Running without using jars in the classpath

The Exec plugin makes it possible for us to run the simplest weather program without having to load the appropriate dependencies into the classpath. In any other build system, we would have to copy all of the program dependencies into some sort of lib/ directory containing a collection of JAR files. Then, we would have to write a simple script that includes our program’s bytecode and all of our dependencies in a classpath. Only then could we run java org.sonatype.mavenbook.weather.Main. The Exec plugin leverages the fact that Maven already knows how to create and manage your classpath and dependencies.

mvn exec:java -Dexec.mainClass=org.sonatype.mavenbook.weather.Main \
      -Dexec.args="70112"

This is convenient, but it’s also nice to know exactly what is being included in your project’s classpath. Although the project depends on a few libraries such as Dom4J, Log4J, Jaxen, and Velocity, it also relies on a few transitive dependencies. If you need to find out what is on the classpath, you can use the Maven Dependency plugin to print out a

mvn dependency:resolve

  

mvn dependency:tree