An Introduction to Maven

An Introduction to Maven
An Introduction to Apache Author: Vadim Lotar (QC Backend) 2011
Agenda  Automation Build Tool  A bit of history  Why Maven?  An Introduction to Maven  Drawbacks of Maven  Best practices  Maven in software development suite  Examples  Q&A
Automation Build Tool  Since the early days of modern engineering, automation of build processes has been the key to:  Productivity improvements  Quality insurance  Eliminate dependencies on key personnel  Save time and money  Why would software development be any different?
Automation Build Tool  How do you really enable automation of build?  Build has to be reproducible  Build has to produce the final production artifact  Build has to be as easy to maintain as possible and well documented
A bit of history  A simple script (.sh, .bat) is already a possible solution  More advanced command-line tools have been available for a long time  make created in 1977 at Bells Labs by Stuart Feldman. Still very much used nowadays  Apache Ant created by James Duncan Davidson
A bit of history Two main categories in current tools:  Scripting tools  Ant  Rake (Ruby based)  Gradle (Groovy based)  … many others  Artifact oriented tools  Maven  Debian Package Creation
A bit of history  Maven 1.x is now almost 12 years old project, mostly motionless since 2007 (I cannot find anybody still using it or committing to it)  Maven 2.x was the de facto standard for Java and Java EE build  Most open source projects were switched to Maven for their build system  It’s now seven years old  Maven 3.x is used in > 90% of Java (EE) startup applications.  It’s now two years old  Last release – ver. 3.0.3
Why Maven?  If you are not already using it:  Now is the best moment to start being aware  Maven is mature  Maven is getting better and better  Maven can be used online and offline  If you are already using it:  Hang on! The best is yet to come!  Focus on necessary things and don’t get frustrated by petty details
An Introduction to Maven Maven is a tool with multiple facets:  a BUILD tool  a DEPENDENCY MANAGEMENT tool  a DOCUMENTATION tool
An Introduction to Maven Project Object Model pom.xml Maven’s working …  Generated artifacts (jar, war, ear…),  Documentation, statistics (test results, quality metrics, javadoc, web site)…
An Introduction to Maven  A project can easily be cut into modules thanks to Maven  By simply declaring project metadata and optionally configuring a few plug-ins, you can:  Build your project (compile, generate sources…)  Launch tests and gather results (Junit, TestNG, Selenium…etc)  Package (Jar, War, Ejb, War…etc)  Document and generate reports
An Introduction to Maven Project Object Model (POM)  Basic project information  groupId, artifactId, version…  Inheritance, or Aggregation through sub-modules (will explain the difference later on)  Build section  Project layout (sources and resources folders… etc)  Build plugins configuration  Reporting section  Reports configuration  Some other advanced environment settings
An Introduction to Maven  A plug-in is made of a MOJO (Maven POJO) which is simply a java class with Maven- specific metadata.  A plug-in can define goals and reports  Goals can be called directly:  mvn plugin:goal  Goals can be bound to one or multiple phases  Reports are used during site generation  mvn site
An Introduction to Maven  When you invoke a phase, Maven will go through all the phases until the one specified, executing the bound goals:  mvn package
An Introduction to Maven  There are many more phases than in previous examples in the default lifecycle  By default, all the basic necessary plug-ins for the build phase are already bound to phases  It is easy to have information about plugins:  mvn help:describe  So….. what’s left to do, and what’s all the fuss about the complexity of Maven?
