Questions tagged [ethereumj]

For questions regarding the installation or use of EthereumJ, a Java library that implements the Ethereum protocol.

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1answer
31 views

Smart Contract Application in ASP>NET [closed]

I just have started to learn Smart Contract. I have to design front end in ASP.NET. Can I call Contract from it?
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1answer
21 views

Truffle Migrate

What happens when there is a minor change in the smart contract and I run truffle migrate command. Example: //before contract test{ function display() public returns (string){ return "...
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1answer
21 views

Having a problem compiling a ERC20 token smart contract - Code inside

Basically i'm using a cut and paste erc20 token code from this site: https://hashnode.com/post/how-to-build-your-own-ethereum-based-erc20-token-and-launch-an-ico-in-next-20-minutes-...
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21 views

Just not able to install Web3 through powershell

After reading a lot of articles about how to install Web3j in windows. I also tried following this article : https://kauri.io/generate-a-java-wrapper-from-your-smart-contract/...
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31 views

TypeError: Operator != not compatible with types string storage ref and int_const 0

Im using blockchain technology for the first time, for a college project. Im trying to run a smart contract from Github (in Powershell windows 10). Im unable to compile the contract due the following ...
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1answer
27 views

Im getting the following error: ParserError: Expected primary expression. struct ManagingOrder.Parking memory new_Parking = Parking({

Im using blockchain technology for the first time, for a college project. Im trying to run a smart contract from Github. After debugging the errors shown while compiling the smart contract (in ...
1
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1answer
29 views

Value of emitted events in App.js

Actually in my App.js I have called my contract function like this: [ this.state.swapcontract.methods.sendFunds(address).send({ from: this.state.account , value:amount}) ] The function is called ...
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1answer
46 views

Can we use secp256r1 to generate valid Ethereum address instead of secp256k1?

We interact with HSM via Graphene to generate EC public/private key for Ethereum blockchain, many tutorials say secp256k1 to generate valid Eth address, however the Graphene supports only secp256r1
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0answers
97 views

get event logs and debug trace from eth_call

I am looking for a way to execute a transaction locally (using local geth/parity node) for simulation only, before actually submitting it to blockchain. I know that I can use 'eth_call' RPC call and ...
0
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1answer
36 views

How to resolve this error in solidity “The constructor should be payable if you send value.”?

In this solidity code the finalizeRequest() is giving a run-time error. Here is the error : Campaign.finalizeRequest(uint256) 0x692...77b3a transact to Campaign.finalizeRequest errored: VM error: ...
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0answers
43 views

Not able to decode the input data from transaction using web3j (Java)

I am creating transactions using web3j and passing some private data in that transaction. The transaction is also getting mined . I have subscribed to the mined blocks, where I am fetching the ...
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2answers
40 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 ...
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1answer
110 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 ...
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2answers
105 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 ...
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2answers
37 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 ...
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1answer
40 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 ...
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1answer
47 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 ...
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1answer
90 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 ...
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3answers
381 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
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1answer
43 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, ...
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0answers
46 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 (...
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2answers
192 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 ...
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0answers
24 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 = ...
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1answer
205 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(...
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1answer
98 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 { ...
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2answers
214 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],...
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2answers
297 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] }) ...
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1answer
13 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. ...
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0answers
107 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 ...
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1answer
82 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 ...
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2answers
947 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 () ...
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1answer
339 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 ...
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1answer
445 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'...
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1answer
1k 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
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1answer
123 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 ...
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1answer
338 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"] ...
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2answers
29 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 ...
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2answers
77 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 ...
1
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1answer
109 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/...
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0answers
80 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....
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1answer
144 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 ...
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0answers
179 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....
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0answers
89 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 ...
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2answers
2k 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 ...
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1answer
157 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 ...
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0answers
79 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 ...
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1answer
178 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 ...
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2answers
389 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 ...
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4answers
484 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
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1answer
568 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 ...