1. Introduction to Java Servlets on Jakarta Tomcat
Novell BrainShare 2002
Introduction to Java Servlets on Jakarta Tomcat
Moises Morales
Software Engineer
Novell, Inc.
DCB124—Introduction to Java Servlets on Jakarta Tomcat

2. Introduction Goals of the session one Net
Novell BrainShare 2002
Introduction
Goals of the session
Learn about Java servlets: Their architecture, uses, and how to write them*
Learn about Jakarta Tomcat Servlet Gateway
*Some background of Java programming is expected
one Net
The servlet technology is Java-based and cross-platform, making it possible to run of different networks more securely and efficiently and powering the web by giving solutions for eCommerce
DCB124—Introduction to Java Servlets on Jakarta Tomcat

3. Vision…one Net Mission
Novell BrainShare 2002
Vision…one Net
A world where networks of all types—corporate and public, intranets, extranets, and the Internet—work together as one Net and securely connect employees, customers, suppliers, and partners across organizational boundaries
Mission
To solve complex business and technical challenges with Net business solutions that enable people, processes, and systems to work together and our customers to profit from the opportunities of a networked world
DCB124—Introduction to Java Servlets on Jakarta Tomcat

5. Origin of Servlets: How They Started
Novell BrainShare 2002
Origin of Servlets: How They Started
Java applets vs. servlets
Applets are Java programs which can be embedded directly into the webpages to add more functionality
Applet gets downloaded to the client and then executed when we hit a web page with it
If the size of applet grows, it increases download time and is inefficient
Applets are also dependent on browsers
The output can look different, raising compatibility issues
If an applet is changed to be server-side, then it is executed on the server rather than the client
This can avoid the aforementioned drawbacks
Java servlets are like applets, not as graphical but executed on the server
DCB124—Introduction to Java Servlets on Jakarta Tomcat

6. Origin of Servlets (cont.)
Novell BrainShare 2002
Origin of Servlets (cont.)
CGI vs. servlets
Common Gateway Interface (CGI), traditionally used for developing web applications
CGI is server-side and the web server creates a process to listen to requests, which are processed and send back to the server, then replied to the client
With each CGI request, as new process is created and this could be cumbersome when there are too many requests
Wastes of resources and slows the response time
Browser could timeout if the CGI request abnormally terminates, as they run on different process than the web servers
Java servlets can accomplish all the tasks of CGI more efficiently
Servlets have session tracking built in
DCB124—Introduction to Java Servlets on Jakarta Tomcat

7. What are Servlets?
Servlets are dynamically-loaded Java modules that extends the functionality of a web server by taking requests from the client and executing them on the server
Java servlets runs fully inside the JVM
JVM
Request
Client/ browser
Server
Servlet
Response

8. Why Servlets? Uses Practical application Portable Efficient Secure
Robust
Integration
Practical application
eCommerce

9. Servlet Architecture Servlets are based on two main packages
Novell BrainShare 2002
Servlet Architecture
Servlets are based on two main packages
javax.servlet
javax.servlet.http
GenericServlet
HttpServlet
This class is extended from GenericServlet class
DCB124—Introduction to Java Servlets on Jakarta Tomcat

10. Servlet Architecture (cont.)
Novell BrainShare 2002
Servlet Architecture (cont.)
Lifecycle of a servlet
init()
This method is called as soon as the servlet is instantiated
service()
This method then handles the client requests
destroy()
To mark the end of the servlet, for example, when the servlet service is completed, this method is used
DCB124—Introduction to Java Servlets on Jakarta Tomcat

11. Hello World Example import java.io.*; import javax.servlet.*;
Novell BrainShare 2002
Hello World Example
import java.io.*;
import javax.servlet.*;
import javax.servlet,http.*;
public class HelloWorld extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println(“Hello World!”); }
DCB124—Introduction to Java Servlets on Jakarta Tomcat

12. Then What Are JSPs? Java server pages
Novell BrainShare 2002
Then What Are JSPs?
Java server pages
Java technology to create dynamic HTML on server-side
Lets you combine static and dynamic HTML
It is actually servlet code embedded on the page
It is easier to use JSP when there is a lot of HTML used as it can be cumbersome to have the println statement generate HTML
Behind the scenes, when a Java server page is hit, the server automatically creates, compiles, and runs servlet object
Servlets can do anything that JSPs can accomplish
DCB124—Introduction to Java Servlets on Jakarta Tomcat

