Questions tagged [web3j]

Lightweight Java and Android library for integration with Ethereum clients

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2
votes
2answers
362 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. ...
1
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1answer
34 views

How to decode InputValue of ethereum using java web3j

**I'm trying to decode the inputValue of an transaction using web3j without using any contract abi and wrapper class,Im loading the contract using its contract address ,is there any way/inbuilt ...
1
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4answers
969 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?
0
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1answer
193 views

How can I show on web3j a list of all the instructors added on my blockchain?

I need to show on an html a list of all the instructors that are set up on the list pragma solidity ^0.4.18; contract Owned { address owner; function Owned() public { owner = msg.sender; } ...
2
votes
1answer
249 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 ...
0
votes
1answer
459 views

Failed to connect to localhost/0:0:0:0:0:0:0:1:8545

When I am doing one transaction with the help of Java web3j library, it's not connecting to localhost(my private network). And giving this error. package com.kaushik.blockchain; import java.math....
0
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1answer
27 views

Unable to invoke smart contract function from Web3j contract wrapper

I've been learning about interacting with smart contracts through Android and the Web3j framework but have run into an issue. I'm trying to mint an ERC721 token and send it to an address but it doesn'...
0
votes
1answer
355 views

How to list all recipts in a block using web3js?

I'm trying to list all transactions and their receipts from given block. Transactions get be included in the result of GetBlockByNumber function but I have found no option to include receipts. I can ...
0
votes
0answers
15 views

call array params in web3j

I want to call contract method like this: function airdrop(address source, address[] dests, uint[] values) how can i sendTransaction in web3j by java? i sign like this: Function function = new ...
0
votes
1answer
305 views

Interacting with the smart contract from Java application (We3j)

I have many questions about the workflow ( sequence ) of interacting with the smart contract from Java application, so I will first explain what I have done and then put my questions, and if something ...
1
vote
1answer
31 views

how can i fetch all the tokens from ethereum network to my wallet ?using web3js(nodejs) or web3j(java)?

I'm trying to fetch all the available tokens from ethereum network into my android wallet but could not able to find an suitable solution other than web scrapping
1
vote
1answer
2k views

How to transacting with a smart contract using web3j in Android?

i used web3j to Transacting with a smart contract. this is my Contract function which i want to intertact with. function usersRegister(string _id, string _password){ Equipment e = equipments[msg....
1
vote
1answer
1k views

how to get the status of a transaction which is not mined and pending

I used the following code to send a transaction and get transaction status.However, sometimes the transaction is not minded at all. But the transactionReceipt get the same value "NULL" for both of the ...
0
votes
1answer
286 views

Web3j send ether transaction pending forever

i'm trying to send ether to a smart contract with a specified amount of gas usage, the transaction sending works fine and it propagates to the network but remains pending forever not being executed as ...
0
votes
1answer
345 views

Not able to convert and access Tuples of bytes array and convert to string in Java using web3j

I am new to the development of smart contract using web3j. I am facing issue, while converting Bytes32[] returned from wrapper of contract(.sol) method to array. I have contract as: pragma solidity ...
1
vote
1answer
828 views

iOS: Create Raw Transaction in swift

I'm working on a project related to blockchain and need to figure out, how raw transaction can be possible, I got no reference for this as of now. Can anyone help me? I have tried this lib: https://...
3
votes
1answer
571 views

Recover address from signature using web3j

I have signed a data string using the following code snippet in web3js var data = "hello world"; web3.personal.sign(web3.fromUtf8(data), web3.eth.accounts[0], function(error, result) { if (!...
7
votes
1answer
799 views

Deploy contract in web3j quorum problem

I'm trying to deploy a smart contract (7 nodes sample from Quorum) using web3j. It fails at get() to get the contract wrapper object. If I check the logs, a new transaction will show up, but if I call ...
3
votes
2answers
2k views

Web3j - sending erc20 token

I would like to ask how to correctly send ERC20 Token from a wallet to another wallet , followings are my codes : public static void main(String[] args) throws Exception { Web3j web3 = Web3j....
1
vote
1answer
411 views

How to create wallet with web3j and web3swift like with web3js web3.eth.accounts.create(); function?

With web3js v1.0.0 you can create accounts with web3.eth.accounts.create(); and access the public address and private key with newWallet.address and newWallet.privateKey. How can you do this with ...
3
votes
2answers
2k views

Decoding transaction input data with web3j (Java)

My use case is the following: I would like to have a daemon monitoring how users are interacting with my smart contract. The way I see it is to look at incoming blocks and try to decode input data ...
0
votes
1answer
67 views

How to use web3j to check the balance of an ERC20 custom Token and transfer the token to another wallet?

