Questions tagged [web3j]

Lightweight Java and Android library for integration with Ethereum clients

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votes
2answers
856 views

Empty value (0x) returned from contract web3j

I'm trying to deploy a very simple contract on Windows 10, using Web3j 4.2.0. I've created an account using Mist. I've set up one local ethereum node (using geth) on my machine and I'm able to deploy ...
2
votes
1answer
570 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'...
2
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2answers
567 views

How do I update data for project using blockchain (Ethereum)?

I am very new to creating blockchain dapps, so some guidance would be appreciated. I am conceptualizing how to approach creating a private blockchain so that users can communicate about the status of ...
2
votes
1answer
955 views

Should I use Infura with Web3j for Event filter?

I'm using Web3j with Infura for smart contract deployment, calling contract method and transactions. Now I want to use Filter contract event from log. Should I use Infura for this? Is Web3j filter ...
2
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1answer
2k views

Is it possible to call payable functions of smart contract using web3j’s smart contract wrappers?

How do we call payable functions of smart contract using web3j? UPDATE: I'm going to change generated smart contract wrapper class manually. Now I have: public Future<TransactionReceipt&...
2
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2answers
2k views

Deploy smart contracts using web3j java library

I am using web3j java library to deploy a smart contract. // I am encoding the constructor parameters here -- 2 & 3, 10 & 20 String encodedConstructor = FunctionEncoder....
2
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1answer
65 views

transaction receipt was not generated after 600 seconds for transaction

I am running private ethereum blockchain using geth and I am using web3j to send transactions. Since yesterday I am not able to deploy my contract, In my java console I am getting "transaction ...
2
votes
1answer
196 views

org.web3j.protocol.exceptions.TransactionException: Transaction receipt was not generated after 600 seconds for transaction

I am sending a transaction through this code public String transferEthByPk(String amount, String toAddress, String privateKey, Web3j web3j) { BigDecimal value = new BigDecimal(amount); ...
2
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2answers
237 views

Too low nonce error with web3j and rinkeby

All of sudden my application on testnet has stopped working due to low nonce error. No change in source code. My app connects to the network via infura. Any ideas what could be wrong here. java.lang....
2
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1answer
357 views

How to call geth mining through java code manually ?

I am using web3j and Geth and created a private network. However, I want to do the mining manually whenever required, since don't want to jam the server when I am in the development phase. For that, I ...
2
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1answer
422 views

How Can I call contract's function from Java?

There is BizzleTokenSale contract. pragma solidity ^0.4.2; import "./BizzleToken.sol"; contract BizzleTokenSale { address admin; BizzleToken public tokenContract; uint256 public tokenPrice; ...
2
votes
1answer
784 views

Cannot send funds to a smart contract using web3j

I'm trying to send funds to a smart contract using the following code, however, the balance is always 0. TransactionReceipt transactionReceipt = Transfer.sendFunds( web3j, credentials, ...
2
votes
2answers
897 views

Out Of Memory exception when using web3j in Android

I'm trying to integrate web3j in an android application. But the library gives an Out Of Memory exception when loading the wallet file: Credentials credentials = WalletUtils.loadCredentials("password"...
2
votes
1answer
1k views

Insufficient funds error on deploying smart contract

I am writing a Java program to deploy a smart contract. I have created the Java Wrapper class. This is the essence of the code. static final BigInteger GAS_PRICE = BigInteger.valueOf(20_000_000_000L)...
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0answers
40 views

events and relationships between smart contracts and oracle smart contracts [closed]

How to subscribe a web3j client node to a smart Oracle contract event? Do I need the Oracle contract address?
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0answers
64 views

How can I calculate gas price and gas limit programmatically using web3j [duplicate]

I am using following code to deploy my smart contract but now my transaction is taking too much time to mine on my private blockchain. String contractAddress = myContract.deploy(web3j, credentials, ...
2
votes
1answer
166 views

Can I send data (e.g. text) in a Transaction with Web3J?

