APACHE MAVEN 3.X Will it live up to its promises?

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Arnaud Héritier •  eXo - Software Factory Manager

»  In charge of tools and methods

•  Apache Maven : »  Committer since 2004 and member of the

Project Management Committee

•  Coauthor of « Apache Maven » » published by Pearson (in French)

•  Contact me : » http://aheritier.net » Twitter : @aheritier » Skype : aheritier

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Definition

•  Apache Maven is a software project management and comprehension tool.

•  Based on the concept of a project object model (POM) » Maven can manage a project's build, binaries,

reporting and documentation from a central piece of information.

•  Apache Maven is standards/conventions driven » How many of you are doing JEE and related

developments ?

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History

•  Initiated in 2001 by Jason Van Zyl in Alexandria, an Apache Jakarta project,

•  Moved to Turbine few months after, •  Became a Top Level Project in 2003. •  Maven 2.0 released in September 2005 •  Maven 3.0 released in October 2010

» 3.0.3 – March 2011

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Choose your way of thinking

Conventions approach Scripting approach

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Competitors

•  Ant + Ivy, Easy Ant, Gant, Gradle, Buildr… •  Script oriented

» You can do what you want ! •  Reuse many of Maven conventions (directories layout,

…) and services (repositories) but without enforcing them

•  The risk for them : Not being able to evolve due to the too high level of customization proposed to the user. » We tried on Maven 1 and it died because of that. It was

impossible to create a set of tests to cover all usages. »  It’s like providing a framework without a well tested set of

public API

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With scripts oriented builds

You can have (if you have good skills)

But often you have (moreover after years …)

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With Maven

We dream to deliver (Maven 3.x)

But yesterday we too often had (Maven 2.x)

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BACKWARD COMPATIBILITY Apache Maven 3.x

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Backward compatibility - Criticisms

•  Migration from Maven 1 to Maven 2 was impossible. Everything had to be re-done.

•  Updates between 2.x versions and also between 2.0.x weren’t often without side effects.

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Backward compatibility

•  Near to 700 integration tests •  Tested for several months on a large set of

OSS projects •  7 alphas + 3 betas versions •  A bug fix release every 6 weeks •  It’s a revolution under the hood but an

evolution for end users

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Maven 3.0.x ITs

674

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PERFORMANCES Apache Maven 3.x

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Performances - Criticisms

•  Maven is slow •  It spends its time to download the world •  Whereas everybody has multicore CPUs, it

doesn’t allow to process modules builds in parallel

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Performances

•  A set of benchmark tools was developed to measure Maven performances (IO, CPU, Memory, Network …)

•  Startup and execution times are reduced » Java 5 optimizations » Code cleanup and improvements

•  Reduced Memory footprint •  Artifacts Resolution Caching

» .lastUpdated files in your local repo » Enforce checks with –U option

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Performances – Parallel builds

•  Parallel builds » An execution plan is predefined at startup to

define which modules could be built in // » Requires to have up to date plugins to avoid dead

locks and some others issues » Launch a build with 2 threads

•  mvn –T 2 install

» Launch a build with 2 threads per CPU core •  mvn –T 2C install

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Performances – mvnsh

•  Performances optimizations » Intelligent cache system (artifacts resolution,

project descriptors …) » No need to restart a JVM for each build

•  Cross platform « unix like » shell » Alias, environment settings … » Color highlighting

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Performances – mvnsh

•  All in one » Includes Maven 3.x » Allows to have color highlighting with “standard”

Maven 3.x •  Developed and freely distributed by Sonatype

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Performances – mvnsh

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EXTENSIBILITY Apache Maven 3.x

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Extensibility - Criticisms

•  It is difficult and time consuming to extend maven (write plugins) » Many unknown technologies like Plexus for IOC

•  It is difficult/impossible to reuse maven plugins » Its impossible to extend plugins/mojo and

lifecycles

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Extensibility

•  New APIs to improve abstraction of underneath implementation » Aether : to manage artifacts and repositories

•  Plugin classloader partitioning •  Embeddable •  IOC replaced by Guice

» For now (3.0) a wrapper is hiding the change » You don’t yet use Guice directly (from plugins for

example)

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ROBUSTNESS Apache Maven 3.x

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Robustness - Criticisms

•  Builds aren’t predictable •  Errors are difficult to diagnose

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Robustness - Validations

•  Many more validations in POMs (warnings or errors) » Missing plugins versions » Duplicated dependencies in a POM » Incoherent inheritance (wrong relative path or

parent not in the upper directory) •  Improved error messages with links to wiki

pages for more detailed information

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Robustness – Artifacts management

•  Parent POMs prefer to resolve from repositories » Version less parent will be available in a future

maven 3.x release by using the relativePath element

•  Profiles usage consolidation » No more profiles.xml (incompatible with future

polyglot feature)

