Merge branch 'maven-build-job' into 'latest'

## Objective

Build your Java project using [Apache Maven](http://maven.apache.org/) and JDK 11.

## How to use it

1. Make sure your Java project is set up to use Maven. You can refer to the [Maven quick start guide](http://maven.apache.org/guides/getting-started/index.html)

2. _(Recommended)_ Use the provided `pom.xml` in the example section below to get started. You are then free to customize your `pom.xml`

as you wish. For instance you can choose to use the [Spring Boot](https://spring.io/projects/spring-boot) framework that will

package your jar a different way and the job will still work and expose your shiny jars.

3. Add the job URL inside the `include` list of your `.gitlab-ci.yml` file  (see the [quick setup](/use-the-hub/#quick-setup)). You can specify [a fixed version](#changelog) instead of `latest`.

    ```yaml

      - remote: 'https://jobs.r2devops.io/latest/maven_build.yml'`

    ```

4. If you need to customize the job (stage, variables, ...) check the [jobs-customization](/use-the-hub/#jobs-customization)

5. Grab a ☕ while the job is running !

## Example pom.xml

```xml

<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>com.myorg.myproject</groupId>

<artifactId>myartifact</artifactId>

<packaging>jar</packaging>

<version>1.0-SNAPSHOT</version>

<build>

  <directory>${artifactsDirectory}</directory> <!-- This is mandatory for the job to work -->

  <pluginManagement>

    <plugins>

      <plugin>

        <groupId>org.apache.maven.plugins</groupId>

        <artifactId>maven-compiler-plugin</artifactId>

        <version>3.8.1</version>

      </plugin>

    </plugins>

  </pluginManagement>

  <plugins>

    <plugin>

      <groupId>org.apache.maven.plugins</groupId>

      <artifactId>maven-compiler-plugin</artifactId>

      <configuration>

        <source>11</source>

        <target>11</target>

      </configuration>

    </plugin>

  </plugins>

</build>

</project>

```

## Job details

* Job name: `maven_build`

* Docker image: [maven:3.6.3-jdk-11](https://hub.docker.com/_/maven)

* Default stage: `build`

* When: `always`

## Variables

| Name | Description | Default |

| ---- | ------------| ------- |

| `ARTIFACTS_DIR` | Customize the path where the artifacts will be created | `${CI_PROJECT_DIR}/artifacts` |

name: maven_build

description: Build a Java project with maven and expose built artifacts (jar, classes, etc.)

default_stage: build

icon: ⚙️

maintainer: alexlevy

license: MIT

labels:

  - Java

  - Build

images:

  'maven': '3.6.3-jdk-11'

tools:

  maven: '3.6.3'

stages:

  - build

maven_build:

  image:

    name: maven:3.6.3-jdk-11

    entrypoint: [""]

  stage: build

  variables:

    ARTIFACTS_DIR: ${CI_PROJECT_DIR}/artifacts

  script:

      - mkdir -p ${ARTIFACTS_DIR}

      - mvn -B clean install -DartifactsDirectory=${ARTIFACTS_DIR} -DskipTests

  artifacts: 

    when: always

    expose_as: "build"

    paths:

      - "${ARTIFACTS_DIR}"

* Initial version