Maven 2 features

A Pragmatic View Presentation by Angel Ruiz Calvo

Index
What is Maven 2?
What does it provide?
Comparison with Ant.
Examples.
Installation.
Conclusions.
References.
Questions.

What is Maven 2?

Formal definition:
“ Maven is a project management tool which encompasses a project object model, a set of standards, a project lifecycle, a dependency management system, and logic for executing plug-in goals at defined phases in a lifecycle. When you use Maven, you describe your project using a well-defined project object model, Maven can then apply cross-cutting logic from a set of shared (or custom) plug-ins”.
My definition:
It is a project management tool that helps us in all the stages of the SDLC applying the principle of “Convention over Configuration” that simplifies many common issues involved in the development of any project.
What is Maven 2?

Convention over configuration:
Systems, libraries, and frameworks should assume reasonable defaults without requiring unnecessary configuration to " just work ".
Under this premise it provides:
Conceptual model of a project: P.O.M.
Plug-in based extensibility.
Standard project structure
Standard project identification.
Dependency Management
Repository Management
Project initialization: Archetypes.
IDE Portability and Integration.
Project configuration (JDK compilation level, SCM, Bug tracking, mailing lists, developers …).
Simplify and unify the process for documentation distribution and maintenance.

P.O.M. = Project Object Model.
Maven projects are describes using a single file called pom.xml
This conceptual model is described using an XMLSchema.
Within this P.O.M. file you can define the following project information:
General project info: name, artifact, …
Customized configuration for each SDLC step: packaging, jdk, …
Dependencies.
External tools:
Mailing lists.
S.C,M. tool.
Bug tracking
Repository configuration: usually delegated on settings.xml file
…

Plug-in based extensibility
Maven has been designed to delegate most responsibility to a set of Maven Plugins which can affect the Maven Lifecycle and offer access to goals.
mvn war:war
Plug-in name Goal

The Maven Lifecycle.

The real value.
Plug-ins Core
Clean
Compiler
Deploy
Install
Resources
Site
Surefire
Verifier
…
Tools
Ant
Antlr
Antrun
Archetype
Assembly
Help
Release
SCM
XDoclet
…
Changelog
Changes
Checkstyle
Clover
Javadocs
PMD
Surefire-reports
…
Reporting
Cargo
Jaxme
Jetty
Tomcat
…
Ear
Ejb
Jar
Rar
War
…
Eclipse
IDEA
…
Others Packaging Integration

Standard project structure :
Flexible.
Clean
Standard.
Easy to understand.

Standard project identification
Artifact = maven project coordinates
Essential for dependency management.
<project> <modelVersion>4.0.0</modelVersion> <groupId> au.com.sra </groupId> <artifactId> sra.commons </artifactId> <version> 0.0.1-SNAPSHOT </version> </project> groupId artifactId version

Versioning nomenclature system:
X Y Z This identifier is used when the project is currently under active development . artifactId version Package (JAR / WAR / EAR) sra-commons - 0.0.1 - SNAPSHOT .jar
Bugfixes
Minor: fixes and adds
Mayor: no backward compatibility

How can we look for artifacts: http:// www.mvnrepository.com /

Based on maven project coordinates.
It also implies a new and important parameter called Dependency Scope
<project> … <dependencies> <dependency> <groupId> au.com.sra </groupId> <artifactId> sra.commons </artifactId> <version> 0.0.1-SNAPSHOT </version> <scope> compile </scope> </dependency> … </dependencies> </project>
compile (default)
provided
runtime
test
system

There are some other concepts regarding dependency management:
Transitive dependencies:
Optional dependencies:
Conflict resolution and dependency exclusion:
Dependency version range:
Multi-module projects:
Dependency A Dependency B Dependency C

With this feature you won’t have to maintain all the libs you are using in your SCM tool and you will reference them from a single common point.
By default Maven uses a local repository that is fed from the Maven Central repository or any other public Maven repository on the Internet, you may have configured in your settings.xml file.
By default this local repository is at ${user_home}/.m2/repository , but it is configurable.
In order to avoid multiple internet access to download the same file and also to get faster download speed we will use a Repository Manager that acts like a proxy between our office and the public Maven repositories.
It also provides a good platform to have all the company releases available and well identified.

The chosen repository management tool is called NEXUS from Sonatype: http://actdec01:8081/nexus

Project initialization: Archetypes
An archetype is a template for a Maven project which is used by the Maven Archetype plug-in to create new projects.
Archetypes can also be useful within an organization that wants to encourage standards across a series of similar and related projects.
mvn archetype:create -DgroupId=org.apache.maven.archetypes
-DartifactId=maven-archetype-webapp

IDE Portability and Integration
Tools like Eclipse, NetBeans, and IntelliJ now have a common place to find information about a project. Before the advent of Maven, every IDE had a different way to store what was essentially a custom Project Object Model (POM). Maven has standardized this description, and while each IDE continues to maintain custom project files, they can be easily generated from the model.
Integration can be performed in both ways:
Maven plugin:
IDE plugin:
mvn eclipse:eclipse
Built-in plug-in Built-in plug-in

Simplify and unify the process for documentation distribution and maintenance
Maven site plug-in + reports

Comparison with Ant

Comparison with Ant
Two complementary tools
Maven is definitely better for all the tasks related to the project building process.
Ant is better for all the rest programmatic tasks.
Maven has conventions, it already knew where your source code was because you followed the convention. It put the bytecode in target/classes, and it produced a JAR file in target. Ant doesn't have formal conventions like a common project directory structure, you have to tell Ant exactly where to find the source and where to put the output. Informal conventions have emerged over time, but they haven't been codified into the product. Maven has a lifecycle, which you invoked when you executed mvn install. This command told Maven to execute the a series of sequence steps until it reached the lifecycle. As a side-effect of this journey through the lifecycle, Maven executed a number of default plugin goals which did things like compile and create a JAR. Ant doesn't have a lifecycle, you had to define goals and goal dependencies. You had to attach a sequence of tasks to each goal manually Maven is declarative . All you had to do was create a pom.xml file and put your source in the default directory. Maven took care of the rest. Ant is procedural , you have to tell Ant exactly hat to do and when to do it. You had to tell it to compile, then copy, then compress …

Comparison with Ant
Comparison thorough and example to build a jar file
mvn package

Examples

Installation

Installation
Steps to install Maven
Download the latest version of Maven (currently is 2.0.9).
Unzip the file.
Put the bin folder into the system path variable.
Execute the following command to check that the mvn command is available:
Download the latest settings.xml file from the SRA wiki and place it at ${user_home}/.m2
The repository will be at C:.m2 epository
You also can find this instructions at the SRA Wiki.
mvn -version

Conclusions

Conclusions
Do not spend too much time defining procedures that are already modeled in Maven.
Maven is the result of many experienced professionals.
Maven is unquestionably linked to the following concepts:
methodology standarization productivity agility usability quality control

References

References
Maven portal
Maven: The definitive guide
Better builds with Maven
m2Eclipse plug-in

Questions

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Maven 2 features

by Angel Ruiz on Dec 03, 2008

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Maven 2 features — Presentation Transcript