Questions tagged [web3j]

Lightweight Java and Android library for integration with Ethereum clients

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1answer
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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 ...
0
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1answer
916 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
1k 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, ...
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1answer
475 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 ...
1
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2answers
475 views

web3j: EthSendTransaction.sendTransaction() is throwing "Error processing transaction request: Invalid params: invalid format"

I am trying to send a transaction to an address: 0xDD210......... using the EthSendTransaction.sendTransaction() method from the org.web3j.protocol.core.methods.response.EthSendTransaction library. ...
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3answers
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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 ...
1
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1answer
212 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(...
2
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1answer
507 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; ...
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2answers
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how to get latest block number using web3j java APIs

I ask the network for current balance of the address i want to keep track. after that i want to detect/listen incoming deposits starting at the latest block number at the start of my program/server. ...
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3answers
2k 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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1answer
796 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 ...
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2answers
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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 ...
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1answer
730 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'...
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1answer
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retry mechanism for transactions in web3j

In my Java-web-application I have (with one click) to send about 120 transactions after each other from the same address to the same smartcontract. My question: is there any java libraries or ...
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1answer
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Need help integrating ERC20 on Exchange [closed]

Pardon my ignorance, as I have very less knowledge of ERC20 and Ethereum. I am part of an exchange development and we have successfully integrated coins but when it came to ERC20 tokens, we are ...
0
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1answer
385 views

Converting int to default block parameter

I am using Infura and web3j to query the Ethereum blockchain. My aim is to get information about certain blocks so i'm using the function web3.eth.getBlockByNumber, however it gives me incompatible ...
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1answer
445 views

Send function transaction to existing smart contract using web3j

I've been exploring web3j and got the credentials working so I'm able to send transactions from an ethereum address. Now I want to send a transaction to an already existing smart contract and use a ...
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0answers
346 views

How to encode tuple as input parameter to function using web3j

I am attempting to call a solidity function that looks something like the following: function fillOrder( Order memory order, uint256 takerAssetFillAmount, bytes memory signature ) Using ...
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1answer
890 views

Port number for connecting web3 to mainnet using Geth

I am trying to connect web3j object to the mainnet using geth. I can't use infura because i am working with replay transaction observable function which doesn't work with infura. To connect with the ...
2
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1answer
448 views

Input byte array must be in range 0 < M <= 32 and length must match type-web3j

I have created an api to addCandidates. But when i run the api i get error: Input byte array must be in range 0 < M <= 32 and length must match type My codesnippet for addCandidates is: @...
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1answer
99 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://...
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1answer
143 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/...
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1answer
478 views

Compatibility between Solidity language and Web3j library

What is the compatibility between solidity and web3j. I don't find any resource about it. Suppose if I generate my java wrapper class of smart contract written in Solidity ^0.4.17 version and taking ...
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1answer
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how to use Web3j library for android

hi guys i am confuse about the web3j library for android i search about this but i did not get any materiel about this (https://github.com/web3j/web3j). this is lib for using ether node on java and ...
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2answers
843 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 ...
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2answers
365 views

personalUnlockAccount.accountUnlocked() giving NullPointerException even if correct passphrase has been inserted

When I trying to unlock the account with personalUnlockAccount.accountUnlocked() method of PersonalUnlockAccount class of web3j library, it's giving NullPointerException even if I am entering right ...
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1answer
159 views

Value returned by a getter from smart contract instead of uint : org.web3j.protocol.core.RemoteCall@5104cf00 - spring boot - web3j

pragma solidity ^0.4.18; contract MyDeal { /// The seller's address address public owner; /// The buyer's address part on this contract address public buyerAddr; /// The Buyer struct ...
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2answers
900 views

I am using web3j and geth. How to create default accounts with some ether allocation to it?

