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Now sit back while the M2E logic tries to scan the POMs of all the subprojects and downloads the dependency JAR files from the internet. If you get a missing dependency for a Yale JAR file, then the $HOME/.m2/settings.xml file does not point to the Artifactory server where Yale stores its JAR files. You can ignore error messages about XML file syntax errors. In the Luna version of Eclipse, the M2E support discovers that CAS uses AspectJ and offers to install support for AspectJ in Eclipse. When you are done, there may still be a few error messages but they should not be important.
A Maven project has standard source directories (src/main/java) used to build the output JAR or WAR artifact. A Maven POM has "dependency" declarations it uses to download JAR files (to your local Maven repository) and build a "classpath" used to find referenced classes at compile time. Eclipse has a "Build Path" (physically the .classpath file) that defines source directories, the location where the ouput class files are stored, and the libraries that have to be used to compile the source. M2E runs through the POM files in each subproject and creates a Eclipse project with a Eclipse Build Path that tells Eclipse to do exactly the same thing Maven would do to the same project. Eclipse will compile the same source in the same source directory and produce the same output to the same output directory using the same JAR libraries to run the compiler. It is important (because it answers questions later on) that you understand that Eclipse is being configured to do MOSTLY the same thing that Maven would do, but Eclipse does it without running Maven itself. The MOSTLY qualification is that M2E sets default values for the enormous number of options that an Eclipse project has (what error message to display or hide, syntax coloring, everything else you can set if you right click the project and choose Preferences from the menu). After M2E creates an initial default batch of project setting, you are free to change them and ask Eclipse to do things slightly different without breaking the development process.
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Interactive and Batch Modes
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Eclipse tries to make J2EE development simpler than is reasonably possible. Eclipse is almost successful, close enough so that it is quite usable as long as you realize what cannot possibly be made to work exactly right and solve that problem with another tool.
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