developing and debugging CAS in eclipse
I'm new to CAS development, but here's how I was able to get CAS up and running in eclipse:
1. Download CAS source repos:
   svn checkout https://source.jasig.org/cas-clients/java-client/tags/cas-java-client-3-1-10-final/ cas-client-3.1.10
   svn checkout https://source.jasig.org/cas3/tags/cas-server-3.4.2.1/ cas-server-3.4.2.1
2. Perform Maven2 builds:
   cd cas-client-3.1.10
   mvn package install
   cd ../cas-server-3.4.2.1
   [to authenticate against LDAP: add a "cas-server-support-ldap" dependency in cas-server-webapp/pom.xml]
   mvn package install
3. Test the generated WAR file in Tomcat (a sanity check to ensure default functionality):
   cas-server-3.4.2.1/cas-server-webapp/target/cas.war
4. Prepare the Eclipse IDE
   Download and install Eclipse "Ganymede"
   Install m2eclipse plugin for Maven
   Import the cas-server-core, cas-server-ldap and cas-client-core projects from your svn repos:
      file > import > "existing maven projects"
   Create new empty "dynamic web project" in eclipse. Call it something like "CASWebappProject", for example.
5. Link the eclipse project to your local svn directory
   In the WebContent directory, delete the generated WEB-INF subdirectory
   In the WebContent directory, create the following symbolic links to the CAS source in your local svn directory:
      ln -s <for each path to maven src listed below>
      ..cas-server-3.4.2.1/cas-server-webapp/src/main/webapp/css
      ..cas-server-3.4.2.1/cas-server-webapp/src/main/webapp/images
      ..cas-server-3.4.2.1/cas-server-webapp/src/main/webapp/js
      ..cas-server-3.4.2.1/cas-server-webapp/src/main/webapp/themes
      ..cas-server-3.4.2.1/cas-server-webapp/src/main/webapp/WEB-INF
      ..cas-server-3.4.2.1/cas-server-webapp/src/main/webapp/favicon.ico
      ..cas-server-3.4.2.1/cas-server-webapp/src/main/webapp/index.jsp
   In the CASWebappProject src directory, create a symbolic link to the svn source packages:
      ..cas-server-3.4.2.1/cas-server-webapp/src/main/java/org
   Copy the POM dependencies from Maven "target" into the web project library:
      cd into the WEB-INF directory
      cp -R ..cas-server-3.4.2.1/cas-server-webapp/target/cas-server-webapp-3.4.2.1/WEB-INF/lib/ .
   In Eclipse, use the "New Server" wizard to create a new "Server" project.
   Add the CASWebappProject to the server configuration
   Modify the WEB-INF/classes/log4j.xml so the the cas.log and perfStats.log file paths map to a permissible location
   In the CASWebappProject project, add the other projects to the build path
6. Right-click the CASWebappProject and "run as > run on server".
7. Source code changes you make in eclipse will be reflected in your local svn directory