bug fix: resolve the "No Session found" error.
the reason is after an Action which is annotated to JSON type execute it's request method, struts framework will call all it's get perfix method, when it call the method getXXXService which is dynamic inject by Spring, the program will broken.
bug 1: "No Session found" , remove the get method fo XXXService or XXXDAO, both fields will be injected by Spring.
bug 2: the request method will execute two times when one request come, remove or modify the getJSON method which is used in jquery-struts2 example. At this time, I just remove it.