web3j | Lightweight Java and Android library | Blockchain library

 by   web3j Java Version: v4.10.0 License: Non-SPDX

kandi X-RAY | web3j Summary

kandi X-RAY | web3j Summary

web3j is a Java library typically used in Financial Services, Fintech, Blockchain, Ethereum applications. web3j has no vulnerabilities, it has build file available and it has medium support. However web3j has 62 bugs and it has a Non-SPDX License. You can download it from GitHub, GitLab, Maven.

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              web3j has a medium active ecosystem.
              It has 4656 star(s) with 1557 fork(s). There are 224 watchers for this library.
              There were 4 major release(s) in the last 12 months.
              There are 119 open issues and 1004 have been closed. On average issues are closed in 386 days. There are 9 open pull requests and 0 closed requests.
              It has a neutral sentiment in the developer community.
              The latest version of web3j is v4.10.0

            kandi-Quality Quality

              web3j has 62 bugs (2 blocker, 0 critical, 12 major, 48 minor) and 1833 code smells.

            kandi-Security Security

              web3j has no vulnerabilities reported, and its dependent libraries have no vulnerabilities reported.
              web3j code analysis shows 0 unresolved vulnerabilities.
              There are 9 security hotspots that need review.

            kandi-License License

              web3j has a Non-SPDX License.
              Non-SPDX licenses can be open source with a non SPDX compliant license, or non open source licenses, and you need to review them closely before use.

            kandi-Reuse Reuse

              web3j releases are available to install and integrate.
              Deployable package is available in Maven.
              Build file is available. You can build the component from source.
              Installation instructions, examples and code snippets are available.
              web3j saves you 23368 person hours of effort in developing the same functionality from scratch.
              It has 45700 lines of code, 4626 functions and 636 files.
              It has medium code complexity. Code complexity directly impacts maintainability of the code.

            Top functions reviewed by kandi - BETA

            kandi has reviewed web3j and discovered the below as its top functions. This is intended to give you an instant insight into web3j implemented functionality, and help decide if they suit your requirements.
            • Add a constant function .
            • Traverses the data .
            • Make a type reference from a solidity type .
            • Generate static array types .
            • Decodes the input parameters .
            • Create a tuple
            • Compares this tuple with the specified value .
            • Recover from an ECDS signature .
            • This method sends an EIP15 transaction .
            • Decrypts an encrypted key pair .
            Get all kandi verified functions for this library.

            web3j Key Features

            No Key Features are available at this moment for web3j.

            web3j Examples and Code Snippets

            Make a selection which desktop shortcut icons to create in Inno Setup
            Lines of Code : 20dot img1License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            Name: "appdesktopicon"; Description: "Application icon"; \
                GroupDescription: "{cm:AdditionalIcons}"
            Name: "ueficondesktopicon"; Description: "WinUEFI Console icon"; \
                GroupDescription: "{cm:AdditionalIcons}"
            Name: "uefi32de
            TypeError: readline.createInterface is not a function
            Lines of Code : 9dot img2License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            import rl from "readline-promise";
            const readline = rl.default;
            const rlp = readline.createInterface({
                input: process.stdin,
                output: process.stdout,
                terminal: true,
            copy iconCopy
            export default function App() {
              //Our state holding data
              const [state, setState] = useState(false);
              const printState = useRef(null);
              //state update hook
              useEffect(() => {
              }, [state]);
            ProviderError: transaction underpriced on Mumbai Testnet
            Lines of Code : 8dot img4License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            mumbai: {
                  // Infura
                  url: `https://polygon-mumbai.infura.io/v3/${INFURA_API_KEY}`,
                  accounts: [privateKey1],
                  gasPrice: 35000000000,
                  saveDeployments: true,
            "Row is not JSON serializable" error when sending result set to a Flask view
            Lines of Code : 20dot img5License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            results = crsr.execute(query).fetchall()
            print(f"{type(results)} of type {type(results[0])}")
            #  of type 
            json_string = json.dumps(results)
            # TypeError: Object of type Row is not JSON serializable
            results = [tuple
            Thinger.IO client setup for GPRS enabled ESP32 project
            Lines of Code : 83dot img6License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            const char apn[]      = ""; // APN (example: internet.vodafone.pt) use https://wiki.apnchanger.org
            const char gprsUser[] = ""; // GPRS User
            const char gprsPass[] = ""; // GPRS Password
            // SIM card PIN (leave empty, if not defined)
            const c
            what is best ways to set loading/progress in full screen in flutter
            Lines of Code : 71dot img7License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
                class Utils {
                  late BuildContext context;
                // this is where you would do your fullscreen loading
                  Future startLoading() async {
                    return await showDialog(
                      context: context,
            SHA512 hash in Oracle PLSQL vs Node.js
            Lines of Code : 47dot img8License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            const crypto = require('crypto');
            var mystring = 'myteststring';
            var hash = crypto.createHash('sha512').update(mystring).digest('hex');
            JTable with complex formatting
            Javadot img9Lines of Code : 419dot img9License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            package tableTest;
            import java.awt.BorderLayout;
            import java.awt.Color;
            import java.awt.Component;
            import java.awt.Dimension;
            import java.awt.EventQueue;
            import java.awt.FlowLayout;
            import java.awt.Font;
            import java.awt.GridLayout;
            Why my value of array is changing when I'm setting state of other object in react?
            Lines of Code : 49dot img10License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            const [dataToAdd, setDataToAdd] = useState({
              name: "",
              gender: "",
              email: "",
              imgUrl: "",
              website: "",
              skills: "",
            // Use state for skillsAdd array
            const [skillsAdd, setSkillsAdd] = [];
            const handleEnrollClick = () => 

