1. J2EE Overview Web Programming CSCI 4300

2. J2EE multi-tier architecture Servlet: Java class loaded into Web server JSP page: enhanced HTML page that is compiled into a servlet for deployment JavaBean: data holding class (part of Model in MVC)

3. J2EE Architecture Applets and special clients: downloaded, connect back to server Enterprise Java Beans: long-term, application- scope data storage and business logic

4. Web Application Layout

5. Mirroring packages with directories

6. Web Application Descriptor, web.xml Defines servlets and maps them to URL paths Declares the welcome file for the app Specifies pages or servlets to handle various errors Provides initialization parameters to servlets Provides links to external resources such as database connections

7. Web.xml prolog <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" http://java.sun.com/dtd/web- app_2_3.dtd>http://java.sun.com/dtd/web- app_2_3.dtd You can validate your web.xml using the W3C validator service (recommended1) When you change your web.xml, you must ask Chris or me to reload your web-app

8. Web.xml root element … web application contents. Can contain: –Servlet definitions –Servlet paths –Parameters –Etc, etc.

9. Servlet element GonzoServlet cs4300.Gonzo Or GonzoServlet gonzo.jsp

10. Servlet-mapping element GonzoServlet /gonzo If the web application root is http://ganesha.cs.uga.edu/myapp, http://ganesha.cs.uga.edu/myapp GonzoServlet is accessed at http://ganesha.cs.uga.edu/myapphttp://ganesha.cs.uga.edu/myapp/gonzo

11. Welcome page index.jsp Index.jsp is the file served at the URL http://ganesha.cs.uga.edu/myapp http://ganesha.cs.uga.edu/myapp

12. Error page elements 404 notFound.jsp org.xml.sax.SaxParseException parseError.jsp

13. Basic JSP page Declarations Java expressions Scriptlets (chunks of Java code) Try to minimize the mixing of HTML with Java (violates Model 2 architecture)

14. Declaration, scriptlet, and expression

15. Equivalent HTML from previous 1 Michael Adams 2 Dan Everett 1 Hunter Thompson But note that we try to avoid such mixing of Java and HTML!

16. Model 2 Architecture (MVC)

17. Helper Object Scopes

18. JavaBean Helper class that holds information Separates Java code from HTML Implements Model component of MVC architecture Useful for holding session data

19. JSP Address Book Interface

20. JavaBean Example Store functionality: user enters name -email pair for storage in bean Fetch functionality: user enters name, bean replies with email

21. JSP-Bean communication Make element names in JSP correspond to variable names in Bean Write Bean class with setX() and getX() setter and getter methods sends inputs to Bean gets values from Bean

22. Acknowledgements J2EE architecture diagrams: Sun J2EE tutorial, http://java.sun.com/j2ee/1.4/docs/tutorial/doc/index.html http://java.sun.com/j2ee/1.4/docs/tutorial/doc/index.html Object scopes: jGuru Java Server Pages fundamentals, http://java.sun.com/developer/onlineTraining/JSPIntro/contents.html#JSPIntro6_3