Questions tagged [ethereumj]
For questions regarding the installation or use of EthereumJ, a Java library that implements the Ethereum protocol.
153
questions
0
votes
2answers
30 views
Calling smart contract functions and submitting transacions in BACK-END in high level
I have read some references to create ethereum transactions by a BACK-END server, all in low level, for example, requiring that I control the nonce by myself. Are there safe ways to avoid this control ...
-1
votes
1answer
31 views
How and when should I use a Ethereum smart contract in document verification process?
First, a student applies for a certificate in his/her University . The University creates his degree certificate . Now , how do I write a smart contract in Solidity so that anyone in blockchain can ...
1
vote
2answers
74 views
Cannot install web3 on nodejs
When I try to install web3 using 'npm install ethereum/web3.js --save' command, I get the following error messages-
npm ERR! path git
npm ERR! code ENOENT
npm ERR! errno ENOENT
npm ERR! syscall ...
0
votes
2answers
18 views
Why am I getting TypeError: Member “balanceOf” not found or not visible after argument?
On line 22 my code is -- require(tokenContract.balanceOf(this) >= _numberOfTokens);
This gives the error message
TypeError: Member "balanceOf" not found or not visible after argument-dependent ...
0
votes
1answer
22 views
Why am I getting a Parse Error in my smart contract after the constructor?
I'm writing a token sale smart contract & my original error was my function had the same name as the contract and I changed it to a constructor because the contract cant have the same name as the ...
1
vote
1answer
40 views
Issue Deploying Contract LinkedIn Course - Ethereum: Building Blockchain Decentralized Apps (DApps)
I'm completely new to Ethereum Smart Contracts. I'm following the course on LinkedIn [Ethereum: Building Blockchain Decentralized Apps (DApps)].
I've been able to compile the smart contract as per ...
0
votes
1answer
54 views
Use uint40 for time in Solidity?
My question is: Should I use uint40 for time in Solidity?
All the examples I've seen use uint256 for time, however, I think it's too wasteful -- while using uint32 is maybe a little aggressive due to ...
0
votes
3answers
239 views
web3.eth.sendSignedTransaction executed successfully but never any ETH transferred actually
as you see in below, i the raw transaction has been set by the gas simplify value, the returned value is an implemented transaction hashcode, but never assumed result by this transaction figure out
...
2
votes
1answer
26 views
How Ethereum HardFork Complete?
When a major change happen in ethereum like Softfork or Hardfork, all nodes may not agree with this. So is this change possible ?
Vitalik is creator of Ethereum. But ethereum is totally decentralized, ...
1
vote
0answers
39 views
How to run private node on EthereumJ
I would like to run a private node on EthereumJ. I don't know how to start mining on EthereumJ and how to start EthereumJ node. I will be very grateful if someone tell me where to start looking (...
1
vote
2answers
97 views
How to convert smallest unit of ERC20 with less than 18 decimals to full coins without rounding errors?
I can just use web3's fromWei function for all token that have 18 decimal places but I'm not sure how to convert token to full token without having to worry about rounding errors.
For example convert ...
0
votes
0answers
21 views
How to completely empty an Ethereum wallet using W3.py
I have an ethereum wallet, I need to calculate the amount to completely empty the wallet.
So currently i calculate the needed gas like this,
needed_gas = w3.eth.gasprice * 210000
amount_to_send = ...
0
votes
1answer
122 views
Query Ethereum Blockchain for functions return value of a Specified Smart Contract
I want to get smart contract functions return value sent by a specified smart contract within a range of blocks.
I found a [manual] working method to achieve this:
async function getTxsByAccount(...
1
vote
1answer
69 views
Truffle test failing
i am learning solidity contracts and ethereum dapps. I have created a smart contract for creating a ERC20 token on using truffle dev environment.
pragma solidity ^0.5.0;
contract LearnTokens {
...
1
vote
1answer
136 views
How to get the same SHA3 hash as soliditySHA3(ethereumjs-abi) returns using web3.sha3 in js?
I'm trying to hash a message as shown here:
function constructPaymentMessage(contractAddress, amount) {
return ethereumjs.ABI.soliditySHA3(
["address", "uint256"],
[contractAddress, amount],...