            Community Discussions


            ERC20 transferFrom() private key with web3js and metamask
            Asked 2022-Apr-17 at 03:37

            I used the standard IERC20 to create an ERC20 smart contract.

            I made a gambling game, that if the current user loses, he/she will have to transfer one token to the dealer (also the deployer aka msg.sender of the smart contract).

            With the scenario above, I think that transferFrom("CURRENT_USER_PRIVATEKEY", "DEPLOYER_PUBLICKEY", 1) should be the answer.

            However, with web3js and and metamask, I'm not sure how to get the "CURRENT_USER_PRIVATEKEY", since Metamask won't allow web3js to get the private key. In other StackOverflow posts, I found that we can hardcode this privatekey, but it's not ideal for a system with several users. What should I do to execute this transferFrom() function?

            Here is my smart contract and code for the transaction:



            Answered 2022-Apr-17 at 03:09

            Private key gives you control of that account. So instead of using private key, erc20 implements allowance and approve. I explained them here: what approve and allowance methods are really doing in ERC20 Standard?

            Basically your account address is allowing contract address for a specified token amount to be withdrawn.

            So instead of passing private key, you should be passing the public address

            Source https://stackoverflow.com/questions/71893853


            How to connect Metamask to Web3J (java)
            Asked 2022-Apr-03 at 03:03

            I am trying to connect my Metamask wallet to my Java Spring-Boot backend. I was trying to follow the example here. I am able to autogenerate the nonce and receive the wallet ID without a problem. I am trying to verify the signed nonce from the Wallet on the server to make sure that the sender is indeed who they say they are. However, I am unable to find any documentation on Web3J to do this.

            Is web3j not the right package to use for this? The example shows how to do the verification on NodeJS based on javascript but I don't find any example on how to do this on Java.

            My understanding is that the public key is the wallet ID itself and that the message is the nonce signed by the private key of the wallet which is not shared for obvious reasons. According to this, I would need to "decrypt" the message using the public key and see if the decrypted message is same as the nonce that the backend sent to Metamask to sign. Is this correct?

            Here is my code to create and send the nonce to UI:



            Answered 2022-Apr-03 at 03:03

            I was able to figure this out finally. My initial understanding was incorrect. I was not supposed to attempt to decrypt the message to retrieve the nonce. Rather I needed to use the nonce to see if I can retrieve the public key of the private key used to sign the message and see if that public key retrieved matches the wallet ID.

