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Maven Essentials
Maven Essentials

Maven Essentials: Get started with the essentials of Apache Maven and get your build automation system up and running quickly

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Profile Icon Russell E Gold Profile Icon Siriwardena
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$19.99 per month
Full star icon Full star icon Full star icon Half star icon Empty star icon 3.9 (8 Ratings)
Paperback Dec 2015 184 pages 1st Edition
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Arrow left icon
Profile Icon Russell E Gold Profile Icon Siriwardena
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$19.99 per month
Full star icon Full star icon Full star icon Half star icon Empty star icon 3.9 (8 Ratings)
Paperback Dec 2015 184 pages 1st Edition
eBook
€14.99 €16.99
Paperback
€20.99
Subscription
Free Trial
Renews at $19.99p/m
eBook
€14.99 €16.99
Paperback
€20.99
Subscription
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Renews at $19.99p/m

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Maven Essentials

Chapter 2. Understanding the Project Object Model (POM)

POM is at the heart of any Maven project. This chapter focuses on the core concepts and best practices related to POM in building a large-scale, multi-module Maven project.

As we proceed with this chapter, the following topics will be covered in detail:

  • The POM hierarchy, super POM, and parent POM
  • Extending and overriding POM files
  • Maven coordinates
  • Managing dependencies
  • Transitive dependencies
  • Dependency scopes and optional dependencies

Project Object Model (POM)

Any Maven project must have a pom.xml file. POM is the Maven project descriptor just like the web.xml file in your Java EE web application, or the build.xml file in your Ant project. The following code lists out all the key elements in a Maven pom.xml file. As we proceed with the book, we will discuss how to use each element in the most effective manner:

<project>

  <parent>...</parent>   

  <modelVersion>4.0.0</modelVersion>     
  <groupId>...</groupId>   
  <artifactId>...</artifactId>   
  <version>...</version>   
  <packaging>...</packaging>
   
  <name>...</name>   
  <description>...</description>   
  <url>...</url>   
  <inceptionYear>...</inceptionYear>   
  <licenses>...</licenses>   
  <organization>...</organization>   <developers>...</developers>   
  <contributors>...</contributors...

POM hierarchy

POM files maintain a parent-child relationship between them. A child POM file inherits all the configuration elements from its parent POM. Using this trick, Maven sticks to its design philosophy convention over configuration. The minimal POM configuration for any Maven project is extremely simple, which is as follows:

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.packt</groupId>
  <artifactId>sample-one</artifactId>
  <version>1.0.0</version>
</project>

Tip

Downloading the example code

You can download the example code files for all Packt books you have purchased from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.

Super POM

Any POM file can point to its parent POM. In case the parent POM element is missing, there is a system wide POM file that is automatically treated as the parent POM. This POM file is well known as the super POM. Ultimately, all the application POM files get extended from the super POM. The super POM file is at the top of the POM hierarchy and is bundled inside MAVEN_HOME/lib/maven-model-builder-3.3.3.jar - org/apache/maven/model/pom-4.0.0.xml. In Maven 2, this was bundled inside maven-2.X.X-uber.jar. All the default configurations are defined in the super POM file. Even the simplest form of a POM file will inherit all the configurations defined in the super POM file. Whatever configuration you need to override, you can do it by redefining the same section in your application POM file. The following lines of code show the super POM file configuration, which comes with Maven 3.3.3:

<project>
  <modelVersion>4.0.0</modelVersion>

The Maven central is the only repository...

POM extending and overriding

Let's see how POM overriding works. In the following example, we extend the repositories section to add one more repository than what is defined in the Maven super POM:

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.packt</groupId>
  <artifactId>sample-one</artifactId>
  <version>1.0.0</version>

  <repositories>
    <repository>
      <id>wso2-nexus</id>
      <name>WSO2 internal Repository</name> 
      <url>http://maven.wso2.org/nexus/content/
                                       groups/wso2-public/
      </url>
      <releases>
        <enabled>true</enabled>
        <updatePolicy>daily</updatePolicy>
        <checksumPolicy>ignore</checksumPolicy>
      </releases>
    </repository>
  </repositories>

</project>

Execute the following command from the directory where the...

Maven coordinates

Maven coordinates uniquely identify a project, dependency, or plugin defined in a POM. Each entity is uniquely identified by the combination of a group identifier, artifact identifier, and the version (and, of course, with the packaging and the classifier). The group identifier is a way of grouping different Maven artifacts. For example, a set of artifacts produced by a company can be grouped under the same group identifier. The artifact identifier is the way you identify an artifact, which could be a JAR, WAR, or any type of an artifact uniquely identified within a given group. The version element lets you keep the same artifact in different versions in the same repository.

Note

A valid Maven POM file must have groupId, artifactId, and version. The groupId and version elements can also be inherited from the parent POM.

All the three coordinates of a given Maven artifact are used to define its path in the Maven repository. If we take the following example, the corresponding...

Project Object Model (POM)


Any Maven project must have a pom.xml file. POM is the Maven project descriptor just like the web.xml file in your Java EE web application, or the build.xml file in your Ant project. The following code lists out all the key elements in a Maven pom.xml file. As we proceed with the book, we will discuss how to use each element in the most effective manner:

<project>

  <parent>...</parent>   

  <modelVersion>4.0.0</modelVersion>     
  <groupId>...</groupId>   
  <artifactId>...</artifactId>   
  <version>...</version>   
  <packaging>...</packaging>
   
  <name>...</name>   
  <description>...</description>   
  <url>...</url>   
  <inceptionYear>...</inceptionYear>   
  <licenses>...</licenses>   
  <organization>...</organization>   <developers>...</developers>   
  <contributors>...</contributors...

