Download Java Server Pages (JSPs)

Enterprise/Server-side Java
Introduction
• Welcome!
• As usual the module lasts for 12 weeks with
the last week being a revision week.
• For assessment details let us refer to the
module web page.
• Module leader is Nic Shulver
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Slide 1
Enterprise/Server-side Java
Our Contact Point
• The course schedule details the subject we will be
teaching each week as well as the practicals.
• Books! - so many to choose from - some quite awful some good.
• A list of books can be found on the Module
Information page.
• You do not have to buy a book - plenty in the library.
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Slide 2
Enterprise/Server-side Java
Other advice
• Please see or email tutors about any aspect of
the module during the 12 weeks.
• If you have a problem understanding some of
the material, then please ask tutors!
• The slides that follow put “server-side Java for
enterprise” in context
• Note emphasis on key words (orange highlight)
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Slide 3
Enterprise/Server-side Java
Java Server Pages
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Format of lecture:
Introduction
What are Java Server Pages? (JSPs)
What do you need to run JSPs?
Demo of an example of a JSP in action
Tutorial work will get you going straight away
on understanding the architecture and running
your first JSP
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Slide 4
Enterprise/Server-side Java
Overview/history - 90’s
• Early web users were limited to static HTML.
• Useful for presenting company information often in a
hierarchical manner.
• Little or no interaction with the user.
• Java applets addressed this problem enabling
additional code to be downloaded but still a problem
of building customised information.
• Dynamically generated HTML using the Common
Gateway Interface (CGI) was also a proposed
solution.
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Slide 5
Enterprise/Server-side Java
Year 2000 onwards
• CGI and generated HTML was the forerunner
for server-side Java based techniques.
• Java Servlets.
• JavaServer Pages (JSP).
• Component-based computing (Enterprise
JavaBeans).
• Active Server Pages (ASP, ASP.net).
• Personal Hypertext Preprocessor (PHP)
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Slide 6
Enterprise/Server-side Java
Evolution of Applications
• One-tier - mainframe based/dumb terminal/central
application source.
• Also modern standalone/PC/Mini computers/multi
copy of application.
• What we might think of as a simple, “normal”
application.
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Slide 7
Enterprise/Server-side Java
Evolution of Applications
• Two tier - client-server - distributed part of the
application on the client (GUI) and part on the
server.
• Early versions of client-server required
installation of GUI and business logic.
• Recently, Java applets downloadable on
demand.
• With server-side servlets and JSP, no
download and the browser is used as the
interface - this is a good solution!
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Slide 8
Enterprise/Server-side Java
Evolution of Applications
• Three tier/n-tier - user interface(UI) layer; the
business layer(BL) and the database
layer(DL)
• UI - presentation of information, browsers such as
Firefox or Internet Explorer on the client
• BL - logic of procedures about the business, best
done on a server [why?]
• DL - where the data is stored - usually a relational
database but could be an object oriented database
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Slide 9
Enterprise/Server-side Java
Benefits of Web-Enabled
n-tier Applications
• Web applications enable ‘things’ to be done from a web browser
- e.g. online banking.
• Run from anywhere – no installation fee, may incur network
communication costs of course.
• Cost reduction:
• Browser based interface is easy to use - little training
required.
• Development costs lower as using a standard interface.
• No permanent installation on the user’s machine.
• Use of open standards:
• Maintenance easier.
• Enhancement of applications easier.
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Slide 10
Enterprise/Server-side Java
Web Enabling Techniques
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How to develop web-based applications?
How can a server process multiple requests?
Need a fast response!
Scalability - HTTP protocol - works in a
stateless request-response mode - means it
does not bind a server to a client for an
inordinate amount of time.
• Some techniques which can be used to
concurrently satisfy thousands of requests.
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Slide 11
Enterprise/Server-side Java
Stuff that we need
• We are going to spend the next four weeks looking at Java
Server Pages (JSPs).
• Just like when using ASP or PHP, we need a server that
understands our JSP code.
• We need an HTTP server which supports JSP.
• We will use server software called “Tomcat”
• Tomcat is running on one of our servers: fcet11
• You can also download Tomcat for home use and run a server on
your home PC
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Slide 12
Enterprise/Server-side Java
What are JSPs?
