Hello Ulrich,
You are right.
1. The error messages that I posted were coming in the Error Log of Eclipse when I right clicked on the project and selected Run As --> Java Application. I guess that is using the neo-java-web-sdk and not HCP but I am still wondering why it cannot resolve the packages.
2. Regarding HCP, the code I have written (to be honest copied from the tutorial) is a Java servlet. I guess starting the application on HCP (by going to Java applications) should be enough. However, I do not get any error. (I expect to get an error as I have just used the ABAP destination in the code, but not yet defined the destination in HCP).
3. You asked for the code sample. It all there in this tutorial link under the section "Creating a sample servlet".