Gradle plugin for Embulk plugins

Versions

Gradle Plugin version	Expected Gradle version
v0.7.0	Gradle 8.7
v0.6.2	Gradle 7.6 (7.6.3)
v0.6.1	Gradle 7.6 (7.6.1)
v0.6.0	Gradle 7.6 (7.6.1)

Quick Start

plugins {
    id "java"
    id "maven-publish"
    id "signing"

    // Apply this Gradle plugin.
    id "org.embulk.embulk-plugins" version "0.7.0"
}

repositories {
    mavenCentral()
}

// Set your own group ID. It would typically be:
// - From your own domain (ex. "com.example"), or
// - From your GitHub account (ex. "io.github.your-github-user").
//
// Note that you should not use "org.embulk" unless the plugin is maintained under: https://github.com/embulk
group = "..."

// Set the version of the plugin.
version = "0.1.5-SNAPSHOT"

// Set the description of your plugin.
description = "An Embulk plugin to load example data."

configurations {
    // We'd recommend to enable dependency locking so that you are aware of transitive dependencies.
    // See: https://docs.gradle.org/current/userguide/dependency_locking.html
    compileClasspath.resolutionStrategy.activateDependencyLocking()
    runtimeClasspath.resolutionStrategy.activateDependencyLocking()
}

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(8)
    }

    // "javadoc" JAR and "sources" JAR are required to publish the plugin to Maven Central.
    withJavadocJar()
    withSourcesJar()
}

dependencies {
    // The versioning rule of "embulk-spi" has been independent from Embulk versions since v0.11.
    // It would be two digits, such as "0.11", "1.0", "1.1", ...
    // This is the version of Embulk SPI, as a contract between the core and plugins.
    compileOnly "org.embulk:embulk-spi:0.11"

    // An Embulk plugin should not depend on "embulk-core" if the plugin is ready for Embulk v0.11 and v1.0.

    // An Embulk plugin would usually depend some "embulk-util-*" librarires, for example, "embulk-util-config".
    // Note that Gradle 7+ needs to declare dependencies by "implementation", not by "compile".
    implementation "org.embulk:embulk-util-config:0.5.0"

    // ...

    testImplementation "junit:junit:4.13.2"

    // The Embulk main packages are often required for testing.
    testImplementation "org.embulk:embulk-spi:0.11"
    testImplementation "org.embulk:embulk-core:0.11.0"
    testImplementation "org.embulk:embulk-deps:0.11.0"
    testImplementation "org.embulk:embulk-junit4:0.11.0"
}

embulkPlugin {
    // Set the plugin's main class.
    mainClass = "org.embulk.input.example.ExampleInputPlugin"

    // Set: "decoder", "encoder", "filter", "formatter", "guess", "input", "output", or "parser"
    category = "input"

    // Set the "type" of the Embulk plugin used in Embulk's configuration YAML.
    // For instance, it would be "example" for "embulk-input-example".
    type = "example"
}

// It would be a good habit to contain the LICENSE file(s) at "META-INF/" in your plugin packages.
jar {
    metaInf {
        from rootProject.file("LICENSE")
    }
}
sourcesJar {
    metaInf {
        from rootProject.file("LICENSE")
    }
}
javadocJar {
    metaInf {
        from rootProject.file("LICENSE")
    }
}

// The publishing settings are usually required to publish the plugin to Maven Central.
// Publish it by: "./gradlew publishMavenPublicationToMavenRepository"
publishing {
    publications {
        maven(MavenPublication) {
            groupId = project.group
            artifactId = project.name

            from components.java
            // javadocJar and sourcesJar are added by java.withJavadocJar() and java.withSourcesJar() above.
            // See: https://docs.gradle.org/current/javadoc/org/gradle/api/plugins/JavaPluginExtension.html

            // Some pom.xml attributes are mandatory in Maven Central.
            // See: https://central.sonatype.org/pages/requirements.html
            pom {
                packaging "jar"

                name = project.name
                description = project.description
                url = "https://.../"

                licenses {
                    license {
                        // See: http://central.sonatype.org/pages/requirements.html#license-information
                        name = "..."
                        url = "..."
                        distribution = "repo"
                    }
                }

                developers {
                    developer {
                        name = "..."
                        email = "..."
                    }
                    developer {
                        name = "..."
                        email = "..."
                    }
                    // ...
                }

                scm {
                    connection = "scm:git:git://github.com/.../....git"
                    developerConnection = "scm:git:git@github.com:.../....git"
                    url = "https://github.com/.../..."
                }
            }
        }
    }

    repositories {
        maven {  // publishMavenPublicationToMavenCentralRepository
            name = "mavenCentral"