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Robustness – Artifacts management

•  No more support for legacy repository layout for Maven 1.0

•  SNAPSHOTs are always deployed with timestamps

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Robustness – Plugins management

•  Plugin version is by default RELEASE and no more SNAPSHOT » Affects command-line invocation

•  Plugins cannot use versions LATEST or RELEASE » Affects command-line invocation and POM

•  Plugins are resolved only from <pluginRepository> entries

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Robustness – Site plugin

•  Site plugin is now completely extracted from Maven core » It has its own lifecycle » reporting section in POM becomes useless

(moved in plugin configuration)

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POM Apache Maven 3.x

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Criticisms

•  XML, we don’t like it •  POM is too verbose •  POM v4 didn’t evolve last 5 years

» When will you add new common attributes to ease plugins configuration (encoding …)

» New feature like global exclusions

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POM

•  No change in POM syntax for Maven 3.0 •  Changes will occur in 3.x versions

» New model with a new version » Only new things » Generation / deployment of 4.0.0 current POM to

keep backward compatibility with old maven versions

•  Mixins to allow to import POM fragments

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POM - Polyglot

•  Developed and freely distributed by Sonatype •  Extended version of Maven 3.0 using its new

embedding and extensibility capabilities •  Allow translation (read/write) from/to various

syntaxes » Yaml » Scala » Groovy

•  Allow macros and freeform scripting

TO GO FURTHER … Apache Maven

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IDE Apache Maven

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Eclipse

•  Integration from maven (eclipse:eclipse) » Allow many customizations » Support many versions/variants of eclipse » Support many usages (ear …) » Doesn’t support projects with “pom” packaging » Few support from dev team » Many bugs in classpath management » Asynchronous

•  You have to regenerate and reload project each time you change a POM)

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Eclipse

•  Integration from eclipse (m2eclipse) » Synchronous » Nice UI and services to edit POMs » Support projects with “pom” packaging » Doesn’t support all usages like EAR with WTP » Doesn’t support very well a large number of

modules » Slow down eclipse on large projects because of a

lack of support of incremental build in Maven 2.x and its plugins

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Eclipse (m2eclipse)

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Eclipse (m2eclipse)

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Eclipse (m2eclipse)

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Idea IntelliJ

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Netbeans

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COMMUNITY Apache Maven

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Users Mailing List

•  Blue : » Number of subscribers

•  Red : » Number of messages

per day

•  users@maven.apache.org » Traffic statistics cover a

total of 2025 days. » Current subscribers: 1936 » Current digest

subscribers: 48 » Total posts (2025 days):

89687 » Mean posts per day:

44.29 •  http://pulse.apache.org/

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Apache Maven Web Site

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Dowloads

Per month downloads http://people.apache.org/~vgritsenko/stats/

projects/maven.html

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The team

•  60 committers, •  More than 30 active in 2009, •  Several organizations like Sonatype, deliver

resources and professional support, •  A community less isolated : more interactions

with Eclipse, Jetty,

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Commit Statistics

•  In light blue the number of active commiters

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DOCUMENTATIONS Apache Maven

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Some links

•  The main web site : » http://maven.apache.org

•  Project’s team wiki : » http://docs.codehaus.org/display/MAVEN

•  Project’s users wiki : » http://docs.codehaus.org/display/MAVENUSER

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Books

•  Nicolas De loof Arnaud Héritier » Published by Pearson » Collection Référence » Based on our own

experiences with Maven.

» From beginners to experts.

» In French only

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Books

•  Sonatype / O’Reilly : » The Definitive Guide » http://

www.sonatype.com/books

» Free download » Available in several

languages

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Books

•  Apache Maven 2 Effective Implementation » Brett Porter, Maria

Odea Ching » https://

www.packtpub.com/apache-maven-2-effective-implementation/book

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Books

•  Exist Global » Better builds with

Maven » http://

www.maestrodev.com/better-build-maven

» Free download

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SUPPORT Apache Maven

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Support

•  Mailing lists » http://maven.apache.org/mail-lists.html

•  IRC » irc.codehaus.org - #maven

•  Forums » http://www.developpez.net/ forum maven » In French

•  Dedicated support » Sonatype and many others companies

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QUESTIONS ? Apache Maven

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Licence et copyrights

•  Photos and logos belong to their respective authors/owners

•  Various ideas are coming from the excellent presentation done by Matthew McCullough : » http://www.slideshare.net/matthewmccullough/

maven-30-at-oredev

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Licence et copyrights

•  Content under Creative Commons 3.0 » Attribution — You must attribute the work in the manner

specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work).

» Noncommercial — You may not use this work for commercial purposes.

» Share Alike — If you alter, transform, or build upon this work, you may distribute the resulting work only under the same or similar license to this one.

•  http://creativecommons.org/licenses/by-nc-sa/3.0/us/