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Ethereum Api Java

How To Send Ethereum Transactions With Java

How To Send Ethereum Transactions With Java

How to Send Ethereum Transactions With Java How to Send Ethereum Transactions With Java If you're Java developer dipping into the Ethereum blockchain, here's what you need to know about the ins and outs of sending transactions. Aug. 11, 17 Java Zone Build vs Buy a Data Quality Solution: Which is Best for You? Gain insights on a hybrid approach. Download white paper now! After Ive expressed my concerns about the blockchain technology , lets get a bit more practical with the blockchain. In particular, with Ethereum. I needed to send a transaction with Java, so I looked at EthereumJ . You have three options: Full node you enable syncing, which means the whole blockchain gets downloaded. It takes a lot of time, so I abandoned that approach Light node you disable syncing, so you just become part of the network, but dont fetch any parts of the chain. Not entirely sure, but I think this corresponds to the light mode of geth (the Ethereum CLI). You are able to send messages (e.g. transaction messages) to other peers to process and store on the blockchain, but you yourself do not have the blockchain. Offline (no node) just create and sign the transaction, compute its raw representation (in the Ethereum RLP format) and push it to the blockchain via a centralized API, e.g. the etherscan.io API . Etherscan is itself a node on the network and it can perform all of the operations (so it serves as a proxy) Before going further, maybe its worth pointing out a few general properties of the blockchain (the Ethereum one and popular cryptocurrencies at least) it is a distributed database, relying on a peer-to-peer (overlay) network, formed by whoever has a client software running (wallet or otherwise). Transactions are in the form of I (private key owner) want to send this amount to that Continue reading >>

Github - Ethereum/ethereumj: Java Implementation Of The Ethereum Yellowpaper. For Json-rpc And Other Client Features Check Ethereum Harmony

Github - Ethereum/ethereumj: Java Implementation Of The Ethereum Yellowpaper. For Json-rpc And Other Client Features Check Ethereum Harmony

Java implementation of the Ethereum yellowpaper. For JSON-RPC and other client features check Ethereum Harmony If nothing happens, download GitHub Desktop and try again. If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. EthereumJ is a pure-Java implementation of the Ethereum protocol. For high-level information about Ethereum and its goals, visit ethereum.org . The ethereum white paper provides a complete conceptual overview, and the yellow paper provides a formal definition of the protocol. We keep EthereumJ as thin as possible. For JSON-RPC support and other client features check Ethereum Harmony . Adding as a dependency to your Maven project: org.ethereum ethereumj-core 1.6.3-RELEASE repositories { mavenCentral() jcenter() maven { url "} } compile "org.ethereum:ethereumj-core:1.6.+" As a starting point for your own project take a look at git clone ethereumjcp ethereumj-core/src/main/resources/ethereumj.conf ethereumj-core/src/main/resources/user.confvim ethereumj-core/src/main/resources/user.conf # adjust user.conf to your needs./gradlew clean shadowJarjava -jar ethereumj-core/build/libs/ethereumj-core-*-all.jar > git clone cd ethereumj> ./gradlew run [-PmainClass=] ./gradlew run -PmainClass=org.ethereum.samples.BasicSample./gradlew run -PmainClass=org.ethereum.samples.FollowAccount./gradlew run -PmainClass=org.ethereum.samples.PendingStateSample./gradlew run -PmainClass=org.ethereum.samples.PriceFeedSample./gradlew run -PmainClass=org.ethereum.samples.PrivateMinerSample./gradlew run -PmainClass=org.ethereum.samples.TestNetSample./gradlew run -Pmain Continue reading >>

Github - Web3j/web3j: Lightweight Java And Android Library For Integration With Ethereum Clients

Github - Web3j/web3j: Lightweight Java And Android Library For Integration With Ethereum Clients