            // Note that the URLs may be different in your case, depending on your OSSRH / Sonatype registration.
            // See: https://central.sonatype.org/publish/publish-maven/
            if (project.version.endsWith("-SNAPSHOT")) {
                url "https://oss.sonatype.org/content/repositories/snapshots"
            } else {
                url "https://oss.sonatype.org/service/local/staging/deploy/maven2"
            }

            // Just an optional technique to specify OSSRH username and password from Gradle properties.
            //
            // It is sometimes useful to publish the plugin to Maven Central from CI like GitHub Actions.
            credentials {
                username = project.hasProperty("ossrhUsername") ? ossrhUsername : ""
                password = project.hasProperty("ossrhPassword") ? ossrhPassword : ""
            }
        }
    }
}

// The signing settings are usually required to publish the plugin to Maven Central.
// See: https://central.sonatype.org/publish/requirements/gpg/
signing {
    // Just an optional technique to specify a GPG key and password from Gradle properties.
    //
    // Set your GPG key into "signingKey" in the ASCII armor format.
    // Set your GPG key password into "signingPassword".
    //
    // It is sometimes useful to publish the plugin to Maven Central from CI like GitHub Actions.
    if (project.hasProperty("signingKey") && project.hasProperty("signingPassword")) {
        logger.lifecycle("Signing with an in-memory key.")
        useInMemoryPgpKeys(signingKey, signingPassword)
    }

    sign publishing.publications.maven
}

// Enable the following "gem" and "gemPush" tasks if you want to publish your plugin also as a Ruby Gem.

// gem {
//     authors = [ "..." ]
//     email = [ "..." ]
//     // "description" of the Ruby Gem would come from "description" of the Gradle project.
//     summary = "Example input plugin for Embulk"
//     homepage = "https://.../"
//     licenses = [ "..." ]  // See: https://guides.rubygems.org/specification-reference/#license=
//
//     from("LICENSE")  // If you want to include LICENSE file(s) in the Ruby Gem package.
// }

// Push it by: "./gradlew gemPush"
// gemPush {
//     host = "https://rubygems.org"
// }

How to migrate from old build.gradle

1. Upgrade your Gradle wrapper to 7.6.3.
2. Define group, version, and description in your Gradle project.
   • group should NOT be "org.embulk" unless your project is under: https://github.com/embulk.

     group = "com.example"
     version = "0.1.5-SNAPSHOT"
     description = "An Embulk plugin to load example data."
     

3. Replace dependencies on Embulk.
   • Old (without this Gradle plugin):

     compile "org.embulk:embulk-core:0.9.23"
     provided "org.embulk:embulk-core:0.9.23"
     

   • New:

     compileOnly "org.embulk:embulk-spi:0.11"
     
     testImplementation "org.embulk:embulk-spi:0.11"
     testImplementation "org.embulk:embulk-core:0.11.0"
     testImplementation "org.embulk:embulk-deps:0.11.0"
     testImplementation "org.embulk:embulk-junit4:0.11.0"
     

4. Remove an unnecessary configuration.
   • provided

   configurations {
       provided
   }
   

5. Remove unnecessary tasks.
   • classpath

   task classpath(type: Copy, dependsOn: ["jar"]) {
       doFirst { file("classpath").deleteDir() }
       from (configurations.runtime - configurations.provided + files(jar.archivePath))
       into "classpath"
   }
   clean { delete "classpath" }
   

   • gem

   task gem(type: JRubyExec, dependsOn: ["gemspec", "classpath"]) {
       jrubyArgs "-rrubygems/gem_runner", "-eGem::GemRunner.new.run(ARGV)", "build"
       script "${project.name}.gemspec"
       doLast { ant.move(file: "${project.name}-${project.version}.gem", todir: "pkg") }
   }
   

   • gemPush

   task gemPush(type: JRubyExec, dependsOn: ["gem"]) {
       jrubyArgs "-rrubygems/gem_runner", "-eGem::GemRunner.new.run(ARGV)", "push"
       script "pkg/${project.name}-${project.version}.gem"
   }
   