I need a default account with huge ether allocation. This I need to set up manually in genesis.json Hereafter,all accounts need to be created dynamically in java, and they should also be given some ...
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3answers
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How to use mnemonic to recovery my ethereum wallet

I use web3j to create my ethereum wallet.the Code just like down import org.web3j.crypto.Bip39Wallet; import org.web3j.crypto.Credentials; import org.web3j.crypto.ECKeyPair; import org.web3j.crypto....
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0answers
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Web3j no transaction pooling with REST

I have setup an application with jhisper gateway with one microservice in REST linked to Web3j. Idea is when you store an object in the database, you notarize it in a private ethereum blockchain. So, ...
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0answers
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necessity of mining while doing transaction [duplicate]

While doing any transaction in private network, is it necessary for one node to keep on mining?. I was trying to implement to deploy smart contract and transact in ethereum private network with the ...
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1answer
766 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....
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0answers
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Web3J - Creation of Light Wallet takes too long

I am creating the wallet in my Android app, using the library Web3j: https://web3j.io/ See the code: String seed = UUID.randomUUID().toString(); ECKeyPair exKey = Keys.createEcKeyPair(); WalletFile ...
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1answer
457 views

How to generate ERC-20/xxx token addresses?

How to generate ERC-20/xxx token addresses, from which I can receive/send corresponding tokens? How can I do this using web3j?
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1answer
54 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); ...
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1answer
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How do I get the raw private key from a WalletFile object?

How can I get the raw private key from a WalletFile object? Here is how I am creating the wallet. String seed = UUID.randomUUID().toString(); ECKeyPair exKey = Keys.createEcKeyPair(); BigInteger ...
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1answer
453 views

How to get contract creator using web3j?

How can I get the address of the creator of a contract using web3j? Is it possible to get the first transaction of a contract and assume that the "from" field is the contract creator? If so, how can I ...
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1answer
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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 (!...
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2answers
377 views

web3j transactions with value

I'm using web3j to analyze transactions. How can I get transactions of a specific contract (assuming I got it's address) in some time frame (or blocks interval) and how can I know if ERC20 tokens were ...
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1answer
856 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 ...
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0answers
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Filtering blocks on basis of transaction logs in web3j

I want to filter blocks on the basis of a log present inside transactions. How can I do that? I don't have any contract address and want to filter all the blocks generated by all the contracts. ...
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1answer
489 views

java.lang.RuntimeException: Error processing transaction request: insufficient funds for gas * price + value when invoking smart contract function

using web3j for loading a contract which is deployed on the private network following this tutorial https://web3j.readthedocs.io/en/latest/smart_contracts.html#constant-methods smart contract ...
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1answer
947 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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1answer
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how to know smart contract gas price and gas limit when deploying the contract using web3j

I am new to smart contracts and ethereum I am using web3j to deploy contracts on the private network Following this as a guide https://github.com/web3j/web3j In the below section of code, it asks ...
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1answer
715 views

Getting contract binary using web3j

I'm using web3J library in my java app. I got an address of a deployed contract and would like to get it's binary or abi from the blockchain using my java app, how can I do that?
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0answers
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Storing generated accounts. Security

I originally built a system that had a front end where users simply entered some details and a password which then generated them a wallet and emailed it to them. My aim was that the user could then ...
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2answers
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Getting "insufficient funds for gas * price + value" with geth on Ropsten no matter what

I'm having geth 1.7.3 (tried 1.8.x too) running in docker container: --verbosity 4 -rpc --nousb --ipcdisable --rpcaddr "0.0.0.0" --rpccorsdomain "*" --syncmode "fast" --rpcapi="db,personal,eth,net,...
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1answer
832 views

Web3j directly gets string from contract by eth_call

I just have a simple solidity contract: pragma solidity ^0.4.19; contract SampleContract { string value; function SampleContract() public { value = "hello world"; } ...
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1answer
1k views

Cannot send ERC20 tokens because user has no ethereum

I have 1 wallet server but have many account address for each user, so when user want to transfer erc-20 token say OMG to another address(user) in the same wallet server, the system said can not ...
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2answers
3k 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 ...

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