Commercial support and training is available from blk.io . A web3j sample project is available thatdemonstrates a number of core features of Ethereum with web3j, including: Connecting to a node on the Ethereum network Sending Ether from one address to another Deploying a smart contract to the network Reading a value from the deployed smart contract Updating a value in the deployed smart contract Viewing an event logged by the smart contract Add the relevant dependency to your project: org.web3j core 3.4.0 org.web3j core 3.3.1-android Or use Infura , which provides free clients running in the cloud: Web3j web3 = Web3j.build(new HttpService("For further information refer to Using Infura with web3j Instructions on obtaining Ether to transact on the network can be found in the testnet section of the docs . Web3j web3 = Web3j.build(new HttpService()); // defaults to web3ClientVersion = web3.web3ClientVersion().send();String clientVersion = web3ClientVersion.getWeb3ClientVersion(); To send asynchronous requests using a CompletableFuture (Future on Android): Web3j web3 = Web3j.build(new HttpService()); // defaults to web3ClientVersion = web3.web3ClientVersion().sendAsync().get();String clientVersion = web3ClientVersion.getWeb3ClientVersion(); Web3j web3 = Web3j.build(new HttpService()); // defaults to -> { String clientVersion = x.getWeb3ClientVersion(); ...}); Web3j web3 = Web3jFactory.build(new HttpService()); // defaults to web3j also supports fast inter-process communication (IPC) via file sockets to clients running onthe same host as web3j. To connect simply use the relevant IpcService implementation instead ofHttpService when you create your se Continue reading >>

Integrating The Ethereum Blockchain Into Java Apps

Integrating The Ethereum Blockchain Into Java Apps

Integrating the Ethereum Blockchain into Java Apps How to access a distributed ledger technology blockchain from a Java application using web3j. The Ethereum blockchain is a decentralized platform that is the backbone of a secure, decentralized internet and is driven by the eponymous cryptocurrency Ether. Conor Svensson authored web3j, a lightweight Java library for building Java applications on the Ethereum blockchain. In a first article , which appeared in the Java Magazine, Conor Svensson gives the background of the Ethereum blockchain technology and explains how to create a blockchain that is connected to a Java application. Web3j, a wrapper of client remote procedure calls using JSON, manages the transaction interactions with Ethereum clients. In a second article , he details how to use web3j to query the Ethereum blockchain via its reactive-functional API. He explains how to use RxJavas Observables to add reactive functionality to theblockchain. An Ethereum client like Geth or Parity is the first step to getting you started. Clients will synchronize the Ethereum blockchain with one another and provide a gateway to interact with the blockchain. Ethereum takes care of Ether cryptocurrency payment transactions via the network. With just a few lines of code, you can hook up to the Ethereum blockchain and be notified of new blocks being added to the blockchain and start pulling information out of the blockchain in real time. For code and step by step examples, read the full article here for more information, please visit: web3j project and Conor's blog Continue reading >>

Introduction To Ethereum Smart Contract Clients (web3js Library)

Introduction To Ethereum Smart Contract Clients (web3js Library)

Introduction to Ethereum Smart Contract Clients (Web3js Library) After some discussions around solidity smart contract design and issues in the last two articles ( Here and Here ), we will take a look at how we can integrate smart contracts with enterprise clients applications. There are multiple technologies that can interact with an ethereum node ( ethereum blockchain client ). The basic architecture of the EVM ( ethereum virtual machine ) that runs smart contracts is that all calls to the contract are executed as a transaction where the ether required for a contract method executed is transferred from the calling account address to the contract account address. The contract code resides on the contract address on the blockchain and expects the calls to come in as transactions carrying the method parameter data along with the transaction as input. To enable a standard format for all clients, the method name, and parameters need to be marshaled in a recommended format. Ethereum standard clients expose an interface for making the RPC (Remote Procedure Call) to contract code deployed on the blockchain. This is called the RPC interface serving as an HTTP post requests at default port of 8545 for the go, c++ and parity client. This can usually be customized as a command parameter or a configuration file property: --rpc --rpcaddr --rpcport The RPC format structured on the popular JSON-RPC format. The format is complex especially for marshaling parameter values based on the types. The recommended encoding scheme has to be followed as defined with the correct padding to ensure the EVM is able to decode them. Due to the low-level complexity of the JSON_RPC format, there are a number of wrapper libraries available that simplify the call format. The oldest one is a JavaScr Continue reading >>

Blockchain Developer Api For Bitcoin, Ethereum, Testnet, Litecoin And More | Blockcypher

Blockchain Developer Api For Bitcoin, Ethereum, Testnet, Litecoin And More | Blockcypher

// _ _ // |_) | _ _ | / ._ |_ _ ._// |_) | (_) (_ |< \_ \/ |_) | | (/_ | // / | Continue reading >>

