Section 1.4. Compiling and Testing a Project | Maven: A Developers Notebook (Developers Notebooks)

1.4. Compiling and Testing a Project

You have a new project with one class and a unit test. Next, let's build the project and run the App class.

1.4.1. How do I do that?

Create a JAR file containing this application's classes by executing the jar:jar goal. The JAR plug-in defines a shorthand goal named jar which depends upon the jar:jar goal. Executing either goal will have the same result. All plug-ins define such a shortcut; for example, the test goal executes the test:test goal from the Test plug-in. Execute the jar goal with maven jar:

C:\dev\mavenbook\code\genapp\test-application>maven jar  _ _  _ _ |  \/  |_ _ _Apache_ _ _ _ _ | |\/| / _` \ V / -_) ' \  ~ intelligent projects ~ |_|  |_\_ _,_|\_/\_ _ _|_||_|  v. 1.0.2    Attempting to download junit-3.8.1.jar. 118K downloaded    build:start:    java:prepare-filesystem:     [mkdir] Created dir: C:\dev\mavenbook\code\genapp\test-application\target\classes    java:compile:     [echo] Compiling to C:\dev\mavenbook\code\genapp\test-application/target/classes     [echo]     [javac] Compiling 1 source file to C:\dev\mavenbook\code\genapp\test-application\ target\classes    java:jar-resources: Copying 1 file to C:\dev\mavenbook\code\genapp\test-application\target\classes    test:prepare-filesystem:     [mkdir] Created dir: C:\dev\mavenbook\code\genapp\test-application\target\ test-classes     [mkdir] Created dir: C:\dev\mavenbook\code\genapp\test-application\target\ test-reports    test:test-resources:    test:compile:     [javac] Compiling 3 source files to C:\dev\mavenbook\code\genapp\test-application\ target\test-classes    test:test:     [junit] Running mdn.testapp.AppTest     [junit] Tests run: 1, Failures: 0, Errors: 0, Time elapsed: 0.078 sec    jar:jar:     [jar] Building jar: C:\dev\mavenbook\code\genapp\test-application\target\ test-application-1.0.jar BUILD SUCCESSFUL Total time: 9 seconds

Maven creates a target directory to hold intermediate files and JAR files. Once the JAR has been created, execute the App class as follows:

Note: What's with the ^ and More? prompt? This is how a DOS command line is continued.

C:\dev\mavenbook\code\genapp\test-application> java ^  More? target\test-application-1.0.jar mdn.testapp.App Hello World!

If you want to do this again, run maven clean to remove the target directory and build from scratch.

Note: Maven just works. The first time it needs to run unit tests it is smart enough to download JUnit for you if you don't have it locally. No more searching for JAR files on the Web.

1.4.2. What just happened?

When you ran the jar goal, Maven used the JAR plug-in to create a JAR artifact. First, Maven figured out that it had to run a series of goals to be able to create this application's JAR file; the JAR plug-in has a jar:jar goal which depends on other goals which, in turn, depend on other goals. Maven figured out that the following sequence of goals needed to be executed: java:prepare-filesystem, java:compile, java:jar-resources, test:prepare-filesystem, test:test-resources, test:compile, and test:test.

Maven saw that it needed to execute a goal from the Test plug-in which executes JUnit tests, and it checked the local Maven repository for the JUnit JAR file. Because you haven't used Maven yet, it downloaded junit-3.8.1.jar from Maven's default repository at http://www.ibiblio.org/maven/. You'll learn about the local Maven repository and Maven's powerful dependency management capabilities later in this chapter.