   • package

   task "package"(dependsOn: ["gemspec", "classpath"]) {
       doLast {
           println "> Build succeeded."
           println "> You can run embulk with '-L ${file(".").absolutePath}' argument."
       }
   }
   

   • gemspec

   task gemspec {
       ext.gemspecFile = file("${project.name}.gemspec")
       inputs.file "build.gradle"
       outputs.file gemspecFile
       doLast { gemspecFile.write($/
   Gem::Specification.new do |spec|
     spec.name          = "${project.name}"
     spec.version       = "${project.version}"
     spec.authors       = ["Somebody Somewhere"]
     spec.summary       = %[Example input plugin for Embulk]
     spec.description   = %[An Embulk plugin to load example data.]
     spec.email         = ["somebody@example.com"]
     spec.licenses      = ["MIT"]
     spec.homepage      = "https://example.com"
   
     spec.files         = `git ls-files`.split("\n") + Dir["classpath/*.jar"]
     spec.test_files    = spec.files.grep(%r"^(test|spec)/")
     spec.require_paths = ["lib"]
   
     #spec.add_dependency 'YOUR_GEM_DEPENDENCY', ['~> YOUR_GEM_DEPENDENCY_VERSION']
     spec.add_development_dependency 'bundler'
     spec.add_development_dependency 'rake', ['>= 10.0']
   end
   /$)
       }
   }
   clean { delete "${project.name}.gemspec" }
   

6. Remove an unnecessary file.
   • lib/embulk/<category>/<type>.rb

     Embulk::JavaPlugin.register_input(
       "example", "org.embulk.input.example.ExampleInputPlugin",
       File.expand_path('../../../../classpath', __FILE__))
     

7. Apply this Gradle plugin "org.embulk.embulk-plugins".
   • In Gradle's plugins DSL:

     plugins {
         id "java"
         id "maven-publish"
         id "signing"
         id "org.embulk.embulk-plugins" version "0.7.0"
     }
     

8. Remove unnecessary JRuby/Gradle plugin.
   • Plugin application:

         id "com.github.jruby-gradle.base" version "0.1.5"
     

   • Class import:

     import com.github.jrubygradle.JRubyExec
     

9. Configure the task embulkPlugin.
   • mainClass, category, and type are mandatory. For example:

     embulkPlugin {
         mainClass = "org.embulk.input.dummy.DummyInputPlugin"
         category = "input"
         type = "dummy"
     }
     

10. Configure publishing. Recommended to publish your Embulk plugin to Maven Central.
    • See the example above.
11. Configure signing. It is mandatory to publish your Embulk plugin to Maven Central.
    • See the example above.
12. Configure gem and gemPush if you want to publish your Embulk plugin also as a Ruby Gem.
    • See the example above.
    • Note that JRuby's rubygems may not support multi-factor authentication (OTP) for https://rubygems.org/ yet. You may need to set your authentication level to "UI only".
      • https://guides.rubygems.org/setting-up-multifactor-authentication/

What this Gradle plugin does?

This Gradle plugin has two main purposes to satisfy two requirements as an Embulk plugin.

One of the requirements is to get Embulk plugin's pom.xml to include all dependencies as the direct first-level dependencies without any transitive dependency. This is an important restriction to keep dependencies consistent between plugin development and Embulk's runtime. (Indeed, Embulk's PluginClassLoader is implemented for Maven-based plugins to load only the direct first-level dependencies without any transitive dependency.)

The other requirement is to add some required attributes in MANIFEST.MF.

In addition, this Gradle plugin provides some support for publishing RubyGems-based plugins.

This Gradle plugin depends on Gradle's java-plugin and maven-publish-plugin.

For Maintainers of this Gradle plugin

Release

Modify version in build.gradle at a detached commit, and then tag the commit with an annotation.

git checkout --detach master

(Edit: Remove "-SNAPSHOT" in "version" in build.gradle.)

git add build.gradle

git commit -m "Release vX.Y.Z"

git tag -a vX.Y.Z

(Edit: Write a tag annotation in the changelog format.)

See Keep a Changelog for the changelog format. We adopt a part of it for Git's tag annotation like below.

## [X.Y.Z] - YYYY-MM-DD

### Added
- Added a feature.

### Changed
- Changed something.

### Fixed
- Fixed a bug.

Push the annotated tag, then. It triggers a release operation on GitHub Actions after approval.

git push -u origin vX.Y.Z