Questions tagged [web3j]

Lightweight Java and Android library for integration with Ethereum clients

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Send ether from one wallet to another

I have two metamask accounts and what I want to do is send ether between those accounts. For the interaction between those accounts, use infura, I give the address of both accounts but in the end the ...
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invalid opcode “0x1c” during smart contract method execution

I have written a smart contract to test event from java project using web3j I have prepared the web3j wrapper java class using solc compiler version "0.5.7+commit.6da8b019.Linux.g++" I am using a ...
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Invalid OPCode on passing address parameter through Java wrapper on smart contract using Ganache

I have been facing this issue for some time and I realized there must be a problem with Ganache or maybe someone has any idea why it doesn't work. I have created a very simple contract as below, it ...
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247 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 ...
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What's problem about “gas required exceeds allowance or always failing transaction”

I translate smart contract into Java with solc and web3j, but I meet the probelm "gas required exceeds allowance or always failing transaction". This is my smart contract. It is work when I use ...
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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 ...
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156 views

Unable to make a transaction with Data using Java api ethSendRawTransaction

I am trying to make a transaction between two different accounts using Java. It works perfectly fine as long as I am not using "Data" parameter. My intent is not to call a smart contract but to make ...
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1answer
203 views

web3j.ethCall returns null when retrieven contract variable

Environment: Geth node Geth/v1.9.0-unstable/windows-amd64/go1.12 Commands used to start the node to mine: geth --datadir "." --networkid 101 -verbosity 6 --port 30301 --rpcport 8101 --nodiscover -...
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ERC-20 TransferFrom function exceeds GasLimit calling from other conract

I have the following error. Imagine that I have contract A, B(ERC20 implementation contract), C, D and E. They are inherit in that order. Testing the functionallity works fine in remix. But when I try ...
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39 views

Catching FilterException web3j

I'm using web3j to subscribe for transactions: Flowable<Transaction> observable = web3.replayPastAndFutureTransactionsFlowable(startBlockParameter); Scheduler ...
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2answers
179 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) { ...
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1answer
290 views

org.web3j.tx.exceptions.ContractCallException: Empty value (0x) returned from contract

Problem: org.web3j.tx.exceptions.ContractCallException: Empty value (0x) returned from contract The code is as follows.... My java: String owner = managedWalletLookup.getOwner(contractAddress).send(...
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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....
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116 views

how to find if a Tx hash is in pending state in ethereum mainnet after web3j fastTxMgr timeout

I am using QueuingTransactionReceiptProcessor() with callback accept(). DEFAULT_POLLING_ATTEMPTS_PER_TX_HASH is 10 and POLLING_FREQUENCY is 15000. That gives nearly 3 min wait for network to ...
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Build web3j to connect to blockchain [duplicate]

Can't connect to the Ethereum blockchain with web3j 4 for Android Kotlin. Worked in the previous version of web3j. fun web3(): Web3j = Web3jFactory.build(HttpService("http://192.168.38.148:7545")) ...
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Subscribe to changes in contract balance (Web3j)

Using web3j I would like to subscribe to changes in a contract balance i.e deposits and withdraws. I would like to base this subscription over transactions (and not events) since the contract does ...
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251 views

Quorum node address

In the Node class of the Quorum Web3j. The String address what is? package org.web3j.quorum; import java.util.List; /** * Quorum node configuration class. */ public class Node { private final ...
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Error: replacement transaction underpriced web 3j

I am registering a batch of 500 transactions in a java application with web3j and after a while it gives me this error: java.lang.RuntimeException: Error processing transaction request: replacement ...
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1answer
243 views

Where is the ethLogObservable method in Web3j?

I can´t find where is the Web3j ethLogObservable method. I can´t find in GitHub repo
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166 views

Recover solidity funcion event in web3j

EthFilter filter = new EthFilter(DefaultBlockParameterName.EARLIEST, DefaultBlockParameterName.LATEST, userContract.getContractAddress().substring(2)); I am trying to recover the event response that ...
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361 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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478 views

How to change the nonce between transactions in web3j?

I have this line of code where it registers a transaction in blockchain. And I wanted to know how I can make the nonce different between the transactions? txhash = careercertificate ....
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164 views

Error generating new account with Web3j

Im using the Web3j library to make transactions with my blockchain (Ganache). I have a method that instantiate a Web3j object and im trying to generate a new account with the given String url = "...
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2answers
83 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 ...
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167 views

Calling a contract's function with input parameters and passing ether from Geth/Web3

I have deployed a smart contract which basically splits the incoming funds to the specified addresses based on the entered ratio parameter. Please find the code below: pragma solidity ^0.4.23; ...
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Quorum & web3j: Transaction has failed with status: 0x0. Gas used: 0. (not-enough gas?)