POM hierarchy


POM files maintain a parent-child relationship between them. A child POM file inherits all the configuration elements from its parent POM. Using this trick, Maven sticks to its design philosophy convention over configuration. The minimal POM configuration for any Maven project is extremely simple, which is as follows:

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.packt</groupId>
  <artifactId>sample-one</artifactId>
  <version>1.0.0</version>
</project>

Tip

Downloading the example code

You can download the example code files for all Packt books you have purchased from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.

Super POM


Any POM file can point to its parent POM. In case the parent POM element is missing, there is a system wide POM file that is automatically treated as the parent POM. This POM file is well known as the super POM. Ultimately, all the application POM files get extended from the super POM. The super POM file is at the top of the POM hierarchy and is bundled inside MAVEN_HOME/lib/maven-model-builder-3.3.3.jar - org/apache/maven/model/pom-4.0.0.xml. In Maven 2, this was bundled inside maven-2.X.X-uber.jar. All the default configurations are defined in the super POM file. Even the simplest form of a POM file will inherit all the configurations defined in the super POM file. Whatever configuration you need to override, you can do it by redefining the same section in your application POM file. The following lines of code show the super POM file configuration, which comes with Maven 3.3.3:

<project>
  <modelVersion>4.0.0</modelVersion>

The Maven central is the only repository...

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Key benefits

  • Explore the essentials of Apache Maven essentials to arm yourself with all the ingredients needed to develop a comprehensive build automation system
  • Identify the extension points in Apache Maven and learn more about them in-depth
  • Improve developer productivity by optimizing the build process with best practices in Maven using this compact guide

Description

Maven is the #1 build tool used by developers and it has been around for more than a decade. Maven stands out among other build tools due to its extremely extensible architecture, which is built on of the concept of convention over configuration. It’s widely used by many open source Java projects under Apache Software Foundation, Sourceforge, Google Code, and more. Maven Essentials is a fast-paced guide to show you the key concepts in Maven and build automation. We get started by introducing you to Maven and exploring its core concepts and architecture. Next, you will learn about and write a Project Object Model (POM) while creating your own Maven project. You will also find out how to create custom archetypes and plugins to establish the most common goals in build automation. After this, you’ll get to know how to design the build to prevent any maintenance nightmares, with proper dependency management. We then explore Maven build lifecycles and Maven assemblies. Finally, you will discover how to apply the best practices when designing a build system to improve developer productivity.

Who is this book for?

The book is ideal for for experienced developers who are already familiar with build automation, but want to learn how to use Maven and apply its concepts to the most difficult scenarios in build automation.

What you will learn

  • Comprehend the key concepts in Apache Maven
  • Build your own custom plugins and get to know how Maven extension points are used
  • Troubleshoot build issues with greater confidence
  • Optimize Maven's configuration settings
  • Write custom lifecycles and extensions
  • Get hands-on and create a Maven assembly
  • Explore the best practices to design a build system that improves developer productivity

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Dec 02, 2015
Length: 184 pages
Edition : 1st
Language : English
ISBN-13 : 9781783986767
Vendor :
Apache
Languages :
Tools :

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Product Details

Publication date : Dec 02, 2015
Length: 184 pages
Edition : 1st
Language : English
ISBN-13 : 9781783986767
Vendor :
Apache
Languages :
Tools :

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Table of Contents

8 Chapters
1. Apache Maven Quick Start Chevron down icon Chevron up icon
2. Understanding the Project Object Model (POM) Chevron down icon Chevron up icon
3. Maven Archetypes Chevron down icon Chevron up icon
4. Maven Plugins Chevron down icon Chevron up icon
5. Build Lifecycles Chevron down icon Chevron up icon
6. Maven Assemblies Chevron down icon Chevron up icon
7. Best Practices Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

Top Reviews
Rating distribution
Full star icon Full star icon Full star icon Half star icon Empty star icon 3.9
(8 Ratings)
5 star 37.5%
4 star 25%
3 star 25%
2 star 12.5%
1 star 0%
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Albert Dec 18, 2023
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Plugin chapter is gold!
Subscriber review Packt
ANTONIO MENDOZA Jan 26, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book is easy to read and to follow even for a non-native English speaker. Concepts are well explained with real examples, which helps understanding the pros and cons of each implementation.The book teaches you step by step what is Maven, its components, and how it works. From the installation, to best practices, through concepts as how to customise the process of building your project.The best chapters are the 4th and the 5th, that allowed me to understand how Maven lifecycle works and the role that Maven plugins play inside Maven.This book goes beyond key concepts of Maven, with interesting tricks like “Deploying web applications to a remote Apache Tomcat Server”.I definitely recommend this book both if you want to learn maven, and if you want to update and consolidate your knowledge.
Amazon Verified review Amazon
Angelo Jul 20, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Libro ben fatto, molto facile da leggere, con esempi pratici, veramente essential.Si legge velocemente e permette di avere subito strumenti a disposizione per poter cominciare.
Amazon Verified review Amazon
Alexander J Heim May 16, 2016
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
It is clearly written and makes learning Maven easy.
Amazon Verified review Amazon
Audun V. Nes Jun 28, 2016
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
I liked this one. Concepts are well explained, and many good examples.
Amazon Verified review Amazon
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