• They are HTML documents that are interleaved with
Java which provides the dynamic content.
• JSPs are server-side - they accept a request and
generate a response (an HTML document).
• JSP is the next generation on from Servlets - an
extension of Servlets with more power and flexibility.
• JSP is the equivalent of Microsoft’s Active Server
Pages (ASP) technology and Zend's PHP
environment.
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Slide 13
Enterprise/Server-side Java
JSPs… Servlets… ???
• JSPs are an extension of Java Servlet
technology.
• JSPs automatically generate Servlets which
are Java class files run on the server.
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It is possible to code your own Servlets and
include them in with your JSP web application.
A useful source of information for JSPs and
Servlet technologies is the Java Server Pages
homepage at Sun:
http://java.sun.com/products/jsp/index.html
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Slide 14
Enterprise/Server-side Java
Facts about JSPs
• All JSPs have a file extension of .jsp
• JSP is meant to be easier than Servlets.
• Syntax of a typical JSP is on the next two
slides.
• Over the next four weeks we will look at the
syntax of JSPs in depth.
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Slide 15
simpleguestlist.jsp
<html>
<head>
<title>An Example of a Simple JSP Accessing a database Model</title>
</head>
<body>
<div align="center">
A Listing Of Guests
</div>
<br><br>
<%@ page import="java.sql.*" %>
<table width="100%" border="2" bgcolor="silver">
<tr><th width="50%">Email</th>
<th width="25%">Firstname</th>
<th width="25%">Lastname</th>
</tr>
<%
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance();
Connection conn = DriverManager.getConnection("jdbc:odbc:GuestBook");
Statement statement = conn.createStatement();
String sql = "SELECT * FROM GuestBook";
ResultSet rs = statement.executeQuery(sql);
while (rs.next())
{
%>
<tr>
<td><%= rs.getString("Email") %></td>
<td><%= rs.getString("FirstName") %></td>
<td><%= rs.getString("LastName") %></td>
</tr>
<%
}
%>
</table>
<%
if (statement != null)
statement.close();
if (conn != null)
conn.close();
}
catch (Exception e) {out.print(e);}
%>
</body>
</html>
Enterprise/Server-side Java
Kit required
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What do you need to develop and run JSPs?
JDK (Java Development Kit and runtime)
Tomcat HTTP server
With database interaction we need a database
– we will use Access for convenience but
MySQL is also of interest
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Slide 18
Enterprise/Server-side Java
Demo of a JSP
• This example is a JSP which uses a DSN-less
connection to the GuestBook database
• The application model is essentially a JSP
connecting to a database
• It renders dynamically to the user’s browser
the contents of a table
• As the table changes the content of the page will
reflect this change – hence it dynamic – built at
each request
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Slide 19
Enterprise/Server-side Java
Example
http://fcet11.staffs.ac.uk:8080/nas1/examples/SimpleGuestList.jsp
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Slide 20
Enterprise/Server-side Java
JSP Translation process
Browser Tier
Browser
Server Tier
HTTP Server
TOMCAT
Database
Tier
Query for data content
Request: JSP translated
into a Servlet .java file and then
compiled into a Servlet class
.jsp file
(HTML interleaved
with Java)
Backend database usually on
a separate database server
Request:Browser page
link to call .jsp(either
via locator or a link on an
HTML input page
Response: HTML for output sent from Server
Response
HTML document
Enterprise/Server-side Java
Result Returned
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Slide 22
Enterprise/Server-side Java
Summary
• We have established that JSP represents a
technology that can be used for dynamic web
applications
• The market for this type of technology is well
established (J2EE market)
• JSP demands some programming skills but is
more and more seen as an integration
technology with can dovetail with technologies
such as XML
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Slide 23
Enterprise/Server-side Java
Summary
• We used an HTTP server which supports JSP
• If you were choosing an ISP and wished to run JSP then you
would need to check that they support JSP
• We highlighted the features of a JSP
• A .jsp file is essentially HTML with Java code inserts
• When the .jsp file is called via a browser a .java file is created
to represent Servlet source code and then the .java file is
compiled into a bytecode file with a .class extension.
• The compilation is only done once - subsequent calls to the
JSP use the already compiled .class file
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Slide 24