Maven Quick References

In the parent POM, the main difference between the <dependencies> and <dependencyManagement> is this:

Artifacts specified in the <dependencies> section will ALWAYS be included as a dependency of the child module(s). Artifacts specified in the <dependencyManagement> section, will only be included in the child module if they were also specified in the <dependencies> section of the child module itself. Why is it good you ask? because you specify the version and/or scope in the parent, and you can leave them out when specifying the dependencies in the child POM. This can help you use unified versions for dependencies for child modules, without specifying the version in each child module

Example, a parent project (Pro-par) defines a dependency under the dependencyManagement:

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8</version>
    </dependency>
 </dependencies>
</dependencyManagement>

Then in the child of Pro-par, I can use the junit :

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
    </dependency>
 </dependencies>

Dependency Management allows to consolidate and centralize the management of dependency versions without adding dependencies which are inherited by all children. This is especially useful when you have a set of projects (i.e. more than one) that inherits a common parent. Another extremely important use case of dependencyManagement is the control of versions of artifacts used in transitive dependencies. This is hard to explain without an example. Luckily, this is illustrated in the documentation. You still need to define them in the child POM to show that you are using them. They are not actually included in the child projects just because they are in <dependencyManagement> in the parent POM. Enclosing dependencies in <dependencyManagement> centralizes management of the version, scope, and exclusions for each dependency, if and when you decide to use it. Maven's guide to dependency management gets into all the details.