I'm studying to create wallets using infura, web3j, and android studio. I am using ropsten testnet. I have been able to check the amount of ethereum in my wallet and send ethereum to another account. ...
1
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0answers
18 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 ...
0
votes
2answers
451 views

How to use balanceOf function with Web3j for an android app

I am trying to use the balanceOf function after the generation of our smart contract (pakoin) function wrappers in Java with Web3j. Despite trying different ways, I get plenty of errors and I don't ...
1
vote
1answer
28 views

Using contract to create Child contracts (web3j Java wrapper)

I have a simple Parent contract that creates child contracts and stores their address. contract Parent { address[] public registry; function createChild () public { address newChild =...
0
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1answer
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 ...
1
vote
2answers
1k views

Why is my web3j wrapper failing to generate?

I've created a smart contract in solidity which I've compiled with solc into a .bin & a .abi file. However, when I run the generator on the .abi and .bin files it returns a JSONParseException ...
0
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1answer
41 views

Installing Web3 stuck on fetchMetadata: sill resolveWithNewModule http-https@1.0

I am trying to install web3 for ethereum but it keeps sticking on this fetchMetadata
0
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2answers
266 views

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 ...
0
votes
1answer
494 views

Web3j decode function from TransactionReceipt

I'm connecting to a testnet using a Geth node running version 1.8.8-stable, and also I'm using the web3j lib version 3.4.0. I deployed a Smart Contract and also used the web3j wrapper tools to ...
1
vote
1answer
45 views

raw transactions to send ERC20 token fails on private network(POA)

I am trying to transfer ERC20 tokens on private ethereum network(POA) Transaction flow: raw tx object creation on backend. { "gasLimit": 37000, "gasPrice": 4000000000, "...
0
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1answer
71 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); ...
0
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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 ...
0
votes
0answers
12 views

Web3J Java Android SendAsync Error

I am trying to interact with a method in my smart contract. The method is a simple method where you send a string value to a global variable. I end up using a SendAsync which appears to initially work,...
3
votes
3answers
2k views

How to convert Java String to Bytes32 in Java ? I am using web3j solidity wrapper to interact with Smart contract. I am getting following error:

java.lang.UnsupportedOperationException: Input byte array must be in range 0 < M <= 32 and length must match type I am trying to do as given below. I wanted to add the people but wrapper ...
2
votes
1answer
43 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....
4
votes
1answer
1k views

send() or sendAsync() while using Web3j to call functions

I built a java web application which connects using Web3j with my smart contract deployed on Ropsten Network. My web application provides a control panel to allow the user to send transactions to the ...
1
vote
1answer
41 views

Contract NOT created when using “new” on testnet

I've got a contract which one of his functions creates a new contract in the following manner: (Solidity) function createCarrier() public { P2Carrier newCarrier = new P2Carrier(msg.sender); ...
1
vote
1answer
94 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?
0
votes
1answer
59 views

How estimate GAS from a contract call with Web3j

I'm trying to estimate gas cost of a contract call, i need to send a string to a contract, but i need to see if i overtook the GAS limit. I'm trying like this: Transaction t = Transaction....
0
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1answer
90 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/...
0
votes
1answer
237 views

Load smart contracts in Java application without having the java wrapper class for Web3j (only the address of the contract)

I use web3j to interact with my local Ethereum node (created with geth), and I was wondering how should I handle smart contracts created at runtime. I know that in order to deploy a smart contract ...
0
votes
1answer
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 ...
0
votes
1answer
65 views

getWeb3ClientVersion() returns null

I'm trying to create an android Dapp by using the web3j library. I'm using connection to a local private Ethereum blockchain. When I'm trying to display the Client version it returns null. This is the ...
0
votes
1answer
67 views

java.lang.RuntimeException: Error processing transaction request: insufficient funds for gas * price + value when deploying smart contracts

I am trying to deploy smart contract using web3j. My code is as follows: @RequestMapping("/") public String index() throws Exception { Web3j web3j = Web3j.build(new HttpService("https://...
1
vote
1answer
131 views

web3j event listening on android project

I trying to listen events from smart contract but my code isn't working. what's the problem? Event event = droneChain.UPDATEMISSIONSTATE_EVENT; String encodedEventSignature = EventEncoder.encode(...
0
votes
1answer
60 views

Could someone explain to me the use of the FastRawTransactionManager class?

int pollingInterval = 3000; FastRawTransactionManager fastRawTxMgr = new FastRawTransactionManager(web3j, credentials, new PollingTransactionReceiptProcessor(web3j, pollingInterval, 40)); From what I ...
3
votes
1answer
380 views

Passing Web3 & Contracts Between Components - React Redux & MetaMask

Curious what's the best way to access and pass a web3 contract instance provided by MetaMask between components when using react-redux. At this point, I'm tempted to do the following for both web3 ...
3
votes
1answer
273 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 ...
0
votes
2answers
238 views

Smart Contract with web3j - Stored SHA hash returned is not the same as input

I have a contract that stores sha-256 hashes of documents (stored as bytes32). I also have a method to retrieve a hash that is mapped to a unique id for the document. However, when I retrieve and ...