Apache Maven: Best Practices - Brett Porter

Apache Maven: Best Practices Brett Porter - [email protected] http://www.devzuz.org/blogs/bporter

Maven without the PAIN

Sometimes unpleasant You know it’s for your own good! Can avoid or alleviate the problems 2

Who am I? Apache Maven developer since 2003

Started the Archiva project

Co-author of Better Builds with Maven

Co-founder of DevZuz 3

Getting Ready for Maven 4

Why are you using Maven? Consider this from the beginning Right tool for the job Ensure you reap the benefits

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Planning Ahead Preparing Your Environment 6

Development Environment Maven is best used in the bigger picture Plan for the infrastructure you will use ... ... ...

... ...

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Automated Build Servers Maven is intended to be automated More than continuous integration

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Repository Management Centralise storage of artifacts Store the artifacts you build Store third-party artifacts you consume

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Repository Servers Can start with a simple storage Servers can help manage the artifacts

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Using Repositories apache-snapshots Apache Snapshots Repository http://people.apache.org/repo/m2-snapshot-repository false java-net-m1 Java.net Repository http://download.java.net/maven/1/ legacy false

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Using Repositories

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apache-releases Apache Releases Repository apache-snapshots http://people.apache.org/repo/m2-ibiblio-rsyncApache Snapshots Repository repository http://people.apache.org/repo/m2-snapshot-repository codehaus-snapshots Codehaus Snapshots Repository false false http://snapshots.repository.codehaus.org/ codehaus-releases false Codehaus Releases Repository http://repository.codehaus.org/ java-net-m1 Java.net Repository false java-net-m2 http://download.java.net/maven/1/ Java.net Repository legacy http://download.java.net/maven/2/ false false 12

Using Repositories Minimise the number of repositories Only in the POM if you redistribute Use repository manager to centralise

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Locking Down archiva-snapshots-apache http://reposerver/archiva/repository/snapshots/ apache.snapshots archiva-snapshots-codehaus http://reposerver/archiva/repository/snapshots/ codehaus.snapshots ... archiva-default http://reposerver/archiva/repository/internal/ *

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Settings and Installation Three levels of configuration project (pom.xml) user (~/.m2/settings.xml) installation (/conf/settings.xml)

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Keeping it Simple Creating New Projects 16

Archetypes Create new projects quickly Standard project layouts Include organisational POM Facilitates consistency

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Writing the POM Write the build like you write code Utilise conventions Use multiple modules

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Inheritance Multi-module inheritance org.apache.maven maven 2.1-SNAPSHOT maven-core

Organisational POM hierarchy org.apache apache 3 org.apache.maven maven 2.1-SNAPSHOT 19

Dependencies Specify only what you need Specify scope Use dependencyManagement to: coerce Maven to use a particular version enforce consistency within a project

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Build Pipeline Depends on your team Use profiles for controlling complexity Applies to testing as well Key is to keep the build fast

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Scripting Maven is declarative by design Integrate scripting if necessary Consider writing plugins

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The D Word Documenting as You Go 23

Documentation Document the build Developer documentation separate from product documentation keep it together with reports

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Sites and Reports A whole other topic of best practices! But apply the same principles set up what you’ll actually use set up enforcement checks, not just reports

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Portability Playing with Others 26

The Goal When a new developer builds the project it works first go ... and it keeps working

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maven.test.skip is evil

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Hard Coding Don’t hard code paths Don’t hard code databases Don’t hard code properties Don’t do it in the tests either

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Profiles Very useful - but don’t abuse them Document them all Avoid depending on the environment

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Portable Artifacts

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value="org.hsqldb.jdbcDriver" value="jdbc:hsqldb:database"

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Portable Artifacts Artifacts in repository must be unique Either by classifier, or being portable Recommend externalising configuration database target environment properties 32

Resource Filtering

${ } Use with great care!

Centralisation, not substitution

✓ google.analytics.code=UA-1234567-1 X database.password=reallysecretpword

Useful for once-off alterations

Consider externalising configuration

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Shared Resources Don’t duplicate resources across projects ZIP and put in the repository Use the dependency plugin to retrieve

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Reproducibility Ensuring Reproducible Builds 35

Reproducibility Important for releases More important for source releases Build must be isolated from change Portability is a pre-requisite

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The Enforcer org.apache.maven.plugins maven-enforcer-plugin 1.0-alpha-4 enforce true true ... 37

The Enforcer org.apache.maven.plugins maven-enforcer-plugin 1.0-alpha-4 enforce true true ...

true true

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The Enforcer Help ensure build will be reproducible Based on rules force specific plugin versions ban snapshots global exclusions force Maven/Java/OS version can write your own 39

Releasing Release Early, Often and Right 40

Releases Set the project version to a -SNAPSHOT Make them early and often Use Maven tools to automate

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Questions? Brett Porter - [email protected] Better Builds with Maven, blog at http://www.devzuz.org/