web3j Gradle Plugin

Gradle plugin that generates web3j Java wrappers from Solidity smart contracts. It smoothly integrates with your project's build lifecycle by adding specific tasks that can be also run independently.

Plugin configuration

Before you start, you will need to install the Solidity compiler if is not already installed in your computer.

In addition, the minimum Gradle version to run the plugin is 4.9 and the recommended 5.2.x.

Using the buildscript convention

To install the web3j Plugin using the old Gradle buildscript convention, you should add the following to the first line of your build file (at the moment only release versions are supported in Gradle, not SNAPSHOT):

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'org.web3j:web3j-gradle-plugin:4.1.3'
    }
}

apply plugin: 'org.web3j'

Using the plugins DSL

Alternatively, if you are using the more modern plugins DSL, add the following line to your build file:

plugins {
    id 'org.web3j' version '4.1.3'
}

Then run your project containing Solidity contracts:

./gradlew build

After applying the plugin, the base directory for generated code (by default $buildDir/generated/source/web3j) will contain a directory for each source set (by default main and test) containing the smart contract wrappers Java classes.

Project dependencies

The plugin requires the core web3j dependency to be declared in your project. The minimum version is 4.0 but is recommended to use the latest available release.

dependencies {
    implementation "org.web3j:core:$web3jVersion"
}

Code generation

The web3j DSL allows to configure the generated code, e.g.:

web3j {
    generatedPackageName = 'com.mycompany.{0}'
    generatedFilesBaseDir = "$buildDir/custom/destination"
    excludedContracts = ['Ownable']
    useNativeJavaTypes = false
}

The properties accepted by the DSL are listed in the following table:

Name	Type	Default value	Description
generatedPackageName	String	${group}.web3j or org.web3j.{0}	Generated contract wrappers package.
generatedFilesBaseDir	String	$buildDir/generated/source/web3j	Generated Java code output directory.
excludedContracts	String[]	[]	Excluded contract names from wrapper generation.
includedContracts	String[]	[]	Included contract names from wrapper generation. Has preference over excludedContracts.
useNativeJavaTypes	Boolean	true	Generate smart contract wrappers using native Java types.

The generatedPackageName is evaluated as a message format string accepting a single parameter between curly brackets ({0}), allowing to format the generated value using the contract name. For convenience, when applied to a Java package name it will be converted to lower case.

For instance, a generatedPackageName set to ${group}.{0} in a project with group com.mycompany, a Solidity contract named MyToken.sol will be generated in the package com.mycompany.mytoken.

Also, the default value contains the ${group} property, which corresponds to your project artifact group (e.g. com.mycompany). If the project does not define a group property, the generated package name will be org.web3j.{0}.

Note that message format parameters are not Gradle properties and should not be preceded by $.

Source sets

By default, all .sol files in $projectDir/src/main/solidity will be processed by the plugin. To specify and add different source sets, use the sourceSets DSL:

sourceSets {
    main {
        solidity {
            srcDir { 
                "my/custom/path/to/solidity" 
             }
        }
    }
}

Check the Solidity Plugin documentation to configure the smart contracts source code directories.

Output directories for generated smart contract wrappers Java code will be added to your build automatically.

Plugin tasks

The Java Plugin adds tasks to your project build using a naming convention on a per source set basis (i.e. compileJava, compileTestJava).

Similarly, the Solidity plugin will add the generateContractWrappers task for the project main source set, and a generate[SourceSet]ContractWrappers for each remaining source set (e.g. test).

To obtain a list and description of all added tasks, run the command:

./gradlew tasks --all