web3j-maven-plugin

web3j maven plugin is used to create java classes based on the solidity contract files.

Usage

The base configuration for the plugin will take the solidity files from src/main/resources and generates the java classes into the folder src/main/java.

<build>
    <plugins>
        <plugin>
            <groupId>org.web3j</groupId>
            <artifactId>web3j-maven-plugin</artifactId>
            <version>4.12.1</version>
            <configuration>
                <soliditySourceFiles/>
            </configuration>
        </plugin>
    </plugins>
</build>

to run the plugin execute the goal generate-sources

mvn web3j:generate-sources

Configuration

The are several variable to select the solidity source files, define a source destination path or change the package name.

Name	Format	Default value
<packageName/>	valid java package name	org.web3j.model
<outputDirectory><java/></outputDirectory>	relative or absolute path of the generated for 'Java files	value in <sourceDestination/>
<outputDirectory><bin/></outputDirectory>	relative or absolute path of the generated for 'Bin' files	value in <sourceDestination/>
<outputDirectory><abi/></outputDirectory>	relative or absolute path of the generated for 'ABI' files	value in <sourceDestination/>
<sourceDestination/>	relative or absolute path of the generated files (java, bin, abi)	src/main/java
<outputFormat/>	generate Java Classes(java), ABI(abi) and/or BIN (bin) Files (comma separated)	java
<nativeJavaType/>	Creates Java Native Types (instead of Solidity Types)	true
<outputJavaParentContractClassName/>	Sets custom(? extends org.web3j.tx.Contract) class as a parent for java generated code	org.web3j.tx.Contract
<soliditySourceFiles>	Standard maven fileset	<soliditySourceFiles> <directory>src/main/resources</directory> <includes> <include>**/*.sol</include> </includes> </soliditySourceFiles>
<abiSourceFiles>	Standard maven fileset	<abiSourceFiles> <directory>src/main/resources</directory> <includes> <include>**/*.json</include> </includes> </abiSourceFiles>
<contract>	Filter (<include> or <exclude>) contracts based on the name.	<contract> <includes> <include>greeter</include> </includes> <excludes> <exclude>mortal</exclude> <excludes> </contracts>
<pathPrefixes>	A list (<pathPrefixe>) of replacements of dependency replacements inside Solidity contract.

Configuration of outputDirectory has priority over sourceDestination

Getting Started

Create a standard java maven project. Add following <plugin> - configuration into the pom.xml file:

<plugin>
    <groupId>org.web3j</groupId>
    <artifactId>web3j-maven-plugin</artifactId>
    <version>4.11.1</version>
    <configuration>
        <packageName>com.zuehlke.blockchain.model</packageName>
        <sourceDestination>src/main/java/generated</sourceDestination>
        <nativeJavaType>true</nativeJavaType>
        <outputFormat>java,bin</outputFormat>
        <soliditySourceFiles>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.sol</include>
            </includes>
        </soliditySourceFiles>
        <abiSourceFiles>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.json</include>
            </includes>
        </abiSourceFiles>
        <outputDirectory>
            <java>src/java/generated</java>
            <bin>src/bin/generated</bin>
            <abi>src/abi/generated</abi>
        </outputDirectory>
        <contract>
            <includes>
                <include>greeter</include>
            </includes>
            <excludes>
                <exclude>mortal</exclude>
            </excludes>
        </contract>
        <pathPrefixes>
            <pathPrefix>dep=../dependencies</pathPrefix>
        </pathPrefixes>
    </configuration>
</plugin>

Add your solidity contract files into the folder src/main/resources. Make sure that the solidity files ends with .sol.

Start the generating process:

> mvn web3j:generate-sources

[INFO] --- web3j-maven-plugin:0.1.2:generate-sources (default-cli) @ hotel-showcase ---
[INFO] process 'HotelShowCaseProxy.sol'
[INFO] 	Built Class for contract 'HotelShowCaseProxy'
[INFO] 	Built Class for contract 'HotelShowCaseV2'
[INFO] 	Built Class for contract 'Owned'
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4.681 s
[INFO] Finished at: 2017-06-13T07:07:04+02:00
[INFO] Final Memory: 14M/187M
[INFO] ------------------------------------------------------------------------

Process finished with exit code 0

You find the generated java classes inside the directory src/main/java/generated/.

Next step is to interact with the smart contract. See for that deploying and interacting with smart contracts in the official web3j documentation.

For a multi module project configuration see following post from @fcorneli. In short: For pick up the generated java source files, you need the build-helper-maven-plugin configuration. Also, ${basedir} prefix is required within a multi-module project.