Introduction tomaven
- 1. Introduction to MavenIntroduction to Maven
- 2. Notes • This is a training NOT a presentation • Please ask questions • Prerequisites – Introduction to the Java Stack – Basic Java and XML skillz
- 3. • Introduce Maven • Basic Maven Pom File and Project Structure • Dependencies
- 4. Maven Background • Is a Java build tool – “project management and comprehension tool” • An Apache Project – Mostly sponsored by Sonatype • History – Maven 1 (2003) • Very Ugly • Used in Stack 1 – Maven 2 (2005) • Complete rewrite • Not backwards Compatible • Used in Stack 2.0,2.1,2.2,3.0 – Maven 3 (2010) • Same as Maven 2 but more stable • Used in Stack 2.3, 3.1
- 5. Maven Features • Dependency System • Multi-module builds • Consistent project structure • Consistent build model • Plugin oriented • Project generated sites
- 6. The Maven Mindset • All build systems are essentially the same: – Compile Source code – Copy Resource – Compile and Run Tests – Package Project – Deploy Project – Cleanup • Describe the project and configure the build – You don’t script a build – Maven has no concept of a condition – Plugins are configured
- 7. Other Java Build Tools • Ant (2000) – Granddaddy of Java Build Tools – Scripting in XML – Very flexible • Ant+Ivy (2004) – Ant but with Dependency Management • Gradle (2008) – Attempt to combine Maven structure with Groovy Scripting – Easily extensible – Immature
- 8. Maven Learning Resources • Maven Homepage – http://maven.apache.org • Reference Documentation for Maven • Reference Documentation for core Plugins • Sonatype Resources – http://www.sonatype.com/resource-center.html • Free Books • Videos
- 9. Maven POM • Stands for Project Object Model • Describes a project – Name and Version – Artifact Type – Source Code Locations – Dependencies – Plugins – Profiles (Alternate build configurations) • Uses XML by Default – Not the way Ant uses XML
- 10. Project Name (GAV) • Maven uniquely identifies a project using: – groupID: Arbitrary project grouping identifier (no spaces or colons) • Usually loosely based on Java package – artfiactId: Arbitrary name of project (no spaces or colons) – version: Version of project • Format {Major}.{Minor}.{Maintanence} • Add ‘-SNAPSHOT ‘ to identify in development • GAV Syntax: groupId:artifactId:version <?xml version="1.0" encoding="UTF-8"?> <project> <modelVersion>4.0.0</modelVersion> <groupId>org.lds.training</groupId> <artifactId>maven-training</artifactId> <version>1.0</version> </project>
- 11. Packaging • Build type identified using the “packaging” element • Tells Maven how to build the project • Example packaging types: – pom, jar, war, ear, custom – Default is jar <?xml version="1.0" encoding="UTF-8"?> <project> <modelVersion>4.0.0</modelVersion> <artifactId>maven-training</artifactId> <groupId>org.lds.training</groupId> <version>1.0</version> <packaging>jar</packaging> </project>
- 12. Project Inheritance • Pom files can inherit configuration – groupId, version – Project Config – Dependencies – Plugin configuration – Etc. <?xml version="1.0" encoding="UTF-8"?> <project> <parent> <artifactId>maven-training-parent</artifactId> <groupId>org.lds.training</groupId> <version>1.0</version> </parent> <modelVersion>4.0.0</modelVersion> <artifactId>maven-training</artifactId> <packaging>jar</packaging> </project>
- 13. Multi Module Projects • Maven has 1st class multi-module support • Each maven project creates 1 primary artifact • A parent pom is used to group modules <project> ... <packaging>pom</packaging> <modules> <module>maven-training</module> <module>maven-training-web</module> </modules> </project>
- 14. Maven Conventions • Maven is opinionated about project structure • target: Default work directory • src: All project source files go in this directory • src/main: All sources that go into primary artifact • src/test: All sources contributing to testing project • src/main/java: All java source files • src/main/webapp: All web source files • src/main/resources: All non compiled source files • src/test/java: All java test source files • src/test/resources: All non compiled test source files
- 15. Maven Build Lifecycle • A Maven build follow a lifecycle • Default lifecycle – generate-sources/generate-resources – compile – test – package – integration-test (pre and post) – Install – deploy • There is also a Clean lifecycle
