1 / 22

J2EE Overview

J2EE Overview. Web Programming CSCI 4300. 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). J2EE Architecture.

bud
Download Presentation

J2EE Overview

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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 <?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" 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-app> … web application contents. </web-app> • Can contain: • Servlet definitions • Servlet paths • Parameters • Etc, etc.

  9. Servlet element <servlet> <servlet-name>GonzoServlet</servlet-name> <servlet-class>cs4300.Gonzo</servlet-class> </servlet> Or <servlet> <servlet-name>GonzoServlet</servlet-name> <jsp-page>gonzo.jsp</jsp-page> </servlet>

  10. Servlet-mapping element <servlet-mapping> <servlet-name>GonzoServlet</servlet-name> <url-pattern>/gonzo</url-pattern> </servlet-mapping> If the web application root is http://ganesha.cs.uga.edu/myapp, GonzoServlet is accessed at http://ganesha.cs.uga.edu/myapp/gonzo

  11. Welcome page <welcome-file-list> <welcome-file> index.jsp </welcome-file> </welcome-file-list> • Index.jsp is the file served at the URL http://ganesha.cs.uga.edu/myapp

  12. Error page elements <error-page> <error-code>404</error-code> <location>notFound.jsp</location> </error-page> <error-page> <exception-type> org.xml.sax.SaxParseException </exception-type> <location>parseError.jsp</location> </error-page>

  13. Basic JSP page <%@ page contentType="text/html; charset=UTF-8" %> <html> <head> <Static HTML code…> • 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 <%! int i; String[] userName %> <table border=1> <% for (i=0;i<userName.length;i++) { %> <tr><td><%=i+1 %> </td> <td> <%=userName[i] %> </td></tr> <% } %> </table>

  15. Equivalent HTML from previous <table border=1> <tr><td>1</td><td>Michael Adams</td></tr> <tr><td>2</td><td>Dan Everett</td></tr> <tr><td>1</td><td>Hunter Thompson</td></tr> </table> • 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 <INPUT> element names in JSP correspond to variable names in Bean • Write Bean class with setX() and getX() setter and getter methods • <jsp:setProperty> sends inputs to Bean • <jsp:getProperty> gets values from Bean

  22. Acknowledgements • J2EE architecture diagrams: Sun J2EE tutorial, 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

More Related