1. Basic Maven Chris Roeder Kevin Livingston April 2011 5/5/11 1 Chris Roeder, Kevin Livingston

2. Maven Big Picture: Builds: Maven will compile your code and assemble jars. (similar to ant’s function) Dependency Management: Maven will fetch other jars your project uses and assemble a CLASSPATH for the compiler. (similar to ivy’s function) Integrate with Eclipse: by way of plugins like m2. The goal of this talk is to get you started, not to make an expert of you. 5/5/11 Chris Roeder, Kevin Livingston 2

3. Contents Introduction Dependency Manangement Builds and pom files Modules Repositories Releases and Snapshots Mojo: Plugins, Goals, Phases Runtime Review, Advanced Topics, Caution Thanks 5/5/11 Chris Roeder, Kevin Livingston 3

4. Introduction 1 Dependency Manager:Given a description of dependent jars, Maven will fetch them for you Build Tool: Convention over ConfigurationIf your project follows a standard layout, things just work (with no ant files) Running: Maven will assemble as classpath for you at runtime. Consider what this means for deployment. 5/5/11 4 Chris Roeder, Kevin Livingston

5. Introduction 2 Maven is organized around projects that produce a single jar.(or sets of projects that each produce a jar) Each project has a pom.xml file, a “pom”, that configures it. The pom describes the project and its dependencies. Each with 3 “coordinates”: Group ID (edu.ucdenver.ccp) Artifact ID (common) Version (1.0) 5/5/11 5 Chris Roeder, Kevin Livingston

6. Introduction: Convention over Configuration A big Maven philosophy is that life is easier with clear conventions: You know what to expect The tool knows what to expect, so… …it can run with little configuration. Made popular by Ruby on Rails, and others. Conventions (defaults) are declared in a (mostly) invisible “super pom” 5/5/11 6 Chris Roeder, Kevin Livingston

7. Dependency Management Maven is declarative (not imperative): Specify the jars used, where they come from, and what release, and Maven will manage the files without explicit coding. Maven manages the files. You don’t need a “lib” directory …even in eclipse. No modifying the project’s classpath. 5/5/11 7 Chris Roeder, Kevin Livingston

8. Dependency Management: Adding a new jar Google “maven junit” to find the dependency for junit. Add this to your pom.xml (maven file): <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.8.2</version></dependency> Even if the jar filename has no version, Maven keeps track. Pom search engines include: http://mvnrepository.com/ 5/5/11 8 Chris Roeder, Kevin Livingston

9. Dependency Management:Finding the Jar Most jars are in “The” repository, a public central repository for community use. Sometimes the are not, so tell Maven about other repositories: <repository> <name>Clojure main release repository</name><id>clojure-releases</id> <url>http://build.clojure.org/releases</url> </repository> You can usually find this in the same place as the dependency you Googled. 5/5/11 9 Chris Roeder, Kevin Livingston

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12. Build Tool By default, Maven: knows where to find the code and resources. You told it where and what the dependent jars are. Convention tells it where the new jar should go and what it should be named. Runs the “install” goal, making a jar available to more maven process. (more about goals coming) 5/5/11 12 Chris Roeder, Kevin Livingston

13. Example POM <?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http//www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding></properties><modelVersion>4.0.0</modelVersion><groupId>edu.ucdenver.ccp</groupId><artifactId>common</artifactId><packaging>jar</packaging><version>1.0-SNAPSHOT</version> <name>${project.artifactId}</name> <description>ccp common code</description> 5/5/11 13 Chris Roeder, Kevin Livingston Project “Coordinates”

14. Example POM (cont) <project> …<dependencies> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.12</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.8.2</version> <scope>test</scope> </dependency> </dependencies></project> 5/5/11 14 Chris Roeder, Kevin Livingston

15. Example POM: Repository Stanza <repositories> <repository><id>apache incudbaor</id><name>apache-incubator</name><url>http://people.apache.org/repo/m2-incubating-repository/</url> </repository> <repository><id>cleartk-googlecode</id> <name>ClearTK Google Code repository</name> <url>http://cleartk.googlecode.com/svn/repo</url> <snapshots><enabled>true</enabled> </snapshots> </repository></repositories> 5/5/11 15 Chris Roeder, Kevin Livingston