            The algorithm:
            1. Receive the signed message and the wallet ID from the client
            2. Retrieve the nonce sent to the client with the same wallet ID
            3. Generate the hash of the nonce
            4. Generate the signature data from the message. This basically retrieves the V, R and S and. R and S are the outputs of the ECDSA Signature and V is the Recovery ID.
            5. Using the ECDSA Signature and Hash of the Nonce, generate the possible public Key that was used to sign the message. At max, one will be able to generate 4 possible public keys for this message.
            6. Check if any of the generated keys match public wallet ID that the client sent. If it matches, then we have a positive match. Generate the JWT and respond to the client. If not, we know that the nonce was not signed by the Metamask wallet we expected.
            The Code:

            Here is a sample code for UI (JavaScript and HTML):

            Source https://stackoverflow.com/questions/71630833


            Intellij 2021.3.2, JavaFX Maven project not resolving dependencies correctly
            Asked 2022-Mar-21 at 17:21

            I added a library to my JavaFX projects following these steps:

            1. File --> Project Structure --> Project Settings --> Libraries --> + --> Maven
            2. Insert the Maven coordinates and checked the "Download to projectPath/libs"
            3. In pom.xml added the correct dependecy declaration
            4. In module-info.java added the 'requires module'

            Importing the library to my class seems to work, but after calling a method from the library, it results in a



            Answered 2022-Mar-21 at 17:21

            From the comments, you seem to be using some less common libraries. Sometimes, those kinds of libraries are not updated to be compatible with the Java Platform Module System. I think it is probably safe to assume that unless you know otherwise.

            Defining a non-modular project

            The easiest way to deal with such dependencies is to make your project non-modular: delete the module-info.java.

            But JavaFX itself is only supported as modules. So, even though your project and its dependencies are non-modular, you should still place the JavaFX libraries on the module path.

            Using a JDK which includes JavaFX

            To accomplish such a setup (non-modular application using JavaFX modules), the easiest way is to rely on a JDK or JRE that includes JavaFX modules, for example, the Zulu JDK FX distribution or the Liberica Full JDK distribution. It is important to use the correct distribution as the base JDK distributions for Zulu and Liberica do not include JavaFX.

            Using a base JDK which does not include JavaFX

            With a bit more work, you can use OpenJDK. You can do this by sourcing the JavaFX modules from either the maven repository with a build tool, or a manual download of the modules and SDK from Gluon. In all your build and execution steps, you need to ensure that all of those modules are on the module path and declared to the module system via either VM arguments or a module-info.java.

            Building with Maven

            For a Maven build, you need to add each module to the module path individually, as they are all in separate directories in the local .m2 repository (modern Maven systems and some IDEs, such as Idea, will do that automatically, other IDEs such as VSCode may not).

            Building with the SDK

            Alternately, don't add dependencies on the JavaFX modules via Maven. Instead, download the JavaFX SDK and add the JavaFX modules there via VM arguments --module-path and --add-modules. This process for adding JavaFX modules to OpenJDK is documented in the getting started documentation at openjfx.io.

            A note on openjfx.io Maven archetypes

            Note that the openjfx.io getting started documentation around this mentions maven archetypes. My advice is not to use those as they are really difficult to work with if you try to use them from IDEs. Instead, use the Idea new JavaFX project wizard, either keeping the module-info.java it generates for a modular project or removing it and manually specifying JavaFX module VM arguments for a non-modular project.

            Issues with your project build

            In terms of your actual project, I encountered the same error that duffymo pointed out in the comments:

            I can't resolve all the dependencies for web3jm-evm from Maven Central. It's pulling in a bunch of JARs from org.hyperledger.besu that aren't in Maven Central.

            So I was unable to build or test it.

            Source https://stackoverflow.com/questions/71526616


            Interacting With Contract Web3.js
            Asked 2022-Mar-19 at 17:10

            I have been trying to interact with a contract on the AVAX chain using web3js and it keeps throwing the error, "TypeError: Cannot read properties of undefined (reading 'send')". I cannot figure out why this is happening, as it should be a valid statement. If anyone can help that would be awesome.



            Answered 2022-Mar-19 at 17:10

            The ABI needs to contain just the function and event definitions that are stored in your result property. Without the wrapper object containing status and other properties.

            So in your case

            Source https://stackoverflow.com/questions/71534875


            Web3js fails to import in Vue3 composition api project
            Asked 2022-Mar-14 at 03:36

            I've created a brand new project with npm init vite bar -- --template vue. I've done an npm install web3 and I can see my package-lock.json includes this package. My node_modules directory also includes the web3 modules.

