PracticesBest

${artifactId}

${pom.artifactId}${project.artifactId}

${project.build.sourceDirectory}

vs

<project> <groupId>my.group</groupId> <artifactId>parent</artifactId> <version>1.0.0</version> <properties> <baseId>cool-project</baseId> </properties></project>

<project> <parent> <groupId>my.group</groupId> <artifactId>parent</artifactId> <version>1.0.0</version> </parent> <artifactId>${baseId}-extra</artifactId></project>

<project> <groupId>my.group</groupId> <artifactId>parent</artifactId> <version>1.0.0</version> <properties> <baseId>cool-project</baseId> <globalVersion>4.3.2</globalVersion> </properties></project>

<project> <parent> <groupId>my.group</groupId> <artifactId>parent</artifactId> <version>1.0.0</version> </parent> <artifactId>${baseId}-extra</artifactId> <properties> <baseId>cool-project</baseId> <globalVersion>9.2.1</globalVersion> </properties></project>

parent

application

module

knows of extends of

/project/pom.xml

/project/parent/pom.xml

/project/module1/pom.xml/project/module2/pom.xml

3typesofPOMs

parent

application

module

knows of extends of

/project/pom.xml

/project/parent/pom.xml

/project/module1/pom.xml/project/module2/pom.xml

3typesofPOMs

parentPOM

sho

uld know

nothingabout

the applicationmodulesand its

<project> <groupId>my.group</groupId> <artifactId>parent</artifactId> <version>1.0.0</version> <packaging>pom</packaging>

<build> <pluginManagement/> </build> <ciManagement/> <contributors/> <developers/> <dependencyManagement/> <distributionManagement/> <inceptionYear/> <issueManagement/> <licenses/> <mailingLists/> <name/> <organization/> <prerequisites/> <properties/> <scm/> <url/></project>

parent POM

definesenvironmentfor

modulePOMs

<project> <groupId>my.group</groupId> <artifactId>parent</artifactId> <version>1.0.0</version> <packaging>pom</packaging>

<build> <pluginManagement/> </build> <ciManagement/> <contributors/> <developers/> <dependencyManagement/> <distributionManagement/> <inceptionYear/> <issueManagement/> <licenses/> <mailingLists/> <name/> <organization/> <prerequisites/> <properties/> <scm/> <url/></project>

parent POM

definesenvironmentfor

modulePOMs

<project> ... <dependencyManagement> <dependencies> <dependency> <!-- Required --> <groupId>my.depend</groupId> <artifactId>application-api</artifactId> <version>${depend.version}</version>

<!-- Only when non-default --> <classifier></classifier> <type></type>

<!-- Don't do it --> <exclusions/> <optional/> <scope/> </dependency> </dependencies> </dependencyManagement> ...</project>

parentPOM

<project> ... <build> <pluginManagement> <plugins> <plugin> <!-- Required --> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-deploy-plugin</artifactId> <version>2.7</version>

<!-- Don't do it --> <configuration/> <dependencies/> <executions/> <extensions/> <goals/> <inherited/> </plugin> </plugins> </pluginManagement> </build> ...</project>

parentPOM

<project> <parent> <groupId>my.group</groupId> <artifactId>parent</artifactId> <version>1.0.0</version> <relativePath>../parent/pom.xml</relativePath> <parent> <artifactId>module1</artifactId> <packaging>jar</packaging>

<dependencies/> <build> <plugins/> </build>

<contributors/> <developers/> <name/>

<!-- Avoid when possible --> <profiles/></project>

modulePOM

<project> <parent/> <artifactId>module1</artifactId> <packaging>jar</packaging>

<dependencies> <dependency> <groupId>my.depend</groupId> <artifactId>application-api</artifactId> <!-- Don't do it --> <version>${depend.version}</version> </dependency> </dependencies>

<build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-deploy-plugin</artifactId> <!-- Don't do it --> <version>2.7</version> </plugin> </plugins> </build> ...</project>

modulePOM

applicationPOM

<project> <groupId>my.group</groupId> <artifactId>application</artifactId> <version>1.0.0</version> <packaging>pom</packaging> <modules> <module>parent</module> <module>module1</module> </modules>

<build> <plugins/> </build>

<contributors/> <developers/> <distributionManagement/> <name/> <profiles/> <scm/>

<!-- Don't do it --> <dependencies/></project>

applicationPOM

shouldworkwithout

specifingany

profile! $ mvn clean verify…[INFO] BUILD SUCCESS

Make

use

DO NOT

buildsdependable

versioned artifactsSNAPSHOT

OT

one artifactto rule all

DO NOT

OTcreate

specific artifactsenvironment

environments

environment specifics is configuration!

clean POM

==clean & smaller

artifacts

faster builds==

mvn help:effective-pommvn dependency:analyze

Summary (1)

1. Don't use deprecated references

2. Try to avoid using inherited properties

3. Variables in POM files are processed after inheritance

4. Set dependencyManagement in the parent POM to define all dependency versions without scope

5. Use properties to define the dependency versions

6. Do not use SNAPSHOT versioned artifacts

Summary (2)

7. Do not create environment specific artifacts

8. Set pluginManagement in the parent POM to define versions for all plugins (incl. standard Maven plugins)

9. Use the relativePath tag to point to parent pom.xml

10. Keep POMs clean (use mvn help:effective-pom and mvn dependency:analyze)

11. distributionManagement and scm configuration in the POM, repositories and pluginRepositories in Maven settings.xml

12. Build must pass when no profile has been activated