I need to send a transaction from an account to another one via Web3J that includes not only the value field but also the data field (in particular, I need to send text). Is it possible?
2
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0answers
520 views

JsonParseException while generating java wrapper object with web3j

so a few weeks ago I created a java wrapper object with web3j for a smart contract and was able to work with it with no problems. following exactly what I did a few weeks ago I keep getting a ...
2
votes
2answers
467 views

How do I use filter EVM log events by an indexed field in web3j?

I've looked through the documentation, but there doesn't seem to be this scenario listed. What I want to do is filter the Ethereum event log of a specific contract by an indexed field with Web3j. ...
2
votes
1answer
54 views

Unable to print event without JSONstringify

I am trying to understand the difference among following cases while printing the event: At web3.js listenToEvent: function(){ Contract.deployed().then(function(instance){ instance....
2
votes
1answer
281 views

Why would Ganache behave differently depending on geth, web3j, web3js and web3.py?

I have a smart contract token deployed in a Ganache instance. My dapp written with React and web3.js shows the same 10 accounts for eth.accounts as running the same command in the geth console. If I ...
2
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0answers
2k views

How to integrate smart contracts with android app using web3j

I want to integrate smart contracts with the android app. I wrote a simple smart contract and I want to call that smart contract from android app. For example, in UI part of Android, I put one ...
2
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0answers
397 views

Noob having trouble connecting to the Infura Mainnet

I've been attempting to run a script from my terminal, and have been getting this error: Error: CONNECTION ERROR: Couldn't connect to node https://mainnet.infura.io. I've installed Web3j on my ...
2
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0answers
306 views

web3j make raw call to deployed contract which checks transaction sender

I have deployed contract to rinkeby. Contract method refuses any call except a call from contract owner (aka contract deployer). I can't use Java bindings. I'm trying to use Function API but it ...
2
votes
1answer
3k views

eth_sendRawTransaction:invalid argument 0: json: cannot unmarshal non-string into Go value of type hexutil.Bytes

I call the eth_sign to get signature of RawTransaction, then call eth_sendRawTransaction,but got the error "{"jsonrpc":"2.0","id":1,"error":{"code":-32602,"message":"invalid argument 0: json: ...
2
votes
1answer
374 views

How to do batch transaction in Ethereum using web3j

I want to do batch transaction using the web3j,So how can I do it? Is there any way or feature web3J provides
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5answers
2k views

How to invoke functions of Smart Contract from Android phone?

I deployed a smart contract with solidity along with a GUI by Javascript and HTML. This project works well on my computer. Now I want to invoke functions of Smart Contract from Android phone. Is ...
1
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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 ...
1
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1answer
2k views

Contract.methods.transfer is a not a function error using web3

Running something simple as this: Contract = new web3.eth.Contract(this.contractABI, this.contractAddress) Contract.methods.transfer(toAccount.address, transfferAmount).encodeABI() Gives me ...
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2answers
2k views

Using Web3j to load a smart contract, how do i specify my credentials?

I am using the Web3j library to generate a Java wrapper for my solidity contract, i have already deployed the contract to the blockchain and it has been mined, i now want to load the contract in java ...
1
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3answers
374 views

From a traditional web based application how can I able to call ethereum network node?

Let's say there is a web application running on server 12.34.45.45 ip. Peer A open this web application in his own browser.Now how he will be able to connect a ethereum node where peer B is running....
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2answers
576 views

Offline transaction signing with web3j?

I'd like to generate and sign a transaction offline and then send that transaction with a different account. I've found a few web3js sources and I've read the web3 documentation, but I haven't found ...
1
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1answer
636 views

Error processing transaction request: sender doesn't have enough funds to send tx

In a Java project im testing the web3j library. there I have a method that generate a new account to the blockchain public String url = "http://localhost:7545/"; public Admin admin = Admin.build(new ...
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2answers
165 views

java.lang.RuntimeException: Error processing transaction request: replacement transaction underpriced Output from Server

I am generating transactions in a contract I deployed in the Rinkeby network and the first 300 or 400 transactions had no errors and I received the txHash, but when I continued I got this following ...
1
vote
3answers
858 views

How can i read symbol and name of the token in transaction?

