Introduction Servlets and JSP

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10 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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Introduction

Servlets and JSP


Celsina Bignoli

bignolic@smccd.net

Dynamic web pages


Content may change based on


identity of the user


user’s browser type


information provided by the user


selections made by the user

CGI


CGI (Common Gateway Inteface)


outlines how a web server communicates with
a program.


Typically written in Pearl (or C)


CGI scripting is
not

efficient


for every request the web server has to create
a new process load an interpreter run the
program and dispose of the process once
done.


CGI improvements


Fast
-
CGI


runs program in a external process or pool of
processes


mod_perl, NSAPI, ISAPI


run server
-
side programs in the same process
as the web server


available only on some web servers

Servlets


Server side Java programs


Solve scalability issue


serlvets are run on threads of execution not separate
processes


Solve portability issue


runs on every platform that supports Java


supported by all most popular web servers


Issue


html tags are embedded in java programs within
out.print() statements


JSP


server
-
side technology


separate dynamic content from static
content of a page


Java scriptlets embedded into html
-
like page


Separate the work of


java programmers


page authors

JSP relationship to Servlets



A JSP is converted into a Servlet

Servlet Example

import java.text.*;

import java.util.*;

import

public class DateServlet extends HttpServlet{


public void doGet(HTTPServletRequest request,


HttpServletResponse response)


throws ServletException, IOException


{


response.setContentType(“text/html’);


PrintWriter out = response.getWriter();


out.println(“<html>”);


out.println(“<head><title><Date Example</title></head>”);


out.println(“<body>”);


out.println(“Today is: “);


Date d = new Date();


out.println(“<em>” + DateFormat.getInstance().format(d)+ “</em>”);


out.println(“<body>”);


out.println(“</html>”);


}

}

embedded HTML

JSP Example


Static: HTML/XML elements


Dynamic: scriptlets


Additional: special JSP elements




Example.jsp

<%@ page import=“java.text.*’, java.util.*”%>

<head><title><Date Example</title></head>

<html>

<%

Date d=new Date();

String today = DateFormat.getInstance().format(d);

%>

Today is:

<em><%=today%></em>

</body>

</html>

HTML

Scriptlet

<body>

JSP tag

JSP alternatives


Active Server Pages


allows you to add VBScript or JScript code to the page


primarily a solution for te Windows platform


PHP


open source web
-
scripting language.


extensive set of predifined functions to access databases, LDAP
directories, mail servers etc…


widely supported


ColdFusion


ColdFusion Markup Language(CFML) accessing databases,
files, mail servers etc…


custom elements can be developed in C++ or Java


JSP Unique Features


JSP is a specification, not a product


competing implementations



integral part of J2EE


access all features of the Java language

How to get Started


Install JDK 5.0


Download Apache Tomcat 5.5 from:

www.apache.org


Use a regular editor or an
IDE that supports JSP

development


Eclipse


JBuilder


JCreator


Oracle JDeveloper


NetBeans


Macromedia DreamWeaver