            So then I added this line to main.js:



            Answered 2022-Mar-14 at 03:36
            Option 1: Polyfill Node globals/modules

            Polyfilling the Node globals and modules enables the web3 import to run in the browser:

            1. Install the ESBuild plugins that polyfill Node globals/modules:

            Source https://stackoverflow.com/questions/68975837


            web3js Uniswap handle event log data
            Asked 2022-Mar-07 at 13:02

            I am building a scraper to get all Swap data from Uniswap using web3js. So far I subscribe to the log and filter topics by Swap() event. then I decode the data and get amount0In, amount1In, amount0Out, amount1Out.

            My problem is in the swapExactETHForTokensSupportingFeeOnTransferTokens() function. Normally a swap has token0 in and token1 out, but this function gives me values for 3 of the 4 and I can not seem to understand how to handle that. eventually what I want is to know what they spend, what they got and what I need to update the new reserves of that pair.

            If someone has the understanding of the Uniswap RouterV2 contract swap functions, I would like to get some pointers on how to handle the data to get my calculations right.



            Answered 2022-Mar-07 at 13:02

            I found the solution here ethereum.stackexchange Anyone with the same question gets a very detailed answer there.

            some contracts actually transfers to recipient specified amount of tokens minus 10% (5% tax fee and 5% liquidity fee) 208940457743532637 - 10% = 188046411969179375 and emits Transfer event. Then, PancakePair _swap function emits Swap event with base value of Amount0Out 208940457743532637

            Amount0In is greater than zero because the token contract returns part of tokens as a liquidity pair on Pancake Swap.

            Source https://stackoverflow.com/questions/71376572


            Smart Contract could transfer ether to an address, but the balance of that address does not update
            Asked 2022-Mar-06 at 08:57

            I am trying to get my smart contract to transfer all its balance to another address. The transfer line doesn't throw any errors but the balance of contract does not change afterwards.

            I am using web3js with ganache to test this function:

            My contract:



            Answered 2022-Mar-06 at 08:57
            await contract.methods.pickWinner().call();

            Source https://stackoverflow.com/questions/71368169


            How do I connect to an Infura web socket in Ethers.js?
            Asked 2022-Feb-28 at 05:26

            I know in Web3js you can connect to an Infura web socket like so:



            Answered 2022-Feb-28 at 05:26


            How to get a contract by a transaction uising web3j?
            Asked 2022-Feb-14 at 15:47

            I need to check if a transaction is a ERC721/ERC1155 transaction and fetch information like receiving address, token address, value, etc. If I understand correctly, I have to load a contract for the transaction and check if it inherits ERC165 in order to confirm that it is a ERC721/ERC1155 transaction.

            Problem: I don't understand how I can get a contract having a transaction object. I also haven't found a way to get token address.

            I have an Ethereum node on Infura, I read blocks from there and iterate over transactions. I get a transaction and its receipt. My code looks like this:



            Answered 2022-Feb-14 at 15:47

            You're going in the right direction checking the Transfer() event logs. Even though both ERC20 and ERC721 use the same event signature, the ERC721 (NFT) standard defines the 3rd topic (token ID) as indexed, which stores its value in the set of indexed topics. While the ERC20 defines the 3rd topic (amount) as non-indexed, making the total length of indexed topics set just 2.

            I picked a random transaction that contains event logs of both ERC20 and ERC721 transfers. Looks like the logic behind it is payment in the form of an ERC20 token to mint a new ERC721 token.

            Note: I'm not a Java dev, so I'll use a JS code in my answer that you can hopefully use as a reference to find the correct syntax and methods in the Java implementation of the Web3 library.

            Source https://stackoverflow.com/questions/71038751


            Unable to access process variable in Vue3JS Vite project
            Asked 2022-Feb-14 at 11:06

            I am creating a vue3 application (created with Vite) that interacts with a smart contract written in Solidity and stored on Ropsten. Therefore I am using web3js to interact with my smart contracts and also web3.storage in order to store some images on IPFS. I have a .env file at the root of my project storing my API key for web3.storage :



            Answered 2022-Feb-14 at 11:06

            Community Discussions, Code Snippets contain sources that include Stack Exchange Network


            No vulnerabilities reported

            Install web3j

            The simplest way to start your journey with Web3j is to create a project. We provide this functionality using the [Web3j CLI](http://docs.web3j.io/latest/command_line_tools/). This latter can be installed as follows:.
            Web3j includes integration tests for running against a live Ethereum client. If you do not have a client running, you can exclude their execution as per the below instructions.


            Commercial support and training is available from [web3labs.com](https://www.web3labs.com/web3j-sdk).
            Find more information at:

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