14
votes
Accepted
Generate private key and address using web3j
Below is my approach, verified by importing the result privatekey into MetaMask and get the same address as expected.
private static JSONObject process(String seed){
JSONObject processJson ...
- 381
12
votes
Accepted
How to create accounts and also retrieving the ether balance with web3j in a java file?
The "ethGetBalance" method will return the balance of any given account. Pls see example below:
// connect to node
Web3j web3 = Web3j.build(new HttpService()); // defaults to http://localhost:8545/
...
- 136
11
votes
why did it returned null after call miner.start()
Recently, there are so many people confused about miner.start(1) returning null, but it's actually not a problem, just a reasonable return value misunderstanding. If you aren't sure that your node is ...
- 2,161
11
votes
Accepted
How to view custom token balance in ether wallet using web3
Here is my suggestions:
ERC20 token balance
Just to clarify, all ERC20 tokens have the same set of methods (ERC20 protocol). Now, there are two ways to accomplish your task:
use ERC20 balanceOf(...
- 871
10
votes
how to get latest block number using web3j java APIs
This is the easiest way
Web3j web3j = Web3j.build(new HttpService("https://rinkeby.infura.io/v3/......."));
Block block = web3j.ethGetBlockByNumber(DefaultBlockParameterName.LATEST, false).send()....
- 3,257
10
votes
Accepted
How to create a RawTransaction for contract interaction Web3j
Let's take for example the following simple storage contract:
pragma solidity ^0.5.6;
contract SimpleStorage {
uint storedData;
function set(uint x) public {
storedData = x;
}
...
- 7,247
8
votes
Web3j listening to events
I know this question is old, but providing an answer here as I came across this issue and couldn't find a solution elsewhere...
This appears to be a bug in Web3j that occurs when you pass in the ...
- 670
8
votes
Accepted
How to Query the state of a smart contract using web3j in Android?
Love that your using Web3J, I think with a little practice you will find that it's a great API for dealing with Ethereum :-) So regarding your question there are two things:
I think your problem is ...
- 687
8
votes
Accepted
Convert String to Bytes32 in web3j?
SOLVED!!! LONG/Detailed METHOD!!! (Shorter Version at bottom)
The main problem was Bytes32(byte[]) only supports 32 length byte[].
Also keep in mind Numeric.hexStringToByteArray(strValueInHex) ...
- 151
7
votes
send() or sendAsync() while using Web3j to call functions
You can send and confirm transaction without waiting using CompletableFuture and callback function.
rc-> Instance that calls contract function through remote call.
CompletableFuture<...
7
votes
Accepted
How to change the nonce between transactions in web3j?
Under the hood, the Web3J SmartContract Java Wrapper calculates the nonce by getting the number of transactions getTransactionCount for the account (credential).
EthGetTransactionCount ...
- 7,247
7
votes
Accepted
How to point web3j to other networks such as BSC?
If you are using the smart contact wrapper then you usually need to give one of the available transaction managers as a parameter and then give the chain Id when you initialize it
Web3j web3 = Web3j....
- 3,257
6
votes
why did it returned null after call miner.start()
try setting miner.setEtherbase(eth.coinbase)
or step by step:
start Mist browser (let the node synchronize completely)
open console and type: geth attach
miner.setEtherbase(eth.accounts[0])
miner....
- 194
6
votes
Accepted
Convert ethereum balance getting in biginteger to ether
@Luiz Soares Thank you for giving me the clue of the value being in WEI but solution provided didn't worked me.After some digging the documentation again got the solution
Convert.fromWei(...
- 133
6
votes
Accepted
How could I send transactions continuously by Web3j generated wrapper
I found the solution, please refer, #296
Use FastRawTransactionManager to speed up your transactions. Use RawTransactionManager to shorten the polling interval. If you need both, use the following ...
- 243
6
votes
Accepted
How to get public key from private key in Web3j
Yes, you can do it using following code
import org.web3j.crypto.Credentials;
import org.web3j.crypto.ECKeyPair;
public static String getPublicKeyInHex(String privateKeyInHex) {
BigInteger ...
- 381
6
votes
How to catch solidity contract revert message using web3j (Java)
In solidity 0.4.22 the require and revert reason were added. As can be seen here, they are abi-encoded as if it were a call to a function "Error(string)".
You'll need to make an eth_call to your ...
- 311
5
votes
Accepted
Solidity ecrecover and web3j Sign.signMessage() are not compatible, is it?
The problem was actually double hashing.
Looking at the Web3j's signMessage() method
Sign.SignatureData sig =Sign.signMessage(messageBytes, ecKeyPair);
and signedMessageToKey() method
String pubKey ...
- 131
5
votes
Accepted
web3.eth.getBalance returns me the strange values ?
It is the BigNumber representation of the wallet balance that is output by your script.
Indeed, BigNumbers need to be transformed through toString(int) or toNumber() in order to become compatible ...
- 66
5
votes
How to get public key from private key in Web3j
I posted my own answer here in case someone else has the question. Web3j provides a ECKeyPair as util to process key and address conversion. Please see codes below:
String privateKey = "{your ...
- 700
5
votes
How to use mnemonic to recovery my ethereum wallet
For Bip44 wallets Web3j will use the derivation path m/44/60'/0'/0. The more commonly used path is m/44/60'/0'/0/0 (with an extra /0).
The following code will derive the correct address given a valid ...
- 30.3k
5
votes
Accepted
Web3j how to get event args when parsing logs?
For the following event:
event MyEvent(address indexed _arg1, bytes32 indexed _arg2, uint8 _arg3);
You can extract the event arguments from the log like this
// Event definition
public static ...
- 7,247
5
votes
Accepted
How can I get the TxReceipt of a transaction with web3j?
There's the Transactions page in the Web3j docs that mentions transaction receipts a few times, and I browsed through some of the autocompletes in IntelliJ. It looks like you can do the following, ...
- 2,147
5
votes
Accepted
Contract.methods.transfer is a not a function error using web3
If you are using web3 v0.x then you can send transaction by following:
// creation of contract object
var MyContract = web3.eth.contract(abi);
// initiate contract for an address
var ...
- 224
5
votes
Accepted
How to apply EthFilter to specific address?
OK, let's say you have a smart contract deployed on the address CONTRACT_ADDRESS which can trigger different type of events
Event definitions:
event GameStarted(bytes32 indexed gameId, address ...
- 7,247
5
votes
Accepted
Offline transaction signing with web3j?
I think something like this should work
// Create the Transaction
RawTransaction rawTransaction = RawTransaction.createEtherTransaction(<nonce>, <gasPrice>,
<gasLimit>, <...
- 3,257
4
votes
Accepted
How to store user private keys and details
If you store keys and password anywhere else than on the users device then you are back to square one, should stop right here, go back to using a traditional webservice and payment integration using ...
- 8,784
4
votes
Accepted
Using Web3j to load a smart contract, how do i specify my credentials?
To generate the Credentials if you have a plain public key and private key, you need to convert them in to the hex representation and then pass them in to the constructor for Credentials
String ...
- 151
4
votes
How fetch transaction history for account quickly using Web3j?
There is no workaround besides of the links you´ve posted. It will depend of your CPU power, network and database. I believe they (etherscan team) gets data from the blockchain and stores in an ...
- 1,054
4
votes
How to view custom token balance in ether wallet using web3
Web3 has been updated since @Vanja Dev's answer
var tokenInst = new web3.eth.Contract(tokenABI,tokenAddress);
tokenInst.methods.balanceOf('0x260c25f991171850f48889eb9d8aF11998D20c30').call()....
- 140
Only top scored, non community-wiki answers of a minimum length are eligible