Green Beans: Getting Started with Maven and Spring
Apache Maven is a popular open source tool that offers a convention-over-configuration approach to project build management. Indeed the Eclipse Community Surveys show Maven increased its adoption from 8% in 2009 to 28% in 2010, underscoring its usefulness in a wide range of project settings. Even though you can use Spring without using Maven, there are many reasons to recommend its use to Spring developers. In this post I'll show you how to get started using Maven, and how to use it successfully with Spring libraries, repositories and tooling like SpringSource Tool Suite and Spring Roo.
Maven handles project builds. Maven can provide a lot of power and sophistication with relative ease if your project follows Maven's conventions. It is declarative; you describe what you want done, not how you want it done. This approach will seem different if you've come from venerable build tools like Make, or Ant.
You declare your project's dependencies in the Maven project configuration. These dependencies are then resolved on your behalf and downloaded for you. This is similar to the package system found in many different operating systems. Suppose you're using OS X's fink or ports command line tools. To update an operating system's a functionality, a user selects a package (say, the latest security patches, or a new version of the glib library) to install in an administration client and then instruct the client to downloaded and install it from well-known servers, referred to as package repositories. When the package is downloaded, the package manager consults the package's manifest which enumerates all the libraries (found in other packages) that the package depends on - its transitive dependencies. Those too are downloaded.
There are several ways to install Maven If you haven't already got it installed. Download it from the Apache web site. Choose a more recent version. Currently, many people are using Maven 2.21, or the recently released Maven 3. Download the version you'd like to use and then unzip it to a directory of your choice. Alternatively, several operating systems provide Maven 2 builds (and soon, Maven 3 builds) in the package system. For example, on Ubuntu, you can run sudo apt-get install maven2 . If you're using the SpringSource Tool Suite (available here for download for free), then you don't need to worry, Maven's already downloaded and included in your STS installation folder. Regardless of how you get the Maven binaries on your system, ensure that the binary is on your operating system's search path. Usually, this is just a matter of adding the Maven installation's bin folder to your operating system's PATH variable. It's also a good practice to create a system variable for the Maven installation itself, called MAVEN_HOME. On a Unix (including OS X) or Linux machine, this setup looks about the same. On my machine (an Ubuntu Linux machine), it looks like this:
export MAVEN_HOME=/home/jlong/bin/springsource/maven-2.2.1.RELEASE export PATH=$PATH:$MAVEN_HOME/bin
To test it, open up a new shell and issue the following command:
mvn --version
You should see some output confirming the command presence on your system, like this:
jlong@jlong-mbp:~/Desktop/code$ mvn --version Apache Maven 2.2.1 (r801777; 2009-08-06 12:16:01-0700) Java version: 1.6.0_22 Java home: /usr/lib/jvm/java-6-sun-1.6.0.22/jre Default locale: en_US, platform encoding: UTF-8 OS name: "linux" version: "2.6.35-22-generic" arch: "amd64" Family: "unix" jlong@jlong-mbp:~/Desktop/code$
Getting Started With Maven
Maven projects assume a standard directory structure, which looks - at a minimum - like this:
./pom.xml ./src ./src/main ./src/main/java ./src/main/resources ./src/test ./src/test/java ./src/test/resources
At the root of the directory structure is a XML file (always called pom.xml) that Maven expects. The pom.xml (POM is short for Project Object Model) describes the things specific to your project that can't be inferred automatically like dependencies, the name of the project, etc.
| Directory | Description Directory's Contents (relative to the project root) |
|---|---|
| src/main/java | Contains the Java source code for your project |
| src/main/resources | Contains any classpath-relative resources for your project (like, a Spring application context .xml file) |
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