Introduction To Ethereumj

Introduction To Ethereumj

If you're new here, you may want to check out the "API Discoverability with Spring and Spring HATEOAS" live Webinar . Thanks for visiting! I just announced the new Spring 5 modules in REST With Spring: In this article, we take a look at the EthereumJ library that allows us to interact with the Ethereum blockchain, using Java. First, lets just briefly dive into what this technology is all about. Ethereum is acryptocurrencyleveraging a distributed, peer-to-peer, database in the form of a programmableblockchain, the Ethereum Virtual Machine (EVM). Its synchronized and operated through disparate but connectednodes. As of 2017, Nodessynchronize theblockchainthrough consensus, create coins through mining (proof of work), verify transactions, executesmart contracts written in Solidity , and run the EVM. The blockchainis divided intoblockswhich containaccount states(including transactions betweenaccounts) andproof of work. The org.ethereum.facade.Ethereumclass abstracts and unites many packages of EthereumJ into one easy to use interface. Its possible to connect to a node to sync with the overall network and, once connected, we can work with the blockchain. Ethereum ethereum = EthereumFactory.createEthereum(); To connect to the network, we must first connect to a node, i.e.a server running the official client. Nodesare represented by theorg.ethereum.net.rlpx.Node class. The org.ethereum.listener.EthereumListenerAdapter handles blockchain events detected by our client after connection to a nodehas been established successfully. Lets connect to a node on the network. This can be done manually: String ip = "port = 8345;String nodeId = "a4de274d3a159e10c2c9a68c326511236381b84c9ec...";ethereum.connect(ip, port, nodeId); Connecting to the network can also be done automatically using Continue reading >>

Ethereum Developers Apis

Ethereum Developers Apis

[Beta] The Event Log API was designed to provide an alternative to the native eth_getLogs . Below are the list of supported filter parameters: topic0, topic1, topic2, topic3 (32 Bytes per topic) topic0_1_opr (and|or between topic0 & topic1), topic1_2_opr (and|or between topic1 & topic2), topic2_3_opr (and|or between topic2 & topic3), topic0_2_opr (and|or between topic0 & topic2) * fromBlock and toBlock accepts the blocknumber (integer, NOT hex) or 'latest' (earliest & pending is NOT supported yet) * Topic Operator (opr) choices are either 'and' or 'or' and are restricted to the above choices only * fromBlock and toBlock parameters are required * Either the address and/or topic(X) parameters are required, when multiple topic(X) parameters are used the topicX_X_opr (and|or operator) is also required * For performance & security considerations, only the first 1000 results are return. So please narrow down the filter parameters Here are some examples of how this filter maybe used: Get Event Logs from block number 379224 to 'latest' Block, where log address = 0x33990122638b9132ca29c723bdf037f1a891a70c and topic[0] = 0xf63780e752c6a54a94fc52715dbc5518a3b4c3c2833d301a204226548a2a8545 Makes a call or transaction, which won't be added to the blockchain and returns the used gas, which can be used for estimating the used gas [Beta] The WebSocket API allows developers to receive Real-Time notifications about new transactions. The Websocket Demo Page can be useful for seeing how this works. The following policies apply: * To keep the socket connection alive send a {"event":"ping"} every 20 seconds * Maximum number of 30 subscriptions per client * Maximum of 10 concurrent socket connections per/IP * After connecting to the socket you have to subscribe to an event within the next 60 Continue reading >>

Interfacing With Ethereum Smart Contracts Injava

Interfacing With Ethereum Smart Contracts Injava

Interfacing with Ethereum Smart Contracts inJava Since quite a lot of business applications are written in Java, or make use of the JVM for that matter, I believe a primer on how to interface with an Ethereum Smart Contract in Java will prove helpful to the reader. This post requires knowledge of what a Smart Contract is and how to deploy one. To learn why we will probably use a library for interfacing with the Smart Contract a basic understanding of the usage of JSON-RPC in Ethereum is necessary. Lets unveil the supposed magic behind what almost all Ethereum libraries do to interact with the blockchain. Suppose we need to know the gasLimit (maximum amount of computational effort the transactions in a block are allowed to have) of the latest block. Using curl and piping its result to a JSON parser such as jq would, considering we run an Ethereum node on localhost port 8545, look as follows curl --silent -X POST -H "Content-Type: application/json"\ --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["latest", true],"id":1}' localhost:8545 | jq .result.gasLimit The above will yield 0x4c4b3c, which is hex-encoded . Since we probably want to read it as a decimal we can add another pipe and the final command becomes curl --silent -X POST -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["latest", true],"id":1}' localhost:8545\ Leading to the readable result of 4999996. These steps involved are a good showcase on why to introduce an abstraction. Almost all libraries will provide convenient interfaces for these RPC calls. Using the library web3j the command above will translate to web3j.ethGetBlockByNumber(DefaultBlockParameter.valueOf("latest"), Still a lot of steps, and from a software-engineering perspecti Continue reading >>