13. Java Servlet Development Kit (JSDK)
Novell BrainShare 2002
Java Servlet Development Kit (JSDK)
To use Java servlets, the JSDK is needed along with a capable servlet web engine
The JSDK 2.x is available for download from
DCB124—Introduction to Java Servlets on Jakarta Tomcat

14. Popular Servlet and JSP Engines to Run on Novell NetWare® Server
Novell BrainShare 2002
Popular Servlet and JSP Engines to Run on Novell NetWare® Server
Jakarta Tomcat
Tomcat runs on Apache server, but can be integerated with NetWare Enterprise Web Server
IBM WebSphere
Shipped with NetWare 5.1
GNU JSP
Jetty
Novell Servlet Gateway
Supports only the old servlet specification 2, to be discontinued soon
DCB124—Introduction to Java Servlets on Jakarta Tomcat

15. Jakarta Servlet Engine (Tomcat)
Novell BrainShare 2002
Jakarta Servlet Engine (Tomcat)
Jakarta is an Apache project
Tomcat is one of its subprojects
Tomcat is the official reference implementation for the Java servlet and JavaServer pages technologies (according to Sun’s specifications)
Tomcat is developed in an open and participatory environment and released under the Apache software license
DCB124—Introduction to Java Servlets on Jakarta Tomcat

16. Downloading the Jakarta Software
Novell BrainShare 2002
Downloading the Jakarta Software
Current and previous versions of Jakarta are available
Jakarta is downloadable as source code or binary
Supported platforms include NetWare, UNIX, Linux, Windows, and others
DCB124—Introduction to Java Servlets on Jakarta Tomcat

17. Download the Jakarta Software
Novell BrainShare 2002
Download the Jakarta Software
To get the binaries, download the following files
Released Java binaries—jakarta-tomcat-3.3.zip
Released NetWare Apache module—mod_jk.nlm
Additional connectors
nsapi_rd.nlm—enterprise server connector
jni_conn.nlm—JNI connector
DCB124—Introduction to Java Servlets on Jakarta Tomcat

18. Download the Jakarta Software
Novell BrainShare 2002
Download the Jakarta Software
To build the source, download the following files
Released source code—JAKARTA-TOMCAT-3.3-SRC.ZIP
Unpack JAKARTA-TOMCAT-3.3-SRC.ZIP to an appropriate directory and read README to get additional components necessary for building
Metrowerks Code Warrior 5 or later is required for building the native connectors
DCB124—Introduction to Java Servlets on Jakarta Tomcat

19. Configuring Jakarta/Tomcat
Novell BrainShare 2002
Configuring Jakarta/Tomcat
General configuration in tomcat\conf\server.xml
General web server connector configuration in tomcat\conf\workers.properties
Tomcat can auto-generate an Apache configuration file that can be included in HTTPD.CONF
tomcat\conf\mod_jk.conf-auto
Tomcat must be started before Apache for this file to be created and have correct information
DCB124—Introduction to Java Servlets on Jakarta Tomcat

20. Adding Additional Servlets, JSPs, and Web Applications
Novell BrainShare 2002
Adding Additional Servlets, JSPs, and Web Applications
Individual servlets can be placed in TOMCAT_HOME\webapps\ROOT\WEB-INF\classes
Additional contexts are created under the TOMCAT_HOME\webapps directory
Each directory becomes its own context
Behavior for a context is defined by the WEB-INF\WEB.XML file
Jakarta uses Web Application Archive (WAR) files
.WAR files are automatically extracted during startup
An appropriate context is created
DCB124—Introduction to Java Servlets on Jakarta Tomcat

21. Hands-On
Hello World
Session Test

22. Hello World Example import java.io.*; import javax.servlet.*;
Novell BrainShare 2002
Hello World Example
import java.io.*;
import javax.servlet.*;
import javax.servlet,http.*;
public class HelloWorld extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println(“Hello World!”); }
DCB124—Introduction to Java Servlets on Jakarta Tomcat

23. Need More Help? There are a lot of online Java resources at
Novell BrainShare 2002
Need More Help?
There are a lot of online Java resources at
Novell Developer Kit (NDK) site at
Open a incident with Novell Developer Support (free of charge for internal developers)
Newsgroups on the NDK site
More questions? Send me an at
DCB124—Introduction to Java Servlets on Jakarta Tomcat