0
votes
0answers
173 views
Encryption with Ethereum Keys for all Clients (iOS,Android,Web)
I was trying to encrypt data with Ethereum Key pairs. So far, I have managed to encrypt and decrypt data with these keys using ECIES schema on eth-crypto. Eth-crypto is a package which is built on top ...
1
vote
2answers
190 views
Pass specific address in Web3J send method
How to pass specific address in send method in Web3J?
For example, using web3 javascript library, we can pass from address like below.
contract.someMethod().send({ from: this.props.accounts[0] })
...
0
votes
0answers
36 views
Zero balance and double entrance
I am unable to set balance to zero to all of the subscriber except the winner so that winners gets the complete pool prize and other gets zero balance.
Also how can I prevent a subcriber for a double ...
1
vote
1answer
9 views
Token Transferring issue to the respective winner
My code has a function which randomly select a subscriber from the list and all of the sum of the tokens should transfer to the winner account address. but unfortunately it is not working for me.
...
0
votes
0answers
83 views
Deploying Smart Contract through EthereumJ (Java)
I have been stuck here for a while now. I am tried to deploy my smart contract using the EthereumJ library. here are my codes:
pragma solidity ^0.4.22;
contract MyNotaryEntry {
string fileName;
...
1
vote
0answers
81 views
How to write a mock method for getting ether balance using Web3j Api. I am trying to mock Web3j and callig EthGetBalance method but I am getting Null
public static BigInteger OriginalMethod(){
// connect to node
Web3j web3 = Web3j.build(new HttpService()); // defaults to
http://localhost:8545/
// send asynchronous requests to get balance
...
0
votes
1answer
68 views
Unable ts start Bootnode, am new to private blockchian, Can anyone tell me what am i missing
bootnode : The term 'bootnode' is not recognized as the name of a cmdlet,
function, script file, or operable program. Check the spelling of the name,
or if a path was
included, verify that the path ...
1
vote
1answer
738 views
Could not find artifacts for ./Election from any sources
I tried solutions provided in ethereum stack, but nothing worked for me.
My smart contract file:
pragma solidity ^0.4.15;
contract Election {
string public candidate;
function Eletion () ...
1
vote
1answer
268 views
How do I call the burnFrom() function once my contract is deployed?
I'm using the Openzeppelin library in my contract where MyToken is StandardBurnableToken. Once I deploy that and I want to burn a set amount of the initial supply how do I call the function? I don't ...
0
votes
1answer
323 views
web3j.ethSendRawTransaction wait until the transaction is successfully mined - Web3j
Im trying to send 0 ether to the same account with Web3j, however when i run this code it give me directly the transaction hash, even if the transaction has not been mined yet and still pending. I can'...
0
votes
1answer
639 views
retry mechanism for transactions in web3j
In my Java-web-application I have (with one click) to send about 120 transactions after each other from the same address to the same smartcontract.
My question: is there any java libraries or ...
0
votes
1answer
99 views
Run solidity bytecode with ethereumj
I am a newbie to Ethereum and I would like to run some simple smart contract code written in Solidity locally with my ethereumj virtual machine.
I am aware of how to use EVM and aleth-vm to run some ...
1
vote
1answer
250 views
Cannot connect to parity JSONRPC from local machine
Here is my parity config:
[rpc]
disable = false
port = 8545
interface = "all"
cors = ["*"]
apis = ["web3", "eth", "pubsub", "net", "parity", "parity_pubsub", "traces", "rpc", "shh", "shh_pubsub"]
...
0
votes
2answers
26 views
Struct Properties Cannot Be Identified
I have been learning Solidity and I have run into a scoping issue with the structs. I thought by default, all properties of a struct are put into storage. When I try to add the battles variable as an ...
3
votes
2answers
65 views
Dual blockchain
Could anybody please help me to understand how dual blockchains work? There are many Dapps which are built on dual blockchains, especially using the combination of Ethereum and Hyperledger.
But I am ...
0
votes
1answer
88 views
LoadCredentials function returns file not found exception
I am using the following code to deploy my contract:
@RequestMapping("/")
public String index() throws Exception {
Web3j web3j = Web3j.build(new HttpService("https://rinkeby.infura.io/v3/...
1
vote
0answers
75 views
Ethj spring boot blockchain transaction app error the method subscribe is undefined for the type object
package org.web3j.web3jspringbootstarter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure....
1
vote
1answer
112 views
How can I increase the nonce in Smart Contract?