Eth-contract-api David Roon

Eth-contract-api David Roon

ETH-CONTRACT-API is a java library on top of EthereumJ to make it easier to work with smart contracts from a JVM application (Java, Scala etc ...) The code is open source and accessible here: The library solves 3 main pain points when working with Ethereum. The first goal of ETH-CONTRACT-API is to make integration in your Java application as simple as possible. You can connect to any network declaratively It uses the type system to detect error early It let's you talk to any smart contract the same way you would talk to any other Java Service. All you need to do is create an Interface that represent your smart contract and create a proxy It removes the need to handle the mechanisms of Ethereum. You don't need to know how to define your Nonce You don't need to know how to synchronize and wait for a transaction It is Domain Driven and every Ethereum Value has its own type, you don't work with String and BigInteger but rather with EthValue, EthAccount, EthAddress etc ... Because the integration is made so simple, you can work with a team that is comfortable with your Java environment and understand the Business Logic very well and have a specialized team working on the Smart Contract part of it. Because integration is so easy, ETH-CONTRACT-API is a great tool to create deployment scripts. This means that you can integrate Smart Contract deployment and Bootstrap as part of your workflow and this is as easy as populating a database. It is especially important to test your smart contracts because they are immutable. ETH-CONTRACT-API has an environment to create unit, functional and integration tests as easily as with any other Java system. Testing has to be easy to write in order to invest enough in them Continue reading >>

Bitcoin Price Index Api - Coindesk

Bitcoin Price Index Api - Coindesk

CoinDesk Launches 2017 Year in Review Opinion and Analysis Series CoinDesk provides a simple API to make its Bitcoin Price Index (BPI) data programmatically available to others.You are free to use this API to include our data in any application or website as you see fit, as long as eachpage or app that uses it includes the text Powered by CoinDesk , linking to our price page.CoinDesk data is made available through a number of HTTP resources, and data is returned in JSON format.Please do not abuse our service. On the CoinDesk website, we publish the BPI in USD, EUR, and GBP, calculated every minute, based on criteria as discussed on the CoinDesk BPI page .This same data can be retrieved using the endpoint: {"time":{"updated":"Dec 14, 2017 11:12:00 UTC","updatedISO":"2017-12-14T11:12:00+00:00","updateduk":"Dec 14, 2017 at 11:12 GMT"},"disclaimer":"This data was produced from the CoinDesk Bitcoin Price Index (USD). Non-USD currency data converted using hourly conversion rate from openexchangerates.org","chartName":"Bitcoin","bpi":{"USD":{"code":"USD","symbol":"$","rate":"16,628.4075","description":"United States Dollar","rate_float":16628.4075},"GBP":{"code":"GBP","symbol":"","rate":"12,370.1717","description":"British Pound Sterling","rate_float":12370.1717},"EUR":{"code":"EUR","symbol":"","rate":"14,051.1041","description":"Euro","rate_float":14051.1041}}} We also offer the BPI converted into in any of our supported currencies . This data can be accessed using the endpoint: Where should be replaced by a valid ISO 4217 currency code as per our supported currency list . Sample RequestJSON Response {"time":{"updated":"Sep 18, 2013 17:27:00 UTC","updatedISO":"2013-09-18T17:27:00+00:00"},"disclaimer":"This data was produced from the CoinDesk Bitcoin Price Index. Non-U Continue reading >>

[sold Out] Workshop: Developing Java Applications On The Blockchain With Web3j

[sold Out] Workshop: Developing Java Applications On The Blockchain With Web3j

Grab your Blind Bird Ticket! Lowest prices Save 350 30% group discount Register now EARLY BIRDSave 350 by August 24th!on conference + workshops Register now Grab your Blind Bird Ticket! Lowest prices Save 350 30% group discount Register now EARLY BIRDSave 350 by August 24th!on conference + workshops Register now [Sold out] Workshop: Developing Java applications on the Blockchain with web3j PLEASE NOTE: Workshop will be held in a different Location:Thistle City Barbican Hotel (Central St, Clerkenwell, London) This workshop is for anyone who wants to look beyond the hype and get some hands-on experience developing with blockchain technology.Youll learn how to use and integrate Java applications with the dominant public blockchain Ethereum. Well also touch on the private blockchain technology Quorum. how the dominant public blockchain, Ethereum works what a smart contract is and how you can work with smart contracts from Java web3js reactive API and how it uses the ReactiveX Observables to greatly enhance working with Ethereum how to create and manage tokens via smart contracts on Ethereum how to use the private blockchain technology Quorum with web3j-quorum Continue reading >>

