Contents
Overview
* POM: project object model
* POM is an xml file
* Used to build a project
Project Inheritance
* Following elements in POM are merged:
– dependencies
– developers and contributors
– plugin lists (including reports)
– plugin executions with matching ids
– plugin configuration
– resources
Super POM
* All POMs extends the super POM
* Default package: jar
* Default repository is central repository: https://repo1.maven.org/maven2/
Minimal POM
* Mandatory elements:
<project> <modelVersion>4.0.0</modelVersion> <groupId>com.mycompany.app</groupId> <artifactId>my-app</artifactId> <version>1</version> </project>
* Other elements inherit from super POM
Parent POM
* Specify parent pom:
<project> <modelVersion>4.0.0</modelVersion> <!-- can be omitted if same as parent --> <groupId>com.mycompany.app</groupId> <version>1</version> <!-- end --> <parent> <groupId>com.mycompany.app</groupId> <artifactId>my-app</artifactId> <version>1</version> <!-- if parent pom not in the dir one level above <relativePath>../parent/pom.xml</relativePath> --> </parent> <artifactId>my-module</artifactId> </project>
Project Aggregation
* Set packaging to: pom
* Specify child POMs as modules:
<project> <modelVersion>4.0.0</modelVersion> <groupId>com.mycompany.app</groupId> <artifactId>my-app</artifactId> <version>1</version> <packaging>pom</packaging> <modules> <module>my-module</module> </modules> </project>
Parent POM with Aggregation
* You can specify parent pom to also include modules:
<project> <modelVersion>4.0.0</modelVersion> <groupId>com.mycompany.app</groupId> <artifactId>my-app</artifactId> <version>1</version> <packaging>pom</packaging> <modules> <module>my-module</module> </modules> </project>
* Child POM:
<project> <modelVersion>4.0.0</modelVersion> <parent> <groupId>com.mycompany.app</groupId> <artifactId>my-app</artifactId> <version>1</version> <relativePath>pom.xml</relativePath> </parent> <artifactId>my-module</artifactId> </project>
Project Model Variables
* Variable values defined in child POM take precedence over parent values
* Project model variables
– any single value element can be referenced as a variable, e.g.:
${project.groupId}
${project.version}
${project.build.sourceDirectory}
${project.basedir}
${project.baseUri}
${maven.build.timestamp}Project Properties
* Any properties defined in project can be referenced as a variable:
<properties> <maven.build.timestamp.format>yyyy-MM-dd'T'HH:mm:ss'Z'</maven.build.timestamp.format> </properties>