Packaging A Robot To A Jar from the Command Line?

Maven has a declarative approach to build scripts, in contrast to Ant which has an imperative approach.

Since most build scripts all end up doing the same thing, like deleting files from a previous build (clean), compiling source (compile) a packaging compiled files (package), Maven standardized these steps in a hard-coded life-cycle. Also, Maven has a programming-by-exception approach, with defaults for all configurations. What you basically do in Maven is reconfigure what you want different from the basic life-cycle, and Maven does the rest.

If you execute an "empty" Maven script with "mvn clean package" command line, it will:

- Delete "/target" directory (clean goal)

- Look for source files in "/src/main/java" directory, compile them and put compiled files in "/target/classes" directory (compile goal, which always runs before package goal, like depend in Ant)

- Package files in "/target/classes" and "/src/main/resources" directories and put them all in a .jar file, which is stored in "/target" directory. (package goal)

You can reconfigure all directories by increasing the build script. But an "empty" script with only the project name and a few other tags also work.

If you need to import other JARs, like robocode.jar, then you need to declare them as dependencies, one-by-one in the pom.xml file. These JARs are searched in a "<home>/.m2/repository" directory, which is called a local repository. If they are not there, they are downloaded from a remote repository. By default, Maven downloads from the public Apache repository on internet, but it can be reconfigured as well. If you declare a dependency, but this dependency also needs another dependency, Maven discovers them for you by analyzing all pom.xml files from all JARs and download them all (recursive dependency resolution).

If you execute the same "empty" script with "mvn clean install" it will perform all the steps above and:

- After packaging, it will copy the .JAR file into the local repository, which can be used as dependency in other builds. (install goal)

If you need another JAR as dependency, which was never built in Maven, it can also be put in a repository with the lengthy command: "mvn install:install-file -Dfile=<jar name> -Dversion=<some version> -DartifactId=<dependency name> -DgroupId=<dependency group name>"

If you omit the "clean" goal, then the build tries to reuse existing files from a previous build to shorten build time (like Ant does).

There are other goals, but those are the essential ones.