- 16. Example Maven Goals • To invoke a Maven build you set a lifecycle “goal” • mvn install – Invokes generate* and compile, test, package, integration-test, install • mvn clean – Invokes just clean • mvn clean compile – Clean old builds and execute generate*, compile • mvn compile install – Invokes generate*, compile, test, integration-test, package, install • mvn test clean – Invokes generate*, compile, test then cleans
- 17. Maven and Dependencies • Maven revolutionized Java dependency management – No more checking libraries into version control • Introduced the Maven Repository concept – Established Maven Central • Created a module metadata file (POM) • Introduced concept of transitive dependency • Often include source and javadoc artifacts
- 18. Adding a Dependency • Dependencies consist of: – GAV – Scope: compile, test, provided (default=compile) – Type: jar, pom, war, ear, zip (default=jar) <project> ... <dependencies> <dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>2.5</version> <scope>provided</scope> </dependency> </dependencies> </project>
- 19. Maven Repositories • Dependencies are downloaded from repositories – Via http • Downloaded dependencies are cached in a local repository – Usually found in ${user.home}/.m2/repository • Repository follows a simple directory structure – {groupId}/{artifactId}/{version}/{artifactId}-{version}.jar – groupId ‘.’ is replaced with ‘/’ • Maven Central is primary community repo – http://repo1.maven.org/maven2
- 20. Proxy Repositories • Proxy Repositories are useful: – Organizationally cache artifacts – Allow organization some control over dependencies – Combines repositories • ICS uses the Nexus repository manager • All artifacts in Nexus go through approval process – License verified – Improve organizational reuse • To request approval create issue in SDS jira project: – https://jira.ldschurch.org/jira/browse/SDS
- 21. Defining a repository • Repositories are defined in the pom • Repositories can be inherited from parent • Repositories are keyed by id • Downloading snapshots can be controlled <project> ... <repositories> <repository> <id>lds-main</id> <name>LDS Main Repo</name> <url>http://code.lds.org/nexus/content/groups/main-repo</url> <snapshots> <enabled>false</enabled> </snapshots> </repository> </repositories> </project>
- 22. Transitive Dependencies • Transitive Dependency Definition: – A dependency that should be included when declaring project itself is a dependency • ProjectA depends on ProjectB • If ProjectC depends on ProjectA then ProjectB is automatically included • Only compile and runtime scopes are transitive • Transitive dependencies are controlled using: – Exclusions – Optional declarations
- 23. Dependency Exclusions • Exclusions exclude transitive dependencies • Dependency consumer solution <project> ... <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>3.0.5.RELEASE</version> <exclusions> <exclusion> <groupId>commons-logging</groupId> <artifactId>commons-logging</artifactId> </exclusion> </exclusions> </dependency> </dependencies> </project>
- 24. Optional Dependencies • Don’t propagate dependency transitively • Dependency producer solution • Optional is under used <project> ... <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>3.0.5.RELEASE</version> <optional>true</optional> </dependency> </dependencies> </project>
- 25. Dependency Management • What do you do when versions collide? – Allow Maven to manage it? • Complex and less predictable – Take control yourself • Manage the version manually • In Java you cannot use both versions <project> ... <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>3.0.5.RELEASE</version> </dependency> </dependencies> </dependencyManagement> </project>
- 26. Using Dependency Management • Other uses for Dependency Management – Allowing parent pom to manage versions – Unify exclusions <project> ... <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>3.0.5.RELEASE</version> </dependency> </dependencies> </dependencyManagement> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> </dependency> <!-- Look ma, no version! --> </dependencies> </project>
- 27. Summary • Maven is a different kind of build tool • It is easy to create multi-module builds • Dependencies are awesome
Editor's Notes
- #3: A few disclaimers to get things started