An Introduction to Maven Dependencies: A blessing and a curse  Blessing:  Transitive dependencies  easier to find/discover/use java libraries  Curse:  Transitive dependencies can rapidly trigger a dependency hell!  Harder to stabilize builds
An Introduction to Maven  What really made Maven different from other builds systems in the first place?  REPOSITORIES!!!  Before Maven, it was really hard to find java libraries, and harder to ensure a coherent use of these libraries  Nowadays, it’s still very hard to find some jars with a decent/coherent versioning, let alone to find their sources or javadocs
An Introduction to Maven  Local repository:  Local cache for artifacts  Contain temporary build artifacts  It’s possible to erase it regularly  Very useful for offline builds  By default in user home’s .m2/repository folder  Can be moved to another place through Maven runtime’ settings.xml file  $MAVEN_HOME/conf/settings.xml
An Introduction to Maven  Corporate repository/proxy  Access via file:// and http://  The first necessary step towards a corporate use of maven  The local and remote repositories are structured the same  Even better: install a repository management tool  Can proxy external repositories  Can filter unwanted artifacts
An Introduction to Maven  Public repositories  Good for dependencies’ harvesting  A lot of mis-configured dependencies  A lot of alpha/beta Maven plugins and libraries  Be cautious when adding public repositories to a build process!  Should be proxied in corporate
An Introduction to Maven Other key features of Maven:  POM Inheritance/Aggregation  Archetypes  Launching Tests  … many more…
An Introduction to Maven  POM – Project Object Model  Super POM  Inheritance  Aggregation  Inheritance vs Aggregation
An Introduction to Maven Project Archetypes  You can build template projects and make them available as artifacts in the repositories  mvn archetype:create-from-project  Allows to share best practices without neither inheritance nor aggregation  mvn archetype:generate  Many Archetypes already configured in the default catalog  You can easily build a custom or corporate catalog mvn archetype:generate –DarchetypeCatalog=http://www.corporate.com/archetypes.xml
An Introduction to Maven Archetype ArtifactIds Description maven-archetype-archetype An archetype which contains a sample archetype. maven-archetype-j2ee-simple An archetype which contains a simplifed sample J2EE application. maven-archetype-mojo An archetype which contains a sample a sample Maven plugin. maven-archetype-plugin An archetype which contains a sample Maven plugin. maven-archetype-plugin-site An archetype which contains a sample Maven plugin site. maven-archetype-portlet An archetype which contains a sample JSR-268 Portlet. maven-archetype-quickstart An archetype which contains a sample Maven project. maven-archetype-simple An archetype which contains a simple Maven project. maven-archetype-site An archetype which contains a sample Maven site which demonstrates some of the supported document types like APT, XDoc, and FML and demonstrates how to i18n your site. maven-archetype-site-simple An archetype which contains a sample Maven site. maven-archetype-webapp An archetype which contains a sample Maven Webapp project.
An Introduction to Maven Launching Tests  Maven allows to launch various types of tests:  Unit tests: Junit 3.x or 4.x, TestNG, …  UI Tests: Selenium, Canoo Webtest  Functional tests: Fitnesse, Greenpepper  WebServices tests: SOAPUi  And many more…
Drawbacks of Maven  Library repositories are not always safe.  Maven Conventions  Hard to find some things about maven and plugins  A huge output log  Sequential build (Lyfecycle)  Learning Maven is long in comparison of Ant.
Best practices  Embrace the standardization brought by Maven, don’t fight it  Use POM Inheritance and <dependencyManagement> (with import scope), <pluginManagement>  Use a Repository Manager:  Sonatype Nexus: http://nexus.sonatype.org  Jfrog Artifactory: http://artifactory.jfrog.org  …
Best practices  Keep your build as simple as possible  Launch your builds regularly and possibly in a neutral zone  Use the “dependency” and “versions” plugins  Generate test statistics data and other metrics data in order to exploit them in Software quality tools:  Sonar: http://sonar.codehaus.org  Squale: http://www.squale.org  …
Maven in a Software development suite  Maven is now very well integrated in IDEs  NetBeans 6.5+ now has very good support for Maven  Eclipse 3.x has very good support also.  IntelliJ IDEA seems to have excellent support also (though this is why you pay for it isn’t it?)  Maven works very well with Quality monitoring tools  Continuous integration
References and Thanks Documentation and information:  Site http://maven.apache.org  Plugins  http://maven.apache.org/plugins  http://mojo.codehaus.org/  http://code.google.com/  And many others…  Project Wiki http://docs.codehaus.org/display/MAVEN/  Users’ Wiki http://docs.codehaus.org/display/MAVENUSER
References and Thanks Books  Free electronic editions:  Definitive Guide: http://www.sonatype.com/books  Better Builds with Maven: http://www.maestrodev.com/better-build-maven  Upcoming book by Arnaud Héritier and Nicolas De Loof http://www.pearson.fr/livre/?GCOI=27440100730370 Thanks  Many thanks to Pierre-Antoine Grégoire for its presentation on YaJUG  Thanks to Jason van Zyl for its Maven 3 presentation http://www.sonatype.com/people/author/jason

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