How can i read symbol and name of the token in transaction? I tried to decode input data from transaction, but it wasn't success. the latest Web3j does not have toAscii method in java. Should i use ...
1
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2answers
1k views

Create account with web3j

Im trying to create a account using the web3j library. But i can´t find the method that create accounts. My idea is to make this judgment but not in the Geth console, but yes in the Java application ...
1
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1answer
1k views

How to extract token transfer data from Transaction? (Web3j)

I'm new to ethereum and I would like to confirm a few things about Transaction. I've transferred tokens and I would like to extract method, address transferred to and amount from Transaction(org....
1
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2answers
703 views

What is the “right” way to send Ether to multiple addresses?

I have seen this discussed here but didn't get a satisfactory answer. What is the recommended way to send ether to multiple recipients? One way that I have thought of is follows: Deploy a smart ...
1
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2answers
733 views

Get input data from specific transaction

I have a contract. I store data in ethereum using contract. Is it possible, to work with contract in git-like way. For example, i have a list of previous transaction hashes. Can i fetch data from any ...
1
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1answer
1k views

How to store user private keys and details

I am creating an android DApp and have used go-ethereum to create wallets for users when they create an account. This stores the private key on their device. I want to also keep all of their details ...
1
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1answer
801 views

Event watcher gives [object Object] in Geth console

I compiled a contract source below: pragma solidity ^0.4.0; //////////////////////////////////////////////////////////// // This is an example contract hacked together at a meetup. // It is by far ...
1
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1answer
385 views

Web3 hex conversion - Reading Events Output

Using the following code in Nodejs - Web3 to catch event from Solidity Smart Contract: const cron = require("node-cron"); const Web3 = require("web3"); const ABISimpleStorage = require("./build/...
1
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1answer
279 views

Quorum deploy with Web3j timeout

SCENARIO: I have the following code: final String hostUrl = this.deployerProperties.getProperty("quorum.host.url"); final String hostPort = this.deployerProperties.getProperty("quorum.host.port"); ...
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1answer
46 views

Is it worthwhile to store my supply chain product data on the blockchain using a smart contract? [closed]

I'm currently developing an android app that uses the Web3j framework (Java) to interact with my private Ethereum blockchain (running on Ganache). The app is a supply chain tool that will let users ...
1
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2answers
361 views

Get function returned 2 values in Web3j

I wrapped a smart-contract generated in remix into a Java Project. Im trying to get the two values that return me this function. function getValues(address _a) external returns(bool, uint32) { ...
1
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1answer
835 views

Get the input data of a transaction with web3j

How can I retrieve transaction details (including the input data) from a txHash using Web3j? I tried the following method: public void buscarHhash(Web3j web3, String txHash) throws IOException { ...
1
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1answer
688 views

Web3j how to get event args when parsing logs?

I'm trying to get an event args in web3j version 4.0.1. I use the simple syntax which is explained in the docs. I'm getting the log object but there is no args property or such thing in it. Here is my ...
1
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3answers
839 views

How to check if geth node is running ,from web3j code

I am connecting to Geth using Web3j plugin. web3j = Web3j.build(new HttpService("http://<ip>:<port>")); // defaults to http://localhost:8545/ However, if the Geth node is not started, ...
1
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1answer
649 views

Creating wallets with Web3j

I generate a code to create wallets for a private chain made with ethereum. String password = unlockAccountParameter.getPass(); ECKeyPair keyPair = Keys.createEcKeyPair(); WalletFile ...
1
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1answer
800 views

How get Ethereum address using phrase only in Android

I want to get Etherum address and private key by adding Phrase (or Password) everytime. I tried by following many gihub code.It gives different private key everytime. In Web3j, I found it is based on ...

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