Apache Maven

https://maven.apache.org/

https://maven.apache.org/what-is-maven.html

• POM = Project Object Model
• POM + Plugins
• Maven suggest guidelines for project directory layout

• Features of Maven
  • simple project setup
  • using across many projects
    • ⇒ no ramp-up time for new developers
  • dependency management
  • repository of libs and metadata
  • model-based builds
    • JAR, WAR, …
  • release management and distribution publication
    • For example:
      • integration with SCMs (e.g. Git)
      • releases based on a tag
      • source ditribution

https://maven.apache.org/guides/getting-started/maven-in-five-minutes.html

mvn archetype:generate -DgroupId=com.mycompany.app -DartifactId=my-app -DarchetypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.4 -DinteractiveMode=false

• archetype:generate
  • archetype - plugin
  • generate - goal
• A plugin can be understood as a “collection” of goals.
• this generate call has created a standard directory layout. Like:
  • my-app
    • pom.xml
    • /src
      • /main
        • /java
          • …
        • …
      • /test
        • /java
          • …
        • …

• Build the project:
  • mvn package
    • package is a phase (not a goal as archetype:generate)
    • When a phase is given, Maven executes every phase in the sequence up to and including the one defined.
• To use proper Java version, maven-compiler-plugin should be properly configured, because by default it uses Java 8.
• Default Maven build lifecycle:
  • validate: validate the project is correct and all necessary information is available
  • compile: compile the source code of the project
  • test: test the compiled source code using a suitable unit testing framework. These tests should not require the code be packaged or deployed
  • package: take the compiled code and package it in its distributable format, such as a JAR.
  • integration-test: process and deploy the package if necessary into an environment where integration tests can be run
  • verify: run any checks to verify the package is valid and meets quality criteria
  • install: install the package into the local repository, for use as a dependency in other projects locally
  • deploy: done in an integration or release environment, copies the final package to the remote repository for sharing with other developers and projects.
• Other build lifecycles (not in default):
  • clean: cleans up artifacts created by prior builds
  • site: generates site documentation for this project
• Phases are actually mapped to underlying goals. The specific goals executed per phase is dependant upon the packaging type of the project. For example, package executes jar:jar if the project type is a JAR, and war:war if the project type is a WAR.
• An interesting thing to note is that phases and goals may be executed in sequence:
  • mvn clean dependency:copy-dependencies package

https://maven.apache.org/guides/getting-started/index.html

• Maven helps to manage:
  • builds
  • documentation
  • reporting
  • dependencies
  • SCMs
  • releases
  • distribution
• How to make a first Maven project?
  • archetypes = “templates” of a project
  • mvn archetype:generate
    • Example:
      • mvn -B archetype:generate -DgroupId=my.company.app DartifactId=my-app -DarchetypeVersion=1.4 -DarchetypeArtifactId=maven-archetype-quickstart
  • pom.xml
    • contains Project Object Model
  • artifactId
    • used for the names of project artifacts
      • e.g. primary artifact (typically JAR): myapp-1.0.jar
  • properties
    • value placeholders accessible anywhere within a POM
• How do I compile my application sources?
  • mvn compile
  • mvn test
    • compile + execute unit tests
  • mvn test-compile
    • compile unit tests (without executing)
• How do I create a JAR and install it in my local repository?
  • mvn package
    • packages JAR in “target” directory
  • mvn install
    • installs the JAR in the local repo (default: ${user.home}/.m2/repository)
• How do I use plugins?
  • configuration element applies the given parameters to every goal from the plugin
• How do I add resources to my JAR?
  • use standard directory layout
    • /src/main/resources
      • → goes to the root of JAR
    • /src/test/resources
      • can be addressed in Java code for example as:
        • InputStream in = getClass().getResourceAsStream(“/test.properties”);
• How do I filter resource files?
  • To reference a property which value will be known firstly at the build time use ${<property_name>}
  • The value of such property can be defined in:
    • pom.xml
      • ${<property_name>}
        • e.g. ${project.name}
    • settings.xml
      • ${settings.<property_name>}
        • e.g.${settings.localRepository}
    • external properties file
    • system property
• How do I use external dependencies?
  • dependencies section in pom.xml lists all external dependencies
  • each dependency entry defines at least:
    • groupId
    • artifactId
    • version
    • scope
      • e.g. test or compile
  • dependencies will be fetched from local repo (default: ${user.home}/.m2/repository)
    • with command: mvn install
  • if dependency is not in local repo, it will be fetched from a remote repo (by default Maven Central: https://repo.maven.apache.org/maven2)
• How do I deploy my JAR in my remote repository?
  • configure repo URL in the pom.xml
  • authentication info in settings.xml
• How do I build more than one project at once?
  • …

. . .

https://maven.apache.org/guides/introduction/introduction-to-the-lifecycle.html

Three built-in build lifecycles:

• default
  • The default lifecycle handles your project deployment
• clean
  • the clean lifecycle handles project cleaning
• site
  • the site lifecycle handles the creation of your project's web site.

The full Lifecycle reference.

Default lifecycle:

• validate - validate the project is correct and all necessary information is available
• compile - compile the source code of the project
• test - test the compiled source code using a suitable unit testing framework. These tests should not require the code be packaged or deployed
• package - take the compiled code and package it in its distributable format, such as a JAR.
• verify - run any checks on results of integration tests to ensure quality criteria are met
• install - install the package into the local repository, for use as a dependency in other projects locally
• deploy - done in the build environment, copies the final package to the remote repository for sharing with other developers and projects.

• Maven Release Plugin
  • Maven Release Plugin - Usage

• Introduction to the POM