Advanced Java Class Web Applications – Part 0 (Introduction)

Intro to Web Apps web apps vs. web sites –server-side processing web apps vs. network programming –takes advantage of abstractions that cover communications layer, security, etc. –requires web server & application server & web client software Webs app API is part of J2EE

Web technology See figure 13-1 on page 815 for a “cleaner” version.

HTTP and HTTPS protocols "S" is for secure An exchange = request & response Each exchange is independent ("stateless") HTTP request methods –GET – put form values in URL (visible, limited length) –POST – put form values in embedded header (invisible, any length)

URLs, Identifiers, and Names protocol://domainName[:port]/resourceName –resourceName: folder path & file protocols: HTTP, HTTPS, FTP, etc. domain Name: host Name, IP address, etc. port; default for HTTP=80, HTTPS=443

HTML & XHTML Documents XML is strict (grammatically) HTML has all the popular mark-ups XHTML is both (therefore preferred)

Servlets Inside a web-app, on the server-side Generally "alive" while web app is alive Respond to HTTP requests

View–Controller–Model Layers View – Web pages shown on client side Controller – Servlet (server-side class) Model – Other server side classes –access DB, server-side files –security-sensitive tasks –processor-heavy operations –network communications

Digital Flashcards Example Activity 1.Divide each task into subtasks. 2.Which subtasks should be done at each level of the application (VMC), and what file type or Java object should be responsible for the subtask? Tasks: Logging in a user Allowing a user to enter a new word Quizzing a user on a list of words and recording the results.