16. Build Tool: unconventional If you must work in a directory structure that doesn’t follow the convention… …just tell it where to find things: <build> <sourceDirectory>src</sourceDirectory> <resources> <resource> <directory>resources</directory> </resource> </resources></build> Maven rhetoric “highly discourages” this, but it doesn’t seem to be an issue. 5/5/11 16 Chris Roeder, Kevin Livingston

17. Modules:Families of Projects You can have a “super project” that binds a number of sub-projects together. A directory and a pom. The directory can sit besides the others. The pom goes in it.<?xml version="1.0" encoding="UTF-8"?><project> <modelVersion>4.0.0</modelVersion> <groupId>SciKnowMine</groupId> <artifactId>SciKnowMine</artifactId> <version>0.0.2-SNAPSHOT</version> <packaging>pom</packaging> <modules> <module>../SciKnowMineCore</module> <module>../SciKnowMineCitationStore</module> <module>../SciKnowMineTriage</module> <module>../SciKnowMinePreProcessing</module> </modules></project> Allows you to run them all from this one directory. 5/5/11 17 Chris Roeder, Kevin Livingston

18. Parent Pom A parent pom may be declared for each module that specifies common resources, dependencies, properties, etc. The parent looks normal. Children declare it as a parent: <parent> <groupId>edu.ucdenver.ccp</groupId> <artifactId>kr</artifactId> <version>1.0-SNAPSHOT</version></parent> Can be combined with main module from previous slide. 5/5/11 Chris Roeder, Kevin Livingston 18

19. Properties Not called “variable” because they aren’t Declare them: <properties> <clojure.version>1.2.0</clojure.version> <ver.jena>2.6.3</ver.jena> <ver.arq>2.8.5</ver.arq> <ver.sesame>2.3.2</ver.sesame></properties> Use them: <dependency> <groupId>org.clojure</groupId> <artifactId>clojure</artifactId> <version>${clojure.version}</version></dependency> 5/5/11 Chris Roeder, Kevin Livingston 19

20. Repositories Maven uses three levels of repositories: Reactor: not really a repository. It’s part of a particular run. Install: your personal repository: ~/.m2/repository Deploy: something like a web server of jars They are used sequentially: if an artifact (jar) is not available in the Reactor, it looks in your ~/.m2. If not there, it searches for deployments in repositories. Really, there are two kinds of Deployment repositories: You company’s local, private one, that caches. Globally available repositories where things are publicly available. The local repository also hosts “in-house” code. 5/5/11 20 Chris Roeder, Kevin Livingston

21. Artifactory Artifactory is the Maven repository implementation used here: http://amc-bakeoff.ucdenver.pvt:8081 It’s used to cache artifacts (jars) from other repositories to reduce network load and load on those community repositories. It also hosts locally developed artifacts. 5/5/11 21 Chris Roeder, Kevin Livingston

22. Snapshots Maven doesn’t deal strictly with perfectly prepared releases. Snapshots are a way of sharing a work-in-progress. If you specify a dependency as a snapshot, you get the latest and greatest: the most recently published. The Maven repositories deal with keeping track of them and which is the most recent. You can fix on a particular snapshot by referring to it using it’s timestamp. 5/5/11 22 Chris Roeder, Kevin Livingston

23. Snapshots 2 A snapshot’s version says “SNAPSHOT”: <version>0.0.2-SNAPSHOT</version> A repository has to be marked as one that holds snapshots: <repository> <id>clojure-snapshots</id> <url>http://build.clojure.org/snapshots</url> <snapshots><enabled>true</enabled> </snapshots> </repository> Dependencies too: <dependency> <groupId>swank-clojure</groupId> <artifactId>swank-clojure</artifactId><version>1.3.0-SNAPSHOT</version></dependency> 5/5/11 Chris Roeder, Kevin Livingston 23

