title: How to handle Maven missing artifact errors?
body: <p>I've just recently started doing Java development and I picked up Maven2 for dependency management and project task automation.</p>
  
  <p>One peculiar issue I've stumbled upon, that I haven't been able to fully understand, is that for certain artifacts you need to configure exclusions for their dependencies, otherwise you get a Maven <code>Missing artifact groupId:artifactId:version:lifecycle</code> error. I've tried creating a Spring MVC project from the supplied STS Spring project templates and the Maven POM contained exclusions for <strong>log4j</strong>, which, when removed, would produce an error. </p>
  
  <p>So what do I do when I manually add a dependency and get the missing artifact error for some of it's dependencies. Do I just jump and add them to the list of exclusions or should I be more careful about it? </p>
  
  <p>And why does this happen? I'm assuming it may be perhaps that an artifact has a dependency of a certain version and another artifact has the same dependency of a different version, where both can't exist on the <code>classpath</code> or is it something else I'm missing?</p>