Transcript web development

Java web development
Servlet & Java server pages
topics
Setting Up a Servlet and JSP Environment
*Quick history of web development
*CGI
*Java servlet
*Installing the java 2 Standard Edition
1.4 (J2SE 1.4).
*Installing Jakarta Tomcat 5 on Windows
 Java Servlet
 Java server pages.

Setting Up a Servlet and JSP
Environment
Quick history of web development
In the beginning , all the web pages is found in the
server as HTML files , to open any web page the
client send request to the server by sending the web
page name or click on the link for this page, when the
request reach to the server ,this server search about
this file and send the response to the client ,then the
browser show this page at the client.

This is called : RequestResponse ClientServer and
the request and the response is HTML file.
This called : static web pages .
RequestResponse ClientServer
Browser
view the
web page
request
Response
(HTML)
search
HTML file
HTML files
Quick history of web
development
The number of this static pages become
too large and the server can’t keep all
these pages.
 So the users need dynamic pages such as
the search pages , the page contents is
changed for each client , this contents is
come from database which contains new
contents for each client request .

Quick history of web
development
Web server
1
The result
(HTML page)
5
Request to
execute the
program
Show the page
by the browser
2
6
The server call The result
4
the needed
(HTML page)
program
Execute the
program
3
If the program
need database
database
Browser
CGI

The Common Gateway Interface , or CGI, is
commonly referred to as one of the first
practical technologies for creating dynamic
server-side content . with CGI a server passes a
client’s request to an external program. This
program executes, creates some contents, and
sends a response to the client . When first
developed, this functionality available to a web
developer . Needless to say CGI quickly grew in
popularity and become a standard method for
creating dynamic web pages.
CGI is not perfect …….
Each request to a CGI resource creates a new process
on the server and passes information to the process
via standard inputs and environment variables .
The CGI life cycle is very taxing on server resources
and greatly limits the number of concurrent CGI users
a server can support.
It takes a noticeable amount of time to start and stop
the entire process.
Java servlet


In the java world, servlets were designed to solve the problems
of CGI .
Similar to CGI, servlets allow a request to be processed by a
program and let the same program produce a dynamic
response. Servlets additionally defined an efficient life cycle that
include the possibility of using a single process for managing all
requests. This eliminated the multi_process overhead of CGI
and allowed for the mail process to share recourses between
multiple servlets and multiple requests.
Installing the java 2 Standard Edition
1.4 (J2SE 1.4).
J2SE is required to run all java codes, go
to http://java.sun.com/j2se/1.4/
 You can use jcretor or netbeans to
compile and run the programs.

Installing Jakarta Tomcat 5 on Windows
Apache Jakarta is freely available for
download from
http://jakarta.apache.org/tomcat3.
 To download tomcat5.5.17 go to
http://tomacat.apache.org/download55.cgi

Why we need the tomcat ?

The servlet can’t be execute on any computer,
it must execute on a server computer
Installation steps:
1] after download the file, extract
the file on the C drive, change the
file name to tomcat, the path off
the file become :
c:\tomcat
2] right click on my computer
properties advance
Environment Variable
3] in System Variable click on new 
the variable name is JAVA_HOME
and the value is the path of the
JDK in your computer. This path
usually is
C:\Program Files\Java\jdk1.6.0_22
Installation steps:
Copy the file servlet-api.jar found in the path : tomcat\lib
to this path :
C:\Program Files\Java\jdk1.6.0_22\jre\lib\ext
If you don’t copy this file, this common error will appear :
javax.servlet package doesn’t exist
Go to the path :
C:\tomcat\webapps\ROOT\WEB-INF
And create a new folder name it classes :
C:\tomcat\webapps\ROOT\WEB-INF\classes
Now the tomcat is ready, we need
to startup the tomcat
Startup the tomcat.
Go to :
Start-> run -> cmd
 Use the command
cd.. until reach to
the folder :
c:\tomcat\bin
 Write the command
startup this window
will appear:

Open the server from the browser

The port number usually is 8080 you can sure by
search about the port number from the file :
C:\tomcat\conf\sever.xml
Search for this statement
Open the browser then write :
http://localhost:8080/
You can use the shutdown command to shutdown
the tomcat server.
Open the server from the browser
Execute servlet pages

Write the servlet code initially try this code and save it as
NewServlet.java :

Compile the code and but the NewServlet.class file on the path:
C:\tomcat\webapps\ROOT\WEB-INF\classes
Execute servlet pages
Write
http://localhost:8
080/servlet/New
Servlet the
output is :
Use netbeans to install tomcat
and execute the servlet pages :
Servlets…
import javax.servlet.servlet;
interface define the init() method to match
the initilaization phase of servlet life cycle.
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
These two objects represent a client’s
request for dynamic resource and the
Servlet’s response to the client.
import javax.servlet.http.HttpServlet;
doGet and doPost methods
HTML forms and Servlet code
example
Java server pages

JavaServer Pages (JSP) technology enables you to
mix regular, static HTML with dynamically
generated content from servlets.You simply write
the regular HTML in the normal manner, using
familiar Web-page-building tools.You then enclose
the code for the dynamic parts in special tags, most
of which start with <% and end with %>.
Java server pages simple example
JSP
A clear important distinction to make
about JSP is that coding one is nothing
like coding a servlet.
 There are three different types of
scripting elements available for use in jsp:
Scriptlets, expression, and declarations.

JSP Scriptlets
If you want to do something more complex than insert a
simple expression, JSP scriptlets let you insert arbitrary
code into the jsp page. Scriptlets have the following form:
<% Java Code %>
The output.
JSP Expressions
A JSP expression is used to insert values directly
into the output. It has the following form:
<%= Java Expression %>
The expression is evaluated, converted to a string,
and inserted in the page. This evaluation is
performed at run time (when the page is
requested) and thus has full access to information
about the request. For example, the following
shows the date/time that the page was requested:
Current time: <%= new java.util.Date() %>
Deference between expression and
scriptles.
if you want output to appear in the resultant
page, you would use the out variable in the
scriptles, as in the following example.
<%
String queryData = request.getQueryString();
out.println("Attached GET data: " + queryData);
%>
 In this particular instance, you could have
accomplished the same effect more easily by using
the following JSP expression:
Attached GET data: <%= request.getQueryString()
%>

scripltles
expression
The output.
JSP Declarations
A JSP declaration lets you define methods
or fields. A declaration has the following
form:
<%! Java Code %>
Since declarations do not generate any
output, they are normally used in
conjunction with JSP expressions or
scriptlets
declaration