What makes Seam so cool is its ability to direct traffic behind the scenes, in this case by holding the selected course in context while you move from page to page.
Doing so ensures Seam will not complain when it cannot find a course object to inject.
这样做可以确保Seam在找不到要注入的课程对象时不会发出警报。
3
Now that you have a clean way to retrieve the list of courses and maintain that data in a context variable managed by Seam, it is time to branch off from the course listing.