Apache Maven: J2EE Front to Back

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Apache MavenJ2EE Front to Back

• Jesse McConnell - jmcconnell_at_apache.org

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J2EE Application Development by Convention

• No laughing matter
• People cry everyday because of j2ee
• Maven can help keep crying to a minimum
• hopefully

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Who Am I?

• On Maven PMC
• Active in Continuum
• Some maven plugins
• Some mojo plugins _at_ codehaus
• Axistools-maven-plugin - dont hold that against
  mepls
• Redback _at_ codehaus

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Components of J2ee

• EJBs
• Maven-ejb-plugin
• Web Services
• Axistools-maven-plugin
• Xfire-maven-plugin
• others
• Web Archives (Wars)
• Maven-war-plugin
• Enterprise Archives (Ears)
• Maven-ear-plugin

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Maven Lifecycle

• Supported since the beginning with maven 2
• J2EE artifact lifecycle is managed through
  dependencies
• Artifact construction dictated by lttype/gt

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Understanding Structure in Maven

• Follow Conventions
• Archiva and Continuum are good example Web
  Applications
• Redback is security overlay packaged as a Web
  Application and overlaid

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Library Code

• Understanding the final goal and scoping
  dependencies appropriately.
• That meansunderstand J2EE classloaders
• Understand your Container
• Like to think they are all interchangeable
• Can be harder in practice

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EJB Structure and Management

• ltpackaginggtejblt/packaginggt
• Directory Layout
• -- pom.xml
• -- src
• -- main
• -- resources
• -- META-INF
• -- ejb-jar.xml

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EJB Structure and Management

• Plugin Example
• ltplugingt
• ltartifactIdgtmaven-ejb-pluginlt/artifactIdgt
• ltconfigurationgt
• ltgenerateClientgttruelt/generateClientgt
• lt/configurationgt
• lt/plugingt

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Linking into Build

• Validates ejb-jar.xml file existence
• Unless you specify ejbVersion 3.0

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Testing EJB Code

• Best bet is testing modularly like with normal
  junit testing.

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Web Service Structures and Management

• No strict lifecycle phase
• No strict directory layout
• Depends on web service architecture in use
• Xfire -gt CXF, Axis, etc

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Linking into Build

• Consider services, clients, resource libraries
• Common project layout
• Annotations of services
• All kinda implementation specific
• Real deal is testing them

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Testing Web Services

• Can be hard to test directly
• Client testing against established servers begs
  irreproducibility
• Test by deploying services to embedded jetty and
  running client code

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War Structure and Management

• ltpackaginggtwarlt/packaginggt
• Directory Layout
• -- pom.xml
• -- src
• -- main
• -- java
• -- com
• -- example
• -- projects
• -- SampleAction.java
• -- resources
• -- images
• -- sampleimage.jpg
• -- sampleresource
• -- webapp
• -- WEB-INF
• -- web.xml
• -- index.jsp
• -- jsp

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War Structure and Management

• Plugin Example
• ltplugingt
• ltgroupIdgtorg.apache.maven.pluginslt/groupId
  gt
• ltartifactIdgtmaven-war-pluginlt/artifactIdgt
• ltversiongt2.0lt/versiongt
• ltconfigurationgt
• ltwebappDirectorygt/sample/servlet/contai
  ner/deploy/directorylt/webappDirectorygt
• lt/configurationgt
• lt/plugingt

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War Overlay

• Often handy to build component oriented wars.
• Overlay multiple war files to create actual war
  file.
• Continuum and Archiva do this is redback for
  common security and user management

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Linking into Build

• Dependency management scoping is key
• Dig into your war file and see what is in there
• ltscopegtprovidedlt/scopegt can be your friend

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Three different usages

• Warwar - standard war creation
• Warexploded - builds out war in exploded format
  in target dir
• Warinplace - builds out webapp in
  src/main/webapp
• Dependency Management scoping key for war
  usability

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Testing Wars

• Deploy via Jetty-maven-plugin during development
• Selenium-maven-plugin for automated testing

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Scoping War Dependencies

• Two Approaches, different scoping
• Deploying Wars
• Integrating into Ears

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Ear Structure and Management

• Directory Layout
• No specific directories required
• Dependencies are key to ear files
• Automatic application.xml creation
• MANIFEST.MF Creation

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Ear Structure and Management

• Plugin Example
• ltplugingt
• ltartifactIdgtmaven-ear-pluginlt/artifact
  Idgt
• ltconfigurationgt
• ltarchivegt
• ltmanifestgt
• ltaddClasspathgttruelt/addClassp
  athgt
• lt/manifestgt
• lt/archivegt
• lt/configurationgt
• lt/plugingt

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Linking into Build

• Just do it
• Then triage.
• Primary recommendation, keep your project modular
• Test your modules
• Use ear module as simply the aggregation of the
  project
• packaging

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Testing Ears

• No easy peasy way
• Have to deploy somewhere
• Have to start something
• Have to access it
• Non-trivial task
• Best off testing your stuff modularly before you
  get to this point.

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Scoping Ear Dependencies

• Learn Dependency Management in parent poms
• Love it
• Plan for ear deployement, scope things that are
  used by multiple war and ejbs as provided or
  test in those poms
• Scope for inclusion in ear, leave versioning to
  the dependencyManagement, its why it is there

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Application Deployment Options

• Cargo-maven-plugin
• Largely area untargeted by maven conventions
• Hard to standardize in real world

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Tips and Tricks

• 300M Ear file
• Check the Scoping
• Pull apart the artifacts and look for jar
  duplication
• Understand those classloaders

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Using Archetypes

• Example of Quick Project Startup

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Questions?

• Jesse McConnell - jmcconnell_at_apache.org
• Better Builds with Maven, blog at
  http//www.devzuz.org