Dynamic Web Pages with Servlets and JSP

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

<% Date d=new Date(); String today = DateFormat.getInstance().format(d); %> JSP Example JSP tag <%@ page import=“java.text.*’, java.util.*”%> <html> HTML <head><title><Date Example</title></head> <body> Scriptlet Today is: <em><%=today%></em> </body> </html> Example.jsp • Static: HTML/XML elements • Dynamic: scriptlets • Additional: special JSP elements

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

Dynamic Web Pages with Servlets and JSP