nashorn-maven-plugin

Purpose

nashorn-maven-plugin allows execute little piece of Javascript code during build. It is lightweight alternative to implement regular plugin

Example

Let say you want touch file 'x' during build. Classic Ant way:

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-antrun-plugin</artifactId>
      <version>1.6</version>
      <executions>
        <execution>
          <phase>process-resources</phase>
            <configuration>
              <target>
                <touch file="${basedir}/x" />
              </target>
            </configuration>
            <goals><goal>run</goal></goals>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

Nashorn way:

<build>
  <plugins>
    <plugin>
      <groupId>io.github.michaldo</groupId>
      <artifactId>nashorn-maven-plugin</artifactId>
      <version>0.0.2</version>
      <executions>
        <execution>
          <phase>process-resources</phase>
          <goals><goal>eval</goal></goals>
          <configuration>
            <script>
              var path = java.nio.file.Paths.get($basedir, 'x');
              var Files = Java.type('java.nio.file.Files');
              if (!Files.exists(path)) {
                Files.createFile(path);
              } else {
                var FileTime = Java.type('java.nio.file.attribute.FileTime');
                Files.setLastModifiedTime(path, FileTime.from(java.time.Instant.now()))
              }
            </script>
          </configuration>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

No benefit of Nashorn way. But let say you have multi-module project with many jar and war module and you want to touch 'x' only for war module. For Ant it's impossible, huh? For Nashorn it is pretty easy

<build>
  <plugins>
    <plugin>
      <groupId>io.github.michaldo</groupId>
      <artifactId>nashorn-maven-plugin</artifactId>
      <version>0.0.2</version>
      <executions>
        <execution>
          <phase>process-resources</phase>
          <goals><goal>eval</goal></goals>
          <configuration>
            <script>
              
              if ($project.packaging != 'war') return;
              
              var path = java.nio.file.Paths.get($basedir, 'x');
              var Files = Java.type('java.nio.file.Files');
              if (!Files.exists(path)) {
                Files.createFile(path);
              } else {
                var FileTime = Java.type('java.nio.file.attribute.FileTime');
                Files.setLastModifiedTime(path, FileTime.from(java.time.Instant.now()))
              }
            </script>
          </configuration>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

Usage

<plugin>
  <groupId>io.github.michaldo</groupId>
  <artifactId>nashorn-maven-plugin</artifactId>
  <version>0.0.2</version>
  <executions>
    <execution>
      <phase>initialize</phase>
      <goals><goal>eval</goal></goals>
        <configuration>
        <script>
          print('hello world');
        </script>
      </configuration>
    </execution>
  </executions>
</plugin>

Goals

nashorn:eval: executes javascript code

Parameters

script : required script code

Maven API

The following Maven objects are injected in Javascript space

Variable	Class
$project	actual MavenProject
$session	MavenSession
$mojo	MojoExecution
$plugin	MojoExecution.getMojoDescriptor().getPluginDescriptor()
$settings	MavenSession.getSettings()
$localRepository	MavenSession.getLocalRepository()()
$reactorProjects	MavenSession.getProjects()
$repositorySystemSession	MavenSession.getRepositorySession()
$executedProject	MavenProject.getExecutionProject()
$basedir	MavenProject.getBasedir()

Requirements

Maven 3.1

Java 8