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Mastering Apache Maven 3

By : Siriwardena

4.3 (3)

Mastering Apache Maven 3

4.3 (3)

By: Siriwardena

Overview of this book

If you are working with Java or Java EE projects and you want to take full advantage of Maven in designing, executing, and maintaining your build system for optimal developer productivity, then this book is ideal for you. You should be well versed with Maven and its basic functionality if you wish to get the most out of the book.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Apache Maven Quick Start

1. Apache Maven Quick Start

A quick introduction

Installing Apache Maven

Configuring the heap size

Monitoring the build

Remote debugging

Convention over configuration

IDE integration

Troubleshooting

Summary

2. Demystifying Project Object Model

2. Demystifying Project Object Model

Project Object Model

The POM hierarchy

Super POM

POM extending and overriding

Maven coordinates

Parent POM file

Managing POM dependencies

Summary

3. Maven Configuration

3. Maven Configuration

Maven Wagon

Proxy authentication

Secured repositories

Encrypting credentials in settings.xml

Source Control Management systems

Local repository location

Mirrored repositories

Deploying artifacts

Enabling Maven logging

Summary

4. Build Lifecycles

4. Build Lifecycles

Standard lifecycles in Maven

Lifecycle bindings

Building a custom lifecycle

Lifecycle extensions

Summary

5. Maven Plugins

5. Maven Plugins

Common Maven plugins

Plugin discovery and execution

Plexus

Maven and Dependency Injection

Developing custom plugins

Summary

6. Maven Assemblies

6. Maven Assemblies

The assembly plugin

The assembly descriptor

Artifact/resource filtering

Assembly help

A runnable, standalone Maven project

Summary

7. Maven Archetypes

7. Maven Archetypes

Archetype quickstart

The batch mode

Archetype catalogues

The archetype plugin goals

Maven plugins with the archetype plugin

Java EE web applications with the archetype plugin

Android mobile applications with the archetype plugin

EJB archives with the archetype plugin

JIRA plugins with the archetype plugin

Spring MVC applications with the archetype plugin

Building a custom archetype

Summary

8. Maven Repository Management

8. Maven Repository Management

Maven repositories

The update policy

Multiple repositories

The Maven repository manager

Creating a proxy repository

Creating a virtual repository

Blocking selected artifacts

Inclusive and exclusive routing

Scheduled tasks

Artifact indexing

Nexus plugins

A repository metadata model

Summary

9. Best Practices

9. Best Practices

Dependency management

Defining a parent module

POM properties

Avoiding repetitive groupId and version tags and inherit from the parent POM

Following naming conventions

Maven profiles

Think twice before you write your own plugin

The Maven release plugin

The Maven enforcer plugin

Avoid using un-versioned plugins

Using exclusive and inclusive routes

Avoid having both release and snapshot repositories in the same group repository

Avoid having both proxy and hosted repositories in the same group repository

Minimizing the number of repositories

Using mirrorOf instead of changing repository URLs

Descriptive parent POM files

Documentation is your friend

Avoid overriding the default directory structure

Using SNAPSHOT versioning during development

Get rid of unused dependencies

Avoid keeping credentials in application POM files

Avoid using deprecated references

Avoid repetition – use archetypes

Avoid using maven.test.skip

Share resources – avoid duplicates

Summary

Index

Index

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Configuring the heap size

Once you have installed Maven in your system, the next step is to fine-tune it for optimal performance. By default, the maximum heap allocation is 256 - 512 MB (-Xms256m to -Xmx512m). This default limit does not work while building a large, complex Java project, and it is recommended that you have at least 1024 MB of maximum heap. If you encounter the java.lang.OutOfMemoryError error at any point during a Maven build, it is mostly due to the lack of memory. You can use the MAVEN_OPTS environment variable to set the maximum allowed heap size for Maven at a global level.

The following command will set the heap size in Linux. Make sure that the value set as the maximum heap size does not exceed your system memory of the machine that runs Maven.

$ export MAVEN_OPTS="-Xmx1024m -XX:MaxPermSize=128m"

If you are on Microsoft Windows, use the following command:

$ set MAVEN_OPTS=-Xmx1024m -XX:MaxPermSize=128m

Here -Xmx takes the maximum heap size and -XX:MaxPermSize takes the maximum PermGen size.

Note

Maven runs as a Java process on JVM. As Java proceeds with a build, it keeps on creating Java objects. These objects are stored in the memory allocated to Maven. This area of memory where Java objects are stored is known as heap. Heap is created at the JVM start, and it increases as more and more objects are created up to the defined maximum limit. The -Xms JVM flag is used to instruct JVM the minimum value it should set at the time it creates the heap. The -Xmx JVM flag sets the maximum heap size.

Permanent Generation (PermGen) is an area of memory managed by JVM, which stores the internal representations of Java classes. The maximum size of PermGen can be set by the -XX:MaxPermSize JVM flag.

To learn about the Maven OutOfMemoryError error, check out the information at this link: https://cwiki.apache.org/confluence/display/MAVEN/OutOfMemoryError.

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