Fundamentals of Java Beans and Servlet Management in Web Construction

1. CGS – 4854 Summer 2012 Instructor: Francisco R. Ortega Chapter 3 Part 1 Web Site Construction and Management

2. Today’s Lecture • Chapter 3 • Power Point + Board • It pays to attend class! • Remember I have office hours Today!

3. Member Variables • A servlet is a Java class • Accessible as long as the object is in memory • Accessible for the life of the servlet to any and all requests. • different users/clients.

4. Java Beans • Encapsulates other objects (data) into one • Makes data safer. • Makes it easier to move data around

5. Java Beans Specifications • Automatic operations on your objects • auto-generation from data stores, or vice versa • frameworks such as Hibernate to work with them • basically, the tools and frameworks exist that work with JavaBeans and make your life easier

6. A default (no argument) constructor • Must be serializable • All fields exposed with getters, setters • Default Validation using is

7. JavaBean conventions • The properties that are created in a bean are tied closely to the data in the edit page. • If the name of the input element is hobby, then the accessor and mutator in the property will be getHobbyand setHobby • Notice that the element name is lower case h, but the methods have upper case H.

8. In Class Question • Define a Java Bean with • playerName • playerSalary • How do you access the data in the jsp page? Hint: Expression Language

9. Setting the value • RequestData data = new RequestData(); • data.setPlayerName(request.getParameter(“playerName”));

10. Beans + JSP • To access the bean via the JSP, the bean data must be placed in the “SESSION”

11. Sessions • The session is a place that shared data can be placed. • Only a JSP or servlet can access the session. • Tomcat creates the session for each user/browser. • Each request has a separate session • Example: • Session session = request.getSession(); • session.setAttribute("refData", data);

12. The Big Picture

13. Tomcat (and others) • Tomcat is a multi-threaded application • When a servlet is loaded, it remains in memory • Each request for a servlet is handled by a new thread that it spawns (or pulled from a thread pool)

14. Avoiding Member Variables • Synchronization issues. • In class example

15. In Class - Java Review • Inheritance

16. Base Class import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class HelperBase { protected HttpServletRequest request; protected HttpServletResponse response; public HelperBase(HttpServletRequest request, HttpServletResponse response) { this.request = request; this.response = response; } }

17. Controller Helper public class ControllerHelper extends HelperBase{ protected RequestDataDefault data =new RequestDataDefault(); public ControllerHelper(HttpServletRequest request, HttpServletResponse response) { super(request, response); } public Object getData() { return data; } protected void doGet() { .... } }

18. doGet() protected void doGet() throws ServletException, IOException { request.getSession().setAttribute("helper", this); data.setHobby(request.getParameter("hobby")); data.setAversion(request.getParameter("aversion")); String address; if (request.getParameter("processButton") != null) { address = "Process.jsp"; } else if (request.getParameter("confirmButton") != null) { address = "Confirm.jsp"; } else { address = "Edit.jsp"; } RequestDispatcher dispatcher = request.getRequestDispatcher(address); dispatcher.forward(request, response); }

20. MVC • Model View Controller • Model: RequestData • View : JSP • Controller: ControllerHelper

21. More chapter 3 next week • Next Tuesday • Quiz about Chapter 3 and Chapter 2 • Start reading Chapter 4 for next week • Start preparing for Mid-Term Exam • You will be tested in Chapter 1 thru 4 • Maybe part of chapter 5. • More about this next week!

22. Office Hours • Remember that I switch my office hours for Tuesdays.