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What this article shares to you is about how to build the web3j ethernet development environment. The editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

Web3j is a lightweight ethernet square Java development kit that can be used in desktop, server or mobile applications to access ethernet block chain smart contracts. The web3j development environment includes nodes for development and testing and the web3j development stack. This article describes how to build a web3j development environment on your own machine.

The construction of the web3j development environment is divided into the following steps:

Install the ethernet development node: Ganache

Install the Java development kit: OpenJDK

Install the Java project build tool: Gradle

Install smart contract command line tools: Solc and Web3j

Web3j application development and debugging: hello web3j

1. Install the ethernet square development node

Web3j accesses the node block chain through the standard Ethernet Square RPC interface, so it can dock with various node software such as geth or parity. However, usually in the development process, we use the development node Ganache, which does not need to synchronize block data from the network, so it is very suitable for rapid verification in the development process.

Install ganache using npm:

~ $npm install-g ganache-cli

After installation, you can start the node by executing it directly:

~ $ganache-cli2. Install JDK

You can install jdk for either openjdk or oracle. Under ubuntu, you can install directly using apt:

~ $sudo apt-get install openjdk-8-jdk

After the installation is complete, verify that the installation is successful using the following command:

~ $java-version3. Install Gradle

Web3j supports maven or gradle as a project build tool. This paper takes gradle as an example to illustrate.

Download the latest version of the precompiled package from the gradle official website, then decompress and configure the environment variables:

~ $wget https://gradle.org/next-steps/?version=5.1&format=bin~$ mkdir / opt/gradle~$ unzip-d / opt/gradle gradle-5.1-bin.zip~$ echo PATH=/opt/gradle/bin:$PATH > > .bashrc ~ $source .bashrc

Verify the installation:

~ $gradle-version4. Install intelligent contract development tools

The development tools for smart contracts include the following two command-line software:

Solc:solidity Intelligent contract Compiler, official download

Web3j:web3j command line tool, official download

You can run solc directly after downloading, such as verifying the installation:

~ $solc

After downloading the web3j command line tool, decompress it with unzip, and then execute the web3j in it. For example:

~ $web3j

These two tools are mainly used for the processing of solidity smart contracts, which we have ignored for the time being.

5. Hello,web3j

Now we can create a directory, as well as App.java and build.gradle files, to implement the hello world application of web3j:

~ $mkdir hubwiz & & cd hubwiz~/hubwiz$ touch App.java build.gradle

Write the following App.java:

Package com.hubwiz.demo;import org.web3j.protocol.Web3j;import org.web3j.protocol.http.HttpService;import org.web3j.protocol.core.Request;import org.web3j.protocol.core.methods.request.*;import org.web3j.protocol.core.methods.response.*;public class App {public static void main (String [] args) throws Exception {Web3j web3j = Web3j.build (new HttpService ("http://localhost:8545")); Request)

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