What is Maven and how do I install it?

MavenSW, located at http://maven.apache.org, is a great JavaSW project build and management tool from the ApacheSWSoftware Foundation. One primary focus of Maven is as a build tool, performing tasks similar to AntSW, although it's more like Ant on steroids.

A very significant aspect of Maven is the use of repositories to manage jarW files across different projects. In a simple software development environment, you may work on a project and check jar files directly into your project in your version control system, and you may do this in each project that you work on. This system works fine in relatively simple situations, but it becomes unweildy as projects grow in size, in complexity, and in their numbers of developers. In the Maven system, jar files are stored in remote repositories, and they are downloaded to your local machine to a local repository as needed. Typically, these same jar files are accessed across projects, and Maven makes it very simple to manage different versions of jar files, and to group together sets of related jar files. Building different types of projects (such as jars, wars, and ears) is handled very cleanly by Maven. Maven can perform tasks such as generate useful documentation about your project. The features of Maven go on and on.

Maven 2 is very significantly different from Maven 1. This tutorial will cover Maven 2.

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To set up Maven, you need to:

1. Download Maven and unzip it
2. Create a JAVA_HOME System Variable
3. Create an M2_HOME System Variable
4. Add %JAVA_HOME%\bin;%M2_HOME%\bin; to your System Path

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To begin with, download the latest Maven from http://maven.apache.org/download.html. I downloaded apache-maven-2.0.8-bin.zip and extracted it to C:\dev\apache-maven-2.0.8.

Go to your System Properties → Environment Variables.

Create a JAVA_HOME System Variable and point it to your Java installation. I pointed mine to C:\dev\jdk1.6.0_04.

Create an M2_HOME System Variable and point it to your Maven installation. I pointed mine to C:\dev\apache-maven-2.0.8.

You should now have JAVA_HOME and M2_HOME System Variables.

Add %JAVA_HOME%\bin;%M2_HOME%\bin; to your Path System Variable. This puts your Java and Maven executables in the System Path so that they can be executed without their fully qualified paths.

Open a command prompt window, and at the command prompt, type 'mvn -version'. You should see a message displaying the version of MavenSW and the version of JavaSW.

Next, at the command prompt, try typing a command like 'mvn clean'. You'll probably see that some jarW files downloaded from the Maven central repository to your machine. After that, we see a 'BUILD ERROR'. This message is fine. This is telling us that we ran the command but that there was no pom.xml file present in the directory where we ran the command.

After running the 'mvn clean', if we go to our user home directory (for me, C:\Users\Cakes), we can see that an .m2 directory has been created by mavenSW. Within .m2, we can see a 'repository' directory. This is the default location for your local maven repository. This local repository directory contains things such as the jar files that your projects use. In addition, it contains the jar files and things that maven itself needs. When we ran the 'mvn clean' command, we asked maven to do a 'clean' command, which requires the maven-clean-plugin jar file. If you look back at the command prompt output after the 'mvn clean' command, you can see that the maven-clean-plugin jar file was downloaded, since maven realized that it needed this jar file in order to do the 'clean'.

If we examine the contents of our local maven repository, we can see that it contains the maven-clean-plugin jar file. On my machine, the jar is located at C:\Users\Cakes\.m2\repository\org\apache\maven\plugins\maven-clean-plugin\2.2.

Our Maven is installed and working. We can now get to work creating projects with this great tool.