Migrate build system from Maven to Gradle

The main motivation for migrating to Gradle is the build duration. With
the introduction of the new multi-module project structure build times
of the Maven-based build increased heavily. Tests showed that Gradle can
build the project much faster.

In addition to reducing build times, Gradle allows to better minimize
code duplication in build scripts: Maven's solution for centralising
build configuration in a multi-module project are parent modules. The
disadvantage of this solution is that the parent modules need to be
published along with the actual artifacts.  These additional
publications, which are technically only required for building the
artifacts, are a source of confusion for users.

Other than Maven Gradle clearly separates the organisation of the build
scripts from the published dependency information. This enables us to
coveniently organise the build scripts while at the same time only
publish the actual artifacts.

Gradle's philosophy for configuring a build also opens new options for
organising the release process.

Author: cboehme

.gitignore

@@ -1,6 +1,11 @@
 # Ignore temporary maven files:
 target/
 
+# Ignore temporary gradle files:
+.gradle
+.gradletasknamecache
+build
+
 # Ignore Eclipse project files:
 .checkstyle
 .pmd
@@ -15,6 +20,11 @@ target/
 *.iml
 .idea
 /out/
+/*/out/
 
 # Ignore IntelliJ JIRA plugin
 atlassian-ide-plugin.xml
+
+# Ignore files generated by CI:
+buildbot.keyring
+

.travis.yml

@@ -1,12 +1,9 @@
-language: java
 sudo: false
+dist: trusty
+language: java
 jdk:
   - oraclejdk8
 
-env:
-  global:
-    - secure: "V5OtkOZRRjjep5ig8A/z9hVOCPYJZRyuPjQ1bmGgtjtzPuLS4x5FSBHLZ+OERdR8VS3nJh05UoNVvxS6tdQ3pbIoJUojbNEFCABGVI+krvsbbar7nDZiF9yKI4mxP60sPvlD7gQ0n0Bdq1BpZGqHmwESsocAMd24oZi+8Nj80sk="
-    - secure: "T9FcW2f0orue6i+Pvc1hE64mSoyOSwJFL9OrCBmhom5QW51Q8gP71DpEIz8fc6MvvU3wpSbTg5+lvbnTRdQCxmQzBeZb4yfdwUElldxaBqQaqVJWYBfoz0T1iznNA9WV3kHoHiDcb0iy3w/yzDxieQWjwj/69lKCvn8o425se7E="
-
 after_success:
-  - "[[ $TRAVIS_BRANCH == \"master\" ]] && { python travis-ci/configure-mvn.py ; mvn clean deploy --settings ~/.m2/mySettings.xml -Dgpg.skip=true -P deploy ; }"
+  - ./travis/publish.sh
+

README.md

@@ -61,17 +61,21 @@ TODO: Add
 
 # Building metafacture-core from source
 
-Building metafacture-core from source is easy. All you need is git and [maven](http://maven.apache.org/):
+Building metafacture-core from source is easy. All you need is git and JDK 8:
 
-1. Clone the metafacture-core repository:
+1. Clone the metafacture-core repository and change into the directory:
 
-        $ git clone https://github.com/culturegraph/metafacture-core.git
+    ```bash
+    $ git clone https://github.com/culturegraph/metafacture-core.git
+    $ cd metafacture-core
+    ```
 
-2. Build and install in your local repository:
+2. Invoke the gradle-wrapper to download Gradle and build metafacture-core:
 
-        $ mvn clean install
-
-    It is important to perform this step *before* importing the project into your IDE because it generates the lexer and parser sources for Flux from antlr grammar definitions. Otherwise your IDE will fail to compile the sources if it has integrated background compilation (like Eclipse has, for instance).
+   ```bash
+   $ ./gradlew install
+   ```
+   on Windows call `gradlew.bat install` instead.
 
 See [Code Quality and Style](https://github.com/culturegraph/metafacture-core/wiki/Code-Quality-and-Style) on the wiki for further information on the sources.
 

