"+result.get());
它给了我一个像
这样的例外 java.util.concurrent.ExecutionException: java.lang.IndexOutOfBoundsException: Index: 0
at java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:357) ~[na:1.8.0_91]
at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1895) ~[na:1.8.0_91]
at com.belrium.service.UserWalletService.check(UserWalletService.java:197) ~[classes/:na]
at com.belrium.controller.UserController.check(UserController.java:119) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_91]
请帮忙。
答案 0 :(得分:0)
期货是异步的,因此get()
将尝试获取当前仍在计算的结果值。它只在计算完成后才有效。
我认为Java Future API不支持你想要的东西。相反,我建议使用CompletableFuture
,其join()
方法可以完全按照您的要求执行:等待和获取。
当我从合同中生成代码时,我遇到了同样的问题。所以我抛弃了生成器并用Future
s替换了生成的代码中的所有CompletableFuture
。我认为这是对web3j的疏忽,虽然可能有不同的方法来处理我不知道的这个问题!