Coinbase Digital Currency Api

Coinbase Digital Currency Api

Coinbase provides a simple and powerful REST API to integrate bitcoin, bitcoin cash, litecoin and ethereum payments into your business or application. This API reference provides information on available endpoints and how to interact with it. To read more about the API, visit our API documentation . Note: If youre still using legacy Coinbase API (v1), you should access relevant API reference , Wallet API and Merchant API documentation. This API supports two modes of authentication: API key - Useful to access your own account OAuth2 (Coinbase Connect) - Used to build applications for Coinbase users curl \ -H "Authorization: Bearer abd90df5f27a7b170cd775abf89d632b350b7c1c9d53e08b340cd9832ce52c2c" OAuth2 is recommended when youre creating an application for others on top of Coinbase platform. This authentication provides a secure and easy to use authentication flow for users. OAuth2 requests must be authenticated with a valid access token passed as bearer token. To use the bearer token, construct a normal HTTPS request and include an Authorization header with the value of Bearer. Signing is not required. API key is recommend if you only need to access your own account. All API key requests must be signed and contain the following headers: CB-ACCESS-SIGN The user generated message signature (see below) CB-ACCESS-TIMESTAMP A timestamp for your request All request bodies should have content type application/json and be valid JSON. The CB-ACCESS-SIGN header is generated by creating a sha256 HMAC using the secret key on the prehash string timestamp + method + requestPath + body (where + represents string concatenation). The timestamp value is the same as the CB-ACCESS-TIMESTAMP header. The body is the request body string or omitted if there is no request body (typically for GE Continue reading >>

How To Send Ethereum Transactions With Java

How To Send Ethereum Transactions With Java

After Ive expressed my concerns about the blockchain technology , lets get a bit more practical with the blockchain. In particular, with Ethereum. I needed to send a transaction with Java, so I looked at EthereumJ . You have three options: Full node you enable syncing, which means the whole blockchain gets downloaded. It takes a lot of time, so I abandoned that approach Light node you disable syncing, so you just become part of the network, but dont fetch any parts of the chain. Not entirely sure, but I think this corresponds to the light mode of geth (the ethereum CLI). You are able to send messages (e.g. transaction messages) to other peers to process and store on the blockchain, but you yourself do not have the blockchain. Offline (no node) just create and sign the transaction, compute its raw representation (in the ethereum RLP format) and push it to the blockchain via a centralized API, e.g. the etherscan.io API . Etherscan is itself a node on the network and it can perform all of the operations (so it serves as a proxy) Before going further, maybe its worth pointing out a few general properties of the blockchain (the ethereum one and popular cryptocurrencies at least) it is a distributed database, relying on a peer-to-peer (overlay) network, formed by whoever has a client software running (wallet or otherwise). Transactions are in the form of I (private key owner) want to send this amount to that address. Transactions can have additional data stored inside them, e.g. representing what they are about. Transactions then get verified by peers (currently using a Proof-of-work based consensus) and get stored on the blockchain, which means every connected peer gets the newly created blocks (each block consisting of multiple transactions). Thats the blockchain in short, Continue reading >>

Interacting With Ethereum Smart Contracts From Android

Interacting With Ethereum Smart Contracts From Android

Interacting with Ethereum Smart Contracts from Android August 23, 2017 by Ondrej Bendo in Android | 6 Comments Usually when you want to interact with smart contracts you need to download the whole ethereum blockchain and keep your local node synchronized. As of writing the blockchain takes up more than 80GB of space on my computer. This might make sense on a desktop computer but is less reasonable on a mobile device. One way to go around this limitation is to use a service like Infura . Infura allows you to connect to a remote ethereum node and execute transactions without having to worry about maintaining and synchronizing your local node. To be able to transact with the smart contract from native Java code I used a library called Web3j . Web3j provides you with utilities for generating smart contract java wrappers and a complete implementation of Ethereums JSON-RPC client API over HTTP and IPC. It provides more features but these were the important ones for this Android Ethereum hello world example. The example smart contract I want to interact with is a Greeter. It stores a greeting message on the blockchainwhich can be read or updated.It looks like this: contract greeter is mortal { /* define variable greeting of the type string */ string greeting; /* this runs when the contract is executed */ function greeter(string _greeting) public { greeting = _greeting; } /* change greeting */ function changeGreeting(string _greeting) public { greeting = _greeting; } /* main function */ function greet() constant returns (string) { return greeting; }} Continue reading >>

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