3.2. Preparing to use Maven

Overview

This section gives a brief overview of how to prepare Maven for building Red Hat JBoss Fuse projects and introduces the concept of Maven coordinates, which are used to locate Maven artifacts.

Prerequisites

In order to build a project using Maven, you must have the following prerequisites:
  • Maven installation—Maven is a free, open source build tool from Apache. You can download the latest version from the Maven download page.
  • Network connection—whilst performing a build, Maven dynamically searches external repositories and downloads the required artifacts on the fly. By default, Maven looks for repositories that are accessed over the Internet. You can change this behavior so that Maven will prefer searching repositories that are on a local network.
    Note
    Maven can run in an offline mode. In offline mode Maven will only look for artifacts in its local repository.

Adding the Red Hat JBoss Fuse repository

In order to access artifacts from the Red Hat JBoss Fuse Maven repository, you need to add it to Maven's settings.xml file. Maven looks for your settings.xml file in the .m2 directory of the user's home directory. If there is not a user specified settings.xml file, Maven will use the system-level settings.xml file at M2_HOME/conf/settings.xml.
To add the JBoss Fuse repository to Maven's list of repositories, you can either create a new .m2/settings.xml file or modify the system-level settings. In the settings.xml file, add the repository element for the JBoss Fuse repository as shown in bold text in Example 3.2, “Adding the Red Hat JBoss Fuse Repositories to Maven”.

Example 3.2. Adding the Red Hat JBoss Fuse Repositories to Maven

<?xml version="1.0"?>
<settings>
    
  <profiles>
    <profile>
      <id>extra-repos</id>
      <activation>
        <activeByDefault>true</activeByDefault>
      </activation>
      <repositories>
       <repository>
            <id>redhat-ga-repository</id>
            <url>https://maven.repository.redhat.com/ga</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>redhat-ea-repository</id>
            <url>https://maven.repository.redhat.com/earlyaccess/all</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
        <repository>
          <id>jboss-public</id>
          <name>JBoss Public Repository Group</name>
          <url>https://repository.jboss.org/nexus/content/groups/public/</url>
        </repository>
      </repositories>
      <pluginRepositories>
        <pluginRepository>
            <id>redhat-ga-repository</id>
            <url>https://maven.repository.redhat.com/ga</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
        <pluginRepository>
            <id>redhat-ea-repository</id>
            <url>https://maven.repository.redhat.com/earlyaccess/all</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
        <pluginRepository>
          <id>jboss-public</id>
          <name>JBoss Public Repository Group</name>
          <url>https://repository.jboss.org/nexus/content/groups/public</url>
        </pluginRepository>
      </pluginRepositories>
    </profile>
  </profiles>
  
  <activeProfiles>
    <activeProfile>extra-repos</activeProfile>
  </activeProfiles>
    
</settings>

Artifacts

The basic building block in the Maven build system is an artifact. The output of an artifact, after performing a Maven build, is typically an archive, such as a JAR or a WAR.

Maven coordinates

A key aspect of Maven functionality is the ability to locate artifacts and manage the dependencies between them. Maven defines the location of an artifact using the system of Maven coordinates, which uniquely define the location of a particular artifact. A basic coordinate tuple has the form, {groupId, artifactId, version}. Sometimes Maven augments the basic set of coordinates with the additional coordinates, packaging and classifier. A tuple can be written with the basic coordinates, or with the additional packaging coordinate, or with the addition of both the packaging and classifier coordinates, as follows:
groupdId:artifactId:version
groupdId:artifactId:packaging:version
groupdId:artifactId:packaging:classifier:version
Each coordinate can be explained as follows:
groupdId
Defines a scope for the name of the artifact. You would typically use all or part of a package name as a group ID—for example, org.fusesource.example.
artifactId
Defines the artifact name (relative to the group ID).
version
Specifies the artifact's version. A version number can have up to four parts: n.n.n.n, where the last part of the version number can contain non-numeric characters (for example, the last part of 1.0-SNAPSHOT is the alphanumeric substring, 0-SNAPSHOT).
packaging
Defines the packaged entity that is produced when you build the project. For OSGi projects, the packaging is bundle. The default value is jar.
classifier
Enables you to distinguish between artifacts that were built from the same POM, but have different content.
The group ID, artifact ID, packaging, and version are defined by the corresponding elements in an artifact's POM file. For example:
<project ... >
  ...
  <groupId>org.fusesource.example</groupId>
  <artifactId>bundle-demo</artifactId>
  <packaging>bundle</packaging>
  <version>1.0-SNAPSHOT</version>
  ...
</project>
For example, to define a dependency on the preceding artifact, you could add the following dependency element to a POM:
<project ... >
  ...
  <dependencies>
    <dependency>
      <groupId>org.fusesource.example</groupId>
      <artifactId>bundle-demo</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>
  </dependencies>
  ...
</project>
Note
It is not necessary to specify the bundle package type in the preceding dependency, because a bundle is just a particular kind of JAR file and jar is the default Maven package type. If you do need to specify the packaging type explicitly in a dependency, however, you can use the type element.