1. http protocol Response-request Clients not limited to web browsers. Anything that can access code implementing the protocol works: –Standalone programs in Java Perl C, C++ Javascript PHP Lisp …

2. http protocol Requests: –GET –POST –HEAD GET originally designed for request to provide a resource (the part after the http:// / Extended with CGI query syntax

3. GET vs Post: CGI Query Sytax GET –uses CGI http://…../db?arg1=val1&arg2=val2&… –Issues: data is exposed only good for small data POST –Arbitrary data can be sent to server including plain text serialized objects …

4. http Responses Headers can include data about –Content Format MIME Content types text/html text/xml application/msword application/jpeg application/gif application/mpeg …

5. http Responses Headers can include data about –Content Format –Cache control (e.g. how long cache will be valid) –Length of message –Last Modification Date

6. Server side programming In the old days (circa 1993-1998) most server side programming was perl using the cgi interface libraries, processing GET Generalizations in Java: –Servlets. Classes wrap most of the protocol. servlet implements doGet and doPut –JSP (client side) builds servlets on-the-fly. –Need to be embedded in a web container implementing the servlet API, e.g. Apache jakarta tomcat, JServ (somewhat obsolete), and commercial products

7. Tomcat Web container Embeddable in web servers such as Apache Can run standalone (which is what we'll do). In other words, it also can do http protocols. In fact when embedded in a webserver, the server forwards the http requests and responses. (Part of web container spec?)