The Maven2 Revolution Project Development Approach

The Maven2 Revolution

A new approach to project
development

Dror Bereznitsky
AlphaCSP

Copyright AlphaCSP Israel 2006 - The Ultimate Development Environment Seminar

Agenda

• What is Maven?
• Core Concepts of Maven 2
– Project Object Model
– The Build Lifecycle
– Maven Plugins
– The dependency Mechanism
– Repositories
• Maven vs. Ant

Copyright AlphaCSP Israel 2006 - The Ultimate Development Environment Seminar Page 2

What is Maven ?


A Build Survey

How much time do you spend creating and
managing your build files?
How many times have you created a new
build script from scratch?
Can someone new to your project can
immediately build, test, deploy it without
looking at documentation?


A Build Survey

If you answered :
1. Too much time
2. More than I can remember
3. No way
you are probably not working with


What is Maven?

A new approach to project development
• Configure your build don’t script it
• Define what to build not how
• Reuse of build logic
• Coherent Organization of Dependencies

A development tool – not building blocks


Maven’s Primary Goal

What is Maven’s project goal ?

Maven's primary goal is
to allow a developer to
understand the complete
state of a project
in the shortest period of time


The Primary Goal ..

The way to achieve this goal is:

• Making the build process easy
• Providing a uniform build system
• Providing guidelines for
best practices development
• Providing quality project information


Main Features

• Superior dependency management
• A large repository of libraries and metadata
• Multiple projects handling
• Extensible, easy to write plugins
• Coherent site of project information
• Release management and distribution
publication
• Multiple language support – C++, Java …


Core Concepts of Maven 2


Project Object Model

Define What, not How
• All the information required for the build is
contained in a single POM,
“Project Object Model”, XML file

• The developer provides information about
what is being built and not how


Project Object Model ..

The POM contains detailed METADATA
information about the project:
– Versioning and configuration management
– Dependencies
– Project structure
– Application and testing resources

And much more …


A POM Example

All the information required for the build in a single file
1 <project>
2 <modelVersion>4.0.0</modelVersion>
3 <groupId>com.alphacsp</groupId>
4 <artifactId>my-app</artifactId>
5 <packaging>jar</packaging>
6 <version>1.0-SNAPSHOT</version>
7 <dependencies>
8 <dependency>
9 <groupId>junit</groupId>
10 <artifactId>junit</artifactId>
11 <version>3.8.1</version>
12 <scope>test</scope>
13 </dependency>
14 </dependencies>
15 </project>


The Super POM

How this is possible using a 15 line file?

• Maven's implicitly use its Super POM
• Super POM carries with it all the default
conventions that Maven encourages
• Super POM is the parent of all POMs
• Analog of the Java language's
java.lang.Object class.


The Super POM ..


Standard Directory Layout

• A common directory
layout –
immediately feel at home
in any Maven project
• Based on best practices
• Simplifies the POM
• Can be created using
Archetypes


The Build Lifecycle

• Software projects generally follow similar
build paths: preparation, compilation,
testing, packaging, installation, etc.

• Maven2 is based around the central concept
of a build lifecycle – the process for
building and distributing a particular artifact
is clearly defined


Phases and Goals

The build life cycle consists of a series of phases
where each phase can perform one or more
actions, or goals

compile test

deploy package

install

The Build Lifecycle

The lifecycle phase invokes the plugins it needs to
complete its task and other dependant lifecycles


The 80/20 Rule

• Using the default lifecycle mapping, Maven
can build a basic project with little or no
modification – 80% case
• in certain circumstances, a project requires
special tasks in order to build successfully
• Maven can integrate these custom tasks
into the build process through its
extensible plugin framework.


Maven Plugins

Maven is actually a platform that executes
plugins within a build life cycle in order to
perform the build tasks


Maven Plugins ..

• With most projects, the plugins provided
“out of the box” by Maven are enough.
• More plugins can be found at the Apache
Maven Project and CodeHaus Mojo project.
• If needed, you can write custom plugins to
perform special build tasks.


Maven Mojo

“mojo” – maven old java object

• Plug-in developers only need to make
their individual goal, “mojo”, perform a
single task.

• A “mojo” has a set of inputs and
outputs.

• Plug-ins consist of one or more “mojos”

Mojo Example


Maven-Anno-Mojo

Let you use java 5.0 annotations syntax
instead of doclets for writing your mojos


Maven-Anno-Mojo ..

• Inheritance between plugins
• All the benefits of Java 5.0 – generics,
autoboxing …
• Delegation of execution to POJOs
• Natural Ant java tasks integration – not XML
based


The Dependency Mechanism

Maven excels in dependency management

• Transitive dependencies
• Dependency Scope
• Dependency Management
• Dependency exclusion


The Dependency Mechanism ..

Just Define your dependencies and forget about
them - maven will do the rest for you:

• Download the dependency
• Resolve all transient dependencies
• Add dependencies to compilation and test
classpath/include path
• Bundle dependencies when needed


The Dependency Mechanism …


Maven 2 Repositories

Maven repositories
shares the same
hierarchical structure
that hold the build
artifacts –
• Group
• Artifact
• Version


Maven 2 Repositories ..

There are two types of repositories:
• Remote - any type of repository, accessed by a
variety of protocols (file://, http://...).
http://repo1.maven.org is the central repository

• Local - a local cache of the
remote downloads and the latest build artifacts
Usually at : ${user.home}/.m2/repository


Remote Repository


Local Repository


Site Generation

Maven is famous for its
Site generation that
includes:
a reference to the build
server
Javadoc
source XRef
issue tracking reference
test and quality reports

Site examples – code coverage


Site examples – Surefire report


Site – Custom Look & Feel


IDE Support

Maven has some neat plug-ins for IDE project
generation, including:

– IntelliJ IDEA
– Eclipse
– Netbeans


IDE Support ..

• The IDE projects created include:
– All the dependencies 3rd party/internal
– Dependency source linking

• The created project is ready to compile, test
, debug and run.


Multiple Language Support

• Maven supports
multiple development
languages such as
Java , C++, C, C#,
Fortran and more.
• Different languages
has their own
common standard
layout.


Maven vs. Ant


Maven vs. Ant

OK, but Ant is working fine !

•Ant provides building blocks for a toolset - Maven
provides a working tool
•Ant has no build lifecycle, repositories, standard
project layout, dependency management …
you have to do it by yourself !
•Ant scripts become complex
•Ant scripts are not reusable – promotes duplication
•Ant is becoming legacy and not moving fast ahead

MyApp – Ant Build File – 141 lines

141 Lines of code !!!


MyApp - Maven Build File – 17 lines

17 Lines of code


Maven vs. Ant ..

From our experience in Ant migration
projects there is a 1:30 ratio in
the number of lines of code
between Maven2 and Ant.


Your Turn Now

Q&A


The Maven2 Revolution Project Development Approach

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