build.gradle

@@ -0,0 +1,222 @@
+/*
+ * Copyright 2017 Christoph Böhme
+ *
+ * Licensed under the Apache License, Version 2.0 the "License";
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import java.util.regex.Matcher
+
+plugins {
+  id 'org.ajoberstar.grgit' version '2.0.0-rc.1'
+}
+
+ext.gitTag = getGitTag()
+
+allprojects {
+  group = 'org.culturegraph'
+  version = getVersionFrom(rootProject.ext.gitTag) ?: '5.0.0-SNAPSHOT'
+  ext.mavenName = null
+}
+
+configure(subprojects.findAll { it.name != 'metafacture-runner' }) {
+  apply plugin: 'java-library'
+}
+
+project(':metafacture-runner') {
+  apply plugin: 'java'
+}
+
+subprojects {
+  apply plugin: 'signing'
+  apply plugin: 'maven'
+
+  sourceCompatibility = 1.8
+  targetCompatibility = 1.8
+
+  tasks.withType(JavaCompile) {
+    options.encoding = 'UTF-8'
+  }
+
+  task sourceJar(type: Jar) {
+    dependsOn tasks.classes
+    from sourceSets.main.allJava
+    classifier 'sources'
+    description 'Creates a jar containing the source files of this project.'
+    group 'build'
+  }
+
+  task javadocJar(type: Jar) {
+    dependsOn tasks.javadoc
+    from tasks.javadoc
+    classifier 'javadoc'
+    description 'Creates a jar containing the javadoc of this project.'
+    group 'build'
+  }
+
+  task publish {
+    dependsOn tasks.uploadArchives
+  }
+
+  configurations {
+    mavenDeploySupport
+  }
+
+  dependencies {
+    mavenDeploySupport "org.apache.maven.wagon:wagon-http:2.2"
+  }
+
+  artifacts {
+    archives sourceJar
+    archives javadocJar
+  }
+
+  signing {
+    required {
+      rootProject.ext.gitTag != null &&
+          gradle.taskGraph.hasTask(tasks.uploadArchives)
+    }
+    sign configurations.archives
+  }
+
+  def mavenProjectDescription = {
+    name project.ext.mavenName ?: project.name
+    if (project.description) {
+      description project.description
+    }
+    url 'https://github.com/culturegraph/metafacture-core'
+    inceptionYear '2011'
+    organization {
+      name 'Deutsche Nationalbibliothek'
+      url 'http://dnb.de/'
+    }
+    licenses {
+      license {
+        name 'The Apache License, Version 2.0'
+        url 'http://www.apache.org/licenses/LICENSE-2.0.txt'
+      }
+    }
+    mailingLists {
+      mailingList {
+        name 'Metafacture Mailing List'
+        post '[email protected]'
+        subscribe '[email protected]'
+        unsubscribe '[email protected]'
+        archive 'http://lists.dnb.de/pipermail/metafacture/'
+      }
+    }
+    scm {
+      connection 'scm:git:https://github.com/culturegraph/metafacture-core.git'
+      developerConnection 'scm:git:https://github.com/culturegraph/metafacture-core.git'
+      url 'https://github.com/culturegraph/metafacture-core'
+      tag rootProject.ext.gitTag ?: 'HEAD'
+    }
+    issueManagement {
+      system 'Github'
+      url 'https://github.com/culturegraph/metafacture-core/issues'
+    }
+    ciManagement {
+      system 'Travis CI'
+      url 'https://travis-ci.org/culturegraph/metafacture-core'
+    }
+  }
+
+  install {
+    repositories {
+      mavenInstaller {
+        pom.project mavenProjectDescription
+        beforeDeployment {
+          MavenDeployment deployment -> signing.signPom(deployment)
+        }
+      }
+    }
+  }
+
+  uploadArchives {
+    repositories {
+      mavenDeployer {
+        configuration = configurations.mavenDeploySupport
+        if (project.hasProperty('releaseRepositoryUrl')) {
+          repository(url: releaseRepositoryUrl) {
+            if (project.hasProperty('releaseRepositoryUser')) {
+              authentication(userName: releaseRepositoryUser,
+                             password: releaseRepositoryPassword)
+            }
+          }
+        }
+        if (project.hasProperty('snapshotRepositoryUrl')) {
+          snapshotRepository(url: snapshotRepositoryUrl) {
+            if (project.hasProperty('snapshotRepositoryUser')) {
+              authentication(userName: snapshotRepositoryUser,
+                             password: snapshotRepositoryPassword)
+            }
+          }
+        }
+        pom.project mavenProjectDescription
+        beforeDeployment {
+          MavenDeployment deployment -> signing.signPom(deployment)
+        }
+      }
+    }
+  }
+
+  repositories {
+    mavenLocal()
+    mavenCentral()
+  }
+}
+
+def getGitTag() {
+  def tags = getGitTags(grgit)
+  if (tags.isEmpty()) {
+    logger.lifecycle("HEAD is not tagged. Making a snapshot build")
+    return null
+  }
+  if (tags.size() > 1) {
+    logger.warn("HEAD has ${tags.size()} tags. Making a snapshot build")
+    return null
+  }
+  def tagName = tags[0].name
+  logger.lifecycle("Found tag $tagName. Making a release build")
+  return tagName
+}
+
+def static getGitTags(grgit) {
+  def tags = []
+  for (tag in grgit.tag.list()) {
+    if (tag.commit == grgit.head()) {
+      tags.add tag
+    }
+  }
+  return tags
+}
+
+def static extractVersion(tag) {
+  Matcher matcher =
+      tag =~ /metafacture-core-(\d+\.\d+\.\d+(-[-A-Za-z0-9]+)?)/
+  if (!matcher.matches()) {
+    throw new GradleException("""\
+        Unsupported tag format: $tag
+        Could not extract version from tag. Supported tag formats are
+            metafacture-core-X.Y.Z and
+            metafacture-core-X.Y.Z-QUALIFIER
+        """.stripIndent())
+  }
+  return matcher.group(1)
+}
+
+def static getVersionFrom(tag) {
+  if (tag != null) {
+    return extractVersion(tag)
+  }
+  return null
+}

gradle/wrapper/gradle-wrapper.jar

@@ -0,0 +1,6 @@
+#Sun Jul 30 20:26:57 CEST 2017
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.0.2-all.zip