JRE Maven Plugin

This Maven plugin allows you to bundle a JRE inside your project.
It can download the JRE from Adoptium and optionally unzip it to a specified directory.

🚀 Usage

Add the following to your pom.xml to use the plugin:

<build>
    <plugins>
        <plugin>
            <groupId>io.github.samurai016.plugins</groupId>
            <artifactId>jre-maven-plugin</artifactId>
            <version>1.0.0</version>
            <executions>
                <execution>
                    <goals>
                        <goal>jre-bundler</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <!-- Optional: Configure the parameters as needed -->
                <version>21</version>
                <outputdir>${project.build.directory}/bundled-jre</outputdir>
                <unzipto>${project.build.directory}/final-jre</unzipto>
            </configuration>
        </plugin>
    </plugins>
</build>

🔧 Plugin Parameters

Parameter	Default Value	Description
version	${maven.compiler.source}	The version of the JRE to download. Specify a valid Java feature version (e.g., 8, 11, 17, 21).
jvmImpl	hotspot	The JVM implementation to download. Currently, only hotspot is supported. See Adoptium V3 API docs for more details
architecture	x64	The architecture of the JRE to download (e.g., x64, arm64). See Adoptium V3 API docs for more details
os	windows	The operating system for the JRE (e.g., windows, linux, mac). See Adoptium V3 API docs for more details
imagetype	jre	The type of image to download. It is recommended to use the jre image type as it is the smallest version available. See Adoptium V3 API docs for more details
vendor	eclipse	The vendor providing the JRE. Currently, only eclipse (Adoptium) is supported. See Adoptium V3 API docs for more details
outputdir	${project.build.directory}/jre	The directory where the JRE will be downloaded. You can use variables in the form {{variable}}.
outputfilename	<release_name>.zip	The name of the output file. If not specified, it will use the release name of the JRE with .zip appended if necessary.
unzipto	N/A	The directory where the JRE will be unzipped. If not specified, the JRE will not be unzipped.
movetoroot	true	If true, the contents of the first-level folder in the JRE zip will be moved to the root directory. If false, they will stay nested.

🛠️ Example Configuration

Basic Example

<configuration>
    <version>21</version>
    <!-- <version>${maven.compiler.source}</version> Uncomment this to use the same version as the project -->
    <outputdir>${project.build.directory}/bundled-jre</outputdir>
    <unzipto>${project.build.directory}/unpacked-jre</unzipto>
    <movetoroot>true</movetoroot>
</configuration>

Advanced Example

In this example, we specify all possible configuration options:

<configuration>
    <version>21</version>
    <jvmImpl>hotspot</jvmImpl>
    <architecture>x64</architecture>
    <os>linux</os>
    <imagetype>jre</imagetype>
    <vendor>eclipse</vendor>
    <outputdir>${project.build.directory}/bundled-jre</outputdir>
    <outputfilename>jre.zip</outputfilename>
    <unzipto>${project.build.directory}/jre</unzipto>
    <movetoroot>true</movetoroot>
</configuration>

Real World Example

In this example, we use the same JRE version as the project and we use:

• jre-maven-plugin to bundle the JRE.
• maven-shade-plugin to create a fat JAR (with dependencies).
• launch4j-maven-plugin to create an executable file for Windows which includes the JRE.

In this way, we can create a standalone executable file that runs on Windows without requiring the user to have Java installed or to update any existing Java installations.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>io.github.samurai016.plugins.example</groupId>
    <artifactId>jre-maven-plugin-example</artifactId>
    <version>0.1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <maven.compiler.source>21</maven.compiler.source>
        <maven.compiler.target>21</maven.compiler.target>
        <maven.compiler.release>21</maven.compiler.release>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <app.mainClass>io.github.samurai016.plugins.example.App</app.mainClass>
    </properties>

    <build>
        <plugins>
            <!-- Maven JRE Plugin: Bundle JRE -->
            <plugin>
                <groupId>io.github.samurai016.plugins</groupId>
                <artifactId>jre-maven-plugin</artifactId>
                <version>1.0.0</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>jre-bundler</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <version>${maven.compiler.release}</version>
                    <architecture>x64</architecture>
                    <imagetype>jre</imagetype>
                    <os>windows</os>
                    <unzipto>target/jre</unzipto>
                </configuration>
            </plugin>

            <!-- Maven Shade Plugin: Create a single executable jar -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <transformers>
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>${app.mainClass}</mainClass>
                                </transformer>
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
                            </transformers>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

            <!-- Launch4j Maven Plugin: Create a Windows executable -->
            <plugin>
                <groupId>com.akathist.maven.plugins.launch4j</groupId>
                <artifactId>launch4j-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <id>l4j-clui</id>
                        <phase>package</phase>
                        <goals>
                            <goal>launch4j</goal>
                        </goals>
                        <configuration>
                            <headerType>console</headerType>
                            <outfile>target/${project.artifactId}.exe</outfile>
                            <jar>target/${project.artifactId}.jar</jar>
                            <!-- Other launch4j configuration options -->
                            <jre>
                                <path>./jre/${jre.version};%JAVA_HOME%;%PATH%</path>
                            </jre>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

🔍 How It Works

1. Parameter Configuration: The plugin reads the configuration parameters specified in pom.xml.
2. Adoptium API Interaction: It retrieves the latest available JRE version from Adoptium.
3. Download: The JRE binary is downloaded to the specified output directory.
4. Unzip (Optional): If the unzipto parameter is set, the JRE is extracted to the given directory.
5. Move to Root (Optional): If movetoroot is true, the contents of the first-level folder in the archive are moved to the root.

📌️ Example Directory Structure

With the following configuration:

<outputdir>${project.build.directory}/bundled-jre</outputdir>
<outputfilename>jre.zip</outputfilename>
<unzipto>${project.build.directory}/jre</unzipto>
<movetoroot>true</movetoroot>

The result will be:

/target/bundled-jre
├── jre.zip
/target/jre
├── bin/
├── lib/
├── ...

💻 Development

To build and test the plugin locally, run:

mvn clean install

🛡️ License

This project is licensed under the GNU General Public License v3.0.

🤝 Contributing

Contributions are welcome! Please fork the repository and submit a pull request.

🐛 Issues

If you encounter any problems, feel free to open an issue.

❤️ Credits

Thanks to Adoptium for providing reliable JRE builds.