I'm doing some play & test with Quorum. I'm using example 7nodes with docker. The network is up and my simple smart contract is deployed with a set and a get function. When I call the set function ...
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318 views

ethLogFlowable: how to get event args?

I am using ethLogFlowable to subscribe to an event and read the args of the event, in my case an address and a uint256 value. I have followed this answer stackExchangeLink, but I am always getting ...
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1answer
249 views

What does the get Status () method return with a pending state transaction?

If a transaction has a successful state it returns 0x1 but if the transaction has a failed state it returns 0x0. My questions is, what to return when the transaction has a pending status? public ...
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188 views

Can anyone help me to access my eth account in metamask using infura in android

My question is about accessing my eth account in metamask using infura in android
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282 views

How to Serialize/Deserialize array of bytes?

I'm writing a smart contract and inevitably need to have arrays of bytes as input and output of functions. In remix arrays work just fine but with web3j and web3js there are several issues with arrays ...
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201 views

How to apply EthFilter to specific address?

In web3.js, we can apply event filter something like below: this.event = this.Contract.events.MyEvent({ filter: { address: "0xAccountAddress" }, }) In Web3J, it is translated to EthFilter ...
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659 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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How to do decoding with web3j?

I am looking for how to decode the input data of a transaction and what I have obtained up to now is in utf-8 and it gives me this data: "Ã;` Q ò  à                          ...
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1answer
115 views

Anyone with knowledge in org.web3j.abi.Type Decoder?

I am trying to decode a String with this code that I found but I have not been able to do it. String to = inputdata.substring(10, 74); String value = inputdata.substring(74, 138); Method refMethod = ...
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How to decode the input data in java?

I receive the input data as the image shows. And when I try to decode it with the method: String inputdata = null; Optional<Transaction> tx = web3.ethGetTransactionByHash(txHash).send()....
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1answer
454 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 { ...
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620 views

How can I get the TxReceipt of a transaction with web3j?

How can I get the status of a transaction through the TxHash with web3j. I tried it like this: public int getEstado(String trx) { try { JSONObject json = readJsonFromUrl("https://api....
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1answer
98 views

How does Ethereum Smart Contract work on Mobile Client

I want to deploy a smart contract on server and interact with it using mobile client. I'm not familiar with how does that work but after some research, I found something like below: If we compare ...
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1answer
78 views

How to get the txHash of a transaction?

I have this method where I make a transaction to the network rinkeby, but to know how I can get the hash of the transaction made. I am using java with web3j, in addition to using infura to connect to ...
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2answers
213 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
316 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 ...
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742 views

How to install web3j command line to generate smart contract wrapper

I am trying to generate a simple smart contract wrapper using solc and web3j in ubuntu. I have downloaded the source as defined in https://docs.web3j.io/command_line.html Release package can be ...
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transactionHash returned null sometimes when trying to transfer funds using web3j (random behaviour)

I am transferring funds using web3j. However, I was getting transactionHash as null. I checked various posts and found that this issue exist when gas price or gas is bad. I increased both the values, ...
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1answer
271 views

how to use web3j over infura to find exact gas price used for a successful transaction

my goal is to compute the cost of gas for a successful tx. I get a callback when a transaction succeeds and i retrieve gasUsed with transactionReceipt.getGasUsed(). Now I need to know the exact gas ...
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1answer
495 views

how to deploy a smart contract in ethereum using web3j

i am following this tutorial tutorial under the section Working with smart contracts with Java smart contract wrappers i followed the same steps but i am getting RunTimeException here is the full ...
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[RuntimeException: java.lang.NoSuchMethodException: SmartContract using web3j

I am following this tutorial for deployment of contract https://www.youtube.com/watch?v=ibAh04Csp0M&index=33&list=PL16WqdAj66SCOdL6XIFbke-XQg2GW_Avg but i am getting [RuntimeException: java....
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3answers
63 views

Transfer ETH using third party

I want to transfer ETH from an individual address to another address. So is there any API provider who can send ETH from single Address to another address. Also If I setup Web3 in windows machine ...
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1answer
363 views

Not able to decode the input data from transaction using web3j

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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1answer
381 views

java.lang.ClassCastException: org.bouncycastle to error while creating wallet using web3j

I am using web3j to create account. String walletFileName = WalletUtils.generateFullNewWalletFile(" <password>",new File("some/path")); But getting this error: java.lang.ClassCastException: ...
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3answers
537 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, ...