24. Plugins Maven uses plugins to add functionality. They are retreived like other artifacts: from repositories. They are configured in stanzas called “plugin” Their commands start with the plugin name: Exec:java, for example is the exec plugin’s java goal Plugin goals are called “Mojo” in Maven 5/5/11 24 Chris Roeder, Kevin Livingston

25. Example Plugin Stanza <plugin><groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>2.0.2</version> <configuration><source>1.6</source><target>1.6</target> </configuration></plugin> 5/5/11 25 Chris Roeder, Kevin Livingston

26. Mojo:Maven CommandsGoals Maven is implemented in a number of plugins. Each plugin has one or more goals (commands) giving your install some kind of “mojo” Goals are executed by naming them and their plugin: <plugin>:<goal> mvnarchetype:generate Maven groups goals can be associated with “lifecycle phases”, and run simply by naming a phase mvninstall 5/5/11 26 Chris Roeder, Kevin Livingston

27. Maven Phases A phase can have zero or more goals associated with it. A lifecycle is a series of phases leading up to a package type. Phases are ordered, and require successful completion of prior phases. The default lifecycle is for jars, and consists of phases that run the following goals: 5/5/11 Chris Roeder, Kevin Livingston 27

28. Runtime Tool A plugin, exec, allows you to call java from Maven so you can use the classpath assembly features to run. Consider what possibilities this creates: Deliver a running project with just one file: the pom. 5/5/11 28 Chris Roeder, Kevin Livingston

29. Runtime 2: The getResourceAsStream Soap Box Not all projects remain naïve of the file system. Some expect to be able to open files using either absolute or relative filepaths and the File class. These files can’t be buried in a jar file. Use maven-assembly-pack to build a deployment assemply. Unpack with maven-dependency-unpack. 5/5/11 Chris Roeder, Kevin Livingston 29

30. Review: Maven Vocabulary Project Pom – a file that tells maven about a particular project. Artifact – a jar, war, pom or other thing required by a project Dependency – something your project needs from another project. Coordinates – the comination of attributes that identify an artifact Repository – a place for artifacts. Lifecycle – a series of steps to produce an artifact. Phase – one of the steps in a Lifecycle. Plugin (Mojo) – added capability Install – putting an artifact into your local ~/.m2/repository Deploy – putting an artifact into a repository Reactor – a process that analyzes and resolves dependencies and runs the build. It is the innermost (if temporary) container of artifacts. 5/5/11 Chris Roeder, Kevin Livingston 30

31. Review: Standard Directory Layout (with UIMA additions) http://maven.apache.org/guides/introduction/introduction-to-the-standard-directory-layout.html src main Java edu.isi.bmkeg… Resources desc/ae desc/cpe desc/cr typeSystem models test java resources target Product-0.1-SNAPSHOT.jar (created by build run) 5/5/11 Chris Roeder, Kevin Livingston 31

32. Advanced Topics(not covered here) Archetypes are a way of building a template for maven templates (poms). Maven does a lot in terms of Dependency Management: What if you have 2 jars that each depend on a third jar, but different versions? Maven picks the most recent, but this assumes backward compatibility. Scope: items within maven can be scoped to a phase, so for example, jUnit doesn’t have to ship with the production jar. SCM integration: How does this integrate with Subversion? Eclipse Integration: m2 eclipse plugin Site Utilities: a project info web site can be built that includes author and test info. among others. 5/5/11 Chris Roeder, Kevin Livingston 32

33. Caution The learning curve can be steep. Be patient: you’ll write less SCM code. Follow Convention. Don’t be afraid to violate Convention. Get a second opinion. Read the errors bottom-up. Run “mvn clean” and “rm ~/.m2/repository” when things get real weird. http://www.sonatype.com/books/mvnex-book/reference/public-book.html 5/5/11 33 Chris Roeder, Kevin Livingston

34. Thank You Hunter Lab Software Engineers for keeping the bar high: Bill Baumgartner Yuriy Malenkiy ISI’s SciKnowMine project for using tools that practically require Maven: Cartic Ramakrishnan Gully Burns 5/5/11 34 Chris Roeder, Kevin Livingston