4/10/03 CSE 403

CSE 403: Servlet Technology

Zach Crisman (zcrisman@cs)

Shane Cantrel (shanec@cs)

4/10/03

4/10/03 CSE 403

CGI (Common GatewayInterface) vs Servlets

n Separate Processfor each connection

n No StandardLibraries/Languages

n State not savedbetweenconnections

n One Serlvet EngineProcess

n JavaLibraries/Language

n State saved untilservlet destroyed

4/10/03 CSE 403

Tomcat & How We Will BeUsing it

n Official Reference Implementation of JavaServlet Technology

n A Servlet Engine & Normal Webservern Everyone will be running an different instance

of Tomcat on a different port numbers(‘81’+instance number)

n Will install war (Web Application Resource)files via Tomcat management tasks in Ant

4/10/03 CSE 403

Where do I find this stuff?/*For generic , protocol independent servletfunctionality*/

import javax.servlet.*;

/*For servlets that will use the http protocol(WWW Based)*/

import javax.servlet.http.*;

Tutorial @http://java.sun.com/webservices/docs/1.0/tutorial/doc/Servlets.html

API @http://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/servlet/package-summary.html

Tomcat: Kick Start by Bond & LawFocus on Chapters 1,3,4,6 for this assignment (Don’t worry about JPS stuff)

4/10/03 CSE 403

GenericServlet

n ProtocolIndependent

n Overrideservice()whenextended

n Must write one’sown means ofhandling requests

Image from Java ServletProgramming by Jason Hunter

4/10/03 CSE 403

HttpServletn ExtendsGenericServlet()

n Overide doGet(…) &doPost(…)

n Already understandshttp

n Majority of servletsextend Image from Java Servlet

Programming by Jason Hunter

4/10/03 CSE 403

HttpServlet Skeletonimport javax.servlet.*;

import javax.servlet.http.*;

public class ServletSkeleton extends HttpServlet {public void doGet(HttpServletRequest req,

HttpServletResponse res)throws ServletException, IOException {}

public void doPost(HttpServletRequest req, HttpServletResponse res)

throws ServletException, IOException {}}

4/10/03 CSE 403

GET vs POST

GET

- retrievinginformation

- html/images

- parameters listed inURL

POST

- send information

- uploads/forms

- parameters hiddenwithin header

4/10/03 CSE 403

Servlet Lifecyclen Timing of Lifecycle not specified

by serlvet specn Servlet may be destroyed/

instantiated when you leastexpect itinit() only called once in lifecycle

n Multi-threaded environmentn destory() should not only free

resources but also save statethat will be required in anotherinstance

n A servlet is only a instance of aclass that is dynamically loadedinto the servlet engine (Tomcat)

4/10/03 CSE 403

Database Info

n PostgreSQL 7.3 installed on rockhopper &adeliehttp://www.postgresql.org/docs/

n JDBC interface will be installedn Tomcat: Kick Start, ch 9 (general using

databases w/ Tomcat)n Everyone will have accounts already setup on

the DB systemn w/ database concurrency is not a problem

when storing data

4/10/03 CSE 403

Web Setup

n MIME Settingsn .jad

n text/vnd.sun.j2me.app-descriptor

n .jarn application/java-archive

n The settings are preset on Tomcat, butnot on other servers.

n http://hydrus.net/midlets

4/10/03 CSE 403

Downloading the Midlet

4/10/03 CSE 403

Running the Midlet

Noticeunpredictable

errors