Building Web Applications Using Servlets

1
IA308 Servlets and JSPs
Christophe Coenraets Manager, Technical
Evangelists Internet Applications
Division ccoenrae_at_sybase.com
2
Servlets Topics

• Dynamic Web Sites Architectures
• Servlets Benefits
• Servlet's Life Cycle
• Building a Servlet
• Tracking Sessions

3
Site Map
ListDest.jsp
Destination.jsp
TripFinder.jsp
LogonServlet
Logon.htm
Payment.jsp
LogonError.htm
Booking.jsp
Customer.jsp
4
Static Web Site
http//www.myvacation.com/ListDest.htm
HTTP Server
HTTP
HTML
5
Dynamic Page Generation Using CGI
http//www.myvacation.com/cgi/ListDest.exe
CGI Application
HTTP Server
ODBC / Native
HTTP
HTML
6
Dynamic Page GenerationUsing Servlets
http//www.myvacation.com/servlet/ListDest
Servlet Container
HTTP Server
JDBC
HTTP
HTML
7
What is a Servlet?

• Server side Java program that extends the
  functionality of a Web Server
• Used to dynamically generate HTML documents
• Comparable to
• CGI
• Netscape NSAPI
• Microsoft ISAPI
• Apache Modules

8
Servlets Benefits

• Written in pure Java
• Platform independent
• Can take advantage of JDBC, EJB, JMS, JavaMail,
  JavaIDL, RMI, ...
• Server independent
• Scalability
• Dont start new process for each request
• Can run in same server process as HTTP server
• Multi-threaded

9
Building a ServletUsing the Servlet API

1. Extend HttpServlet
2. Code Servlet's life cycle Methods

Servlet
GenericServlet
HttpServlet
LogonServlet
10
Servlet Life Cycle
Servlets Container
HTTP Server
init( )
11
Servlet Life Cycle
Servlets Container
HTTP Server
init( )
doGet( )
Servlet
12
Servlet Life Cycle
Servlets Container
HTTP Server
init( )
doGet( )
Servlet
13
Servlet Life Cycle
Servlets Container
HTTP Server
init( )
doGet( )
destroy( )
Servlet
14
Servlet Life Cycle
Servlets Container
HTTP Server
15
Advanced Servlet Support in PowerJ 3.6

• Java Servlet 2.2 wizard
• Generates Servlet class
• Deployment descriptors
• Web Archive (WAR) target (optional)
• Design time visual class for drag-and-drop
  programming
• Automated deployment
• Remote debugging

16
Advanced Servlet Support in EA Server 3.6

• Access to connection caches
• Configurable threading model
• Access to external parameters
• Inter-server component invocations
• Refresh
• Remote debugging
• Logging support

17
Building the Logon ServletDemo
ListDest.jsp
LogonServlet
Logon.htm
LogonError.htm
18
Servlets as Part of J2EE

• Contribution
• Provides platform/server independent and scalable
  architecture for developing HTTP-based
  applications
• Limitations
• Modification of static content requires
  recompilation
• Business logic not reusableby non Web clients

Addressed by JSP
Addressed by EJB
19
Java Server PagesTopics

• JSP Architecture
• Anatomy of a JSP
• Directives
• Scripting Elements
• Standard Action Tags

20
Site Map
ListDest.jsp
Destination.jsp
TripFinder.jsp
LogonServlet
Logon.htm
Payment.jsp
LogonError.htm
Booking.jsp
Customer.jsp
21
Dynamic Page GenerationUsing Servlets
http//www.myvacation.com/servlet/ListDest
Servlet Container
HTTP Server
JDBC
HTTP
HTML
EA Server
22
Dynamic Page GenerationUsing Java Server Pages
(JSP)
http//www.myvacation.com/ListDest.jsp
JSPEngine
HTTP Server
JDBC
HTTP
HTML
Servlet Container
EA Server
23
Java Server Pages

• Web scripting technology
• Creation of dynamic content using static
  templates
• Combine markup (HTML or XML) with Java Code to
  produce a dynamic Web Page
• Similar to Microsoft ASP and PowerDynamo
• Uses Java as its scripting language
• Full power of the Java language
• Simple tags allow non Java developer to generate
  dynamic content

24
A Simple JSP

• lthtmlgt
• ltbodygt
• lt_at_ page language"java" import"" gt
• ltH1gtWelcome back,
• lt
• String user (String) session.getAttribute("user
  ")
• out.println(user)
• gt
• lt/H1gt
• lt/bodygt
• lt/htmlgt

25
Java Server Pages and Servlets

• Servlets
• HTML enclosed in Java code
• JSP
• Java code enclosed in HTML
• Easier to Author
• Better tool support

26
How it Works
User Request
Server
FileChanged ?
Create Source
Compile
Execute Servlet
27
Web Application Development Roles

• JSP technology promotes application partitioning
  and separation of tasks
• Java developer builds components encapsulating
  the application logic
• Page designer assembles the application with a
  few method calls

28
Anatomy of a JSP

• Static template text
• Dynamic content
• Directives
• Scripting elements
• Standard actions
• Custom tags

29
Directives

• Gives page information to JSP engine
• Page directive
• lt_at_ page language"java" import"java.sql."
  errorPage"ErrorPage.jsp" gt
• Include directive
• lt_at_ include file"header.htm" gt

30
Creating ListDest.jspDemo
31
Scripting Elements

• Declarations (variables and methods)
• lt! String destination gt
• Scriptlets
• lt destination request.getParameter("destin
  ation")gt
• Expressions
• ltpgtDestination lt destination gt

32
Standard Action Tags

• ltjspforwardgt
• Forwards request to HTML page, JSP, or servlet
• ltjspforward page"relativeUrl" /gt
• ltjspincludegt
• Includes data in a JSP page from another file
• ltjspinclude page"relativeUrl" flush"true" /gt
• ltjspplugingt
• Downloads Java plugin to browser to execute
  applet or bean

33
Standard Action TagsUsing JavaBeans Component

• Locates or instantiates a Bean with a specific
  name and scope
• ltjspuseBean id"cd" class"samples.Cd" /gt
• Sets a property value or values in a Bean
• ltjspsetProperty NAME"cd" PROPERTY"artist"
  VALUE"Sting" /gt
• Gets the value of a Bean property
• artistltjspgetProperty NAME"cd"
  PROPERTY"artist" /gt

34
Using Custom Tags

• Taglib directive
• Defines a custom tag library
• Provides a way to extend JSP's native
  functionality without breaking compatibility
• Syntax
• lt_at_ taglib uri"URIToTagLibrary"
  prefix"tagPrefix" gt

35
Creating Destination.jspDemo
36
JSP Advanced Support in PowerJ 3.6

• HTML and JSP editor with syntax highlighting
• Design time syntax checking
• Automated deployment (WAR file)
• Remote debugging

37
JSP Advanced Support in EA Server 3.6

• Remote debugging
• Access to connection caches
• Configurable threading model
• Access to external parameters
• Inter-server component invocations
• Refresh
• Logging support

38
Summary