pseudofish

I’ve been looking at build tools for JVM projects. These are the notes I took while reviewing Maven.

• mvn install
• mvn site - generate a summary of the project
• mvn dependency:analyze - determine missing or unused dependencies
• mvn dependency:tree - tree view of dependencies
• mvn help:effective-pom - useful for debugging

Refactoring Maven Projects

For a given Maven project, these are some strategies to optimise the process. Mostly this is the DRY principle - Don’t Repeat Yourself.

• Pull up common dependencies to “dependencyManagement”, then only refer to groupId:artifactId in the child project
• Use built-ins ${project.version} and ${project.groupId} when referring to a sibling project
• Use properties to re-factor version numbers across multiple dependencies from the same group

Build profiles

Use build profiles to setup different environments for dev/test/staging/production

• Specify profiles as the last things in a POM
• Call using -P e.g. mvn clean install -Pproduction -X
• Activation parameters automatically select a profile based on a set of selectors. (ie. a JDK6 profile if JDK6 is used)
• Profiles can be stored in a separate “profiles.xml” that lives next to “pom.xml”
• mvn help:active-profiles
• You can set a default profile in your ~/.m2/settings.xml and put passwords into settings files as well

Finding bundles

There is an online repository at http://mvnrepository.com/

Maven Properties

• project.* – Maven Project Object Model, that is stuff in your pom.xml. See: http://maven.apache.org/ref/2.2.1/maven-model/maven.html
• settings.* – Things from your \~/.m2/settings.xml file. See: online docs
• env.* – Environment variables, such as PATH, HOME, JAVA_HOME and M2_HOME. Note: prefer ${user.home} to ${env.HOME}
• System properties – things from System.getProperty(), such as java.version, java.home, os.name, os.arch, user.dir, user.home, etc.
• User defined – arbitrary properties within your pom.xml

Note: you can use maven properties in resource files, such as a .properties or .xml file under src/main/resources.

You need to enable this in the pom.xml:

<build>
  <resources>
    <resource>src/main/resources</resource>
    <filtering>true</filtering>
  </resources>
</build>

Assigning custom properties per profile can help with deployment into multiple environments.

Maven & Eclipse

Eclipse has very good integration for Maven. Later versions of Eclipse include this in their package. It can also be added from http://m2eclipse.codehaus.org/

Maven Archetypes

Archetypes exist for a range of different project types.

mvn archetype:generate

Custom archetypes can be developed if you have a new type of project or generated from an existing project.

Maven sites

Maven can generate a site for your project showing information about the project and various reports.

mvn archetype:create -DgroupId=com.example -DartifactId=sample-project
cd sample-project
mvn site:run
mvn clean site
mvn site:run
mvn clean site-deploy

Repository Manager

Hosting a local repository for a team provides a number of benefits, including a local cache to avoid excessive network usage. Additionally, work can be shared both internally and externally.

A repository can be as simple as a file system with the appropriate layout, or a full repository manager. Nexus is an option for hosting a repository. It can be downloaded from: http://nexus.sonatype.org/download-nexus.html

Other Resources

• Cheat sheet – comprehensive list of useful commands.
• Maven - The Definitive Guide
• Various Books
• Using Maven with Clojure

Note: I’m continuing with lein for my clojure projects. To integrate with Maven, you can generate a pom.xml file for a with “lein pom“.