We all know that the nonce of smart contract can be added 1 time when one subcontract is created using solidity.
I'd like to know if the creation of subcontract is the only way to increase nonce.
If ...
0
votes
0answers
166 views
Transfer tokens among multiple accounts in single function
I want the user to transfer tokens to an wallet instead of smart contract.
function getTokens () public {
require (token.transferFrom(msg.sender, address(this), amount));
require (token....
1
vote
0answers
84 views
Why transaction hash isn't available inside solidity function call
I recently bumped into this
Is it possible to get the transaction hash from within a Solidity function call? while I was looking for a way to save the transaction hash inside my contract. And ...
1
vote
2answers
1k views
How to get public key from private key in Web3j
I am developing Dapp by web3j and I attempt to convert private key to public key. I found this question this question that provides a way converting private key to public key in class ECKey, but I ...
0
votes
1answer
136 views
Gas refund uint8 array vs uint256 array
I am trying to understand how gas refunds work. I made this toy contract that fills in an array and separately does some work (loop a ton of times) and then deletes from the array to save on gas. See ...
1
vote
0answers
76 views
Out of Gas Exception
I have a smart Contract which generates a random number within a range and then check if the number is equal to the user's input.
For the same input sometimes it works and sometimes it gives me ...
1
vote
1answer
143 views
DApp owner pays for the transaction without invoking smart contract
I am working on a chrome extension (crypto wallet) that lets you use one of our custom ERC20 token to make a purchase on websites. Most of the users of the extension don't have Ethereum in their ...
1
vote
2answers
364 views
Storing data on IPFS using KMS and ethereum
I am trying to build a blockchain on ethereum but keeping the data related to blocks in some distributed file storage system like IPFS or Storj and storing the hash of data in blocks. But we need our ...
5
votes
4answers
425 views
Why do you want to use different implementations of EVM?
Currently there are many implementations of EVM (Java, C++, Python, Go, etc).
For example: I will be using Solidity to write DApp on the top of EVM-Java and EVM-Python, why would I want to use EVM-...
2
votes
1answer
445 views
How to generate deterministic keypairs using ed25519
I am trying to implement my wallet using ed25519 curve, i was using tweetnacl from this link "https://github.com/dchest/tweetnacl-js" its working, But i want to generate deterministic key-pair ...
0
votes
1answer
37 views
Smart Contract (SC) - Is it a Block itself?
Is SC a block itself on the Ethereum Block chain or it's just a storage? I know SC has its own hash address, it's own data stored in State variables, but does it has nonce and gas limit?
2
votes
2answers
1k views
How to use Solidity solc to compile A.sol that imports B.sol file?
I know how to install solc via "npm install --save solc"
then use solc.compile to compile one sol file. But now I've got A.sol file that imports B.sol file, and when I run node compile.js, no error in ...
1
vote
1answer
233 views
Sending tokens via ethereumj. How create data block for transaction?
I am trying to send Plasma tokens in testnet but unfortunately misunderstand how I should create transaction properly.
I try to create tx like this:
String privateKeyString = "xxx";
BigInteger ...
1
vote
0answers
64 views
How to get transactions history details of specific account using Ethereum API [duplicate]
How to get transactions history details of specific account using Ethereum API
currently i am using Ethereum API got get list of transactions based on ontract address, but i need full details of ...
0
votes
2answers
441 views
After truffle init I don't see MetaCoin.sol and other files expected to be there?
I have Truffle installed on an Ubuntu 14.04 LTS box. Here are my Truffle and Solidity version numbers:
Truffle v4.0.6 (core: 4.0.6)
Solidity v0.4.19 (solc-js)
I am following along the Blockgeeks "...
1
vote
1answer
151 views
How to make user sign up and login on my decentralized application?(on production it should work without metamask)
Assuming that user who is going to signup is not having any ethereum account so how can I generate a public, private key and address for ethereum and make use of it to make further transactions.
Users ...
0
votes
4answers
698 views
how much does using ethereum services cost
Lets say im creating my own cryptocurrency and my own blockchain on ethereum, what would be the basic costs for setting all this up if i am developing on Ethereum
1
vote
3answers
921 views
How to access ethereum smart contract(already deployed) in a Java application via its address using web3j?
I have an existing Smart contract address,abi,binary code.
I need to access it from a Java application.Is it possible to do this without creating a java wrapper class?
