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Questions tagged [web3j]

Lightweight Java and Android library for integration with Ethereum clients

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2
votes
2answers
348 views

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 ...
2
votes
1answer
895 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 ...
8
votes
2answers
3k views

Web3j listening to events

I'm tinkering with web3j and most of the things that I want to do succeed, however I seem to not be able to listen to events. I've extended the ballot.sol contract you get with remix by adding an ...
7
votes
2answers
7k views

How to create accounts and also retrieving the ether balance with web3j in a java file?

I do not see anything in creating accounts and retrieving ether balance in web3j's documentation, I wonder if it is possible.
2
votes
2answers
5k views

Generate private key and address using web3j

How can i generate private key and address using web3j instead of creating keystore json file
8
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5answers
15k views

why did it returned null after call miner.start()

> miner.start() > null before it , I had created a account like this . user1 = eth.accounts[0] "0xb62f0bae52d153365661c4e23ab1d594484e9bef"
0
votes
4answers
866 views

web3j-android error: static interface method calls are not supported at language level 1.7

I get this error static interface method calls are not supported at language level 1.7 when having Web3j web3j = Web3j.build(new HttpService(url)); documentation here says for Android you should ...
5
votes
3answers
2k views

A problem with filters and events (web3j/TestRPC). SOS! ;)

Help me, please, with this little simple task! I cannot solve this problem for several days. SOS! ;) I'm trying to write a program for filtering events via web3j. I copied to start (for the test) from ...
1
vote
5answers
1k 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 ...
3
votes
2answers
5k views

Send Custom ERC20 Tokens from one Address to another

How to send custom ERC20 tokens from one wallet to another, if i want to send EBTC/ECASH custom ERC20 tokens. I wrote a method that can send the ether from one account to another, how could i do the ...
2
votes
1answer
2k views

Web3j: “Intrinsic gas too low” error when deploying contract in Ethereum from Java

I am a new to Ethereum and Blockchain, I have been trying execution of Contracts using Metamask and Remix using Chrome browser for sometime. I am trying to deploy the same contract from Java using ...
9
votes
3answers
3k views

Deploy contract on EthereumJS TestRPC

Following https://medium.com/@mvmurthy/full-stack-hello-world-voting-ethereum-dapp-tutorial-part-1-40d2d0d807c2 I've tried to create an instance of a contract using: VotingContract = web3.eth....
7
votes
1answer
783 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 ...
5
votes
1answer
3k views

Convert String to Bytes32 in web3j?

public String solFunction(String str) { byte[] byteValue = DatatypeConverter.parseHexBinary(str); Bytes32 strInBytes = new Bytes32(byteValue); try { Uint256 value = contract....
1
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2answers
2k views

How to make transaction using private key and address using web3j

I have a private key and address . Is it possible to make transaction with these parameter using web3j.
5
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1answer
2k views

Solidity ecrecover and web3j Sign.signMessage() are not compatible, is it?

Using Web3j to sign and verify a message is fine but when I use the signature generated by Web3j to verify using ecrecover in solidity it doesnot seem to work correctly. The signer address is ...
3
votes
2answers
637 views

How to catch solidity contract revert message using web3j

Is there any way to catch solidity revert message like Remix Javascript VM in web3j Revert message(remix) transact to Erecruitment.issueNewAdmitCard errored: VM error: revert. revert The ...
3
votes
1answer
411 views

Ethereum - how to get merkle proof

I'm trying to figure out the check of existence and the immutability of the transaction in the Ethereum block, but I do not know how to get mercle branch. With the help of web3j I can get the block ...
3
votes
1answer
3k views

web3.eth.getBalance returns me the strange values ?

i am trying to get the balance of a wallet, the method is working but the returned result is a json object - { c:(2) [484895,26495000000000],e:19, s: 1}. In which the value - 484895 corresponds to ...
2
votes
1answer
1k views

Function of smart contract returns 0 from Web3j

please help me in this problem. I am successful to compile and deploy my smart contract using web3j on testrpc. But When I call the function that returns uint in this contract from web3j, I always ...
1
vote
1answer
593 views

problem when deploy smart contract in Quorum using web3j

I'm using web3J when i try to deploy contract i get Error processing transaction request: Non-200 status code: &{Status:400 Bad Request StatusCode:400 Proto:HTTP/1.1 ProtoMajor:1 ProtoMinor:1 ...
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 ...
1
vote
1answer
688 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
vote
2answers
2k views

Creating an account using web3js or web3j

I am trying to create account on ethereum private network using web3js from front end. I have written the below lines in my js file. The createAccount() gets called from an HTML page web3 = new Web3(...
1
vote
1answer
274 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 ...
0
votes
1answer
59 views

How to return the change to the sender?

In this answer, @pabloruiz55 provides the following code for sending ether. SmartContract.sol function transferToOwner() payable returns (bool) { //Sender should forward at least 1 ether. ...
0
votes
1answer
90 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 ...
0
votes
2answers
611 views

A bit confused. How do I send ether using Web3j to an address (Android)

EDIT: I am using android platform I think I'm a bit confused conceptually. I would appreciate it if someone could answer these few questions for me as I'm trying to make an app so that I can be ...