Getting Started With Servlet & JSP | JAVA

3 min readMar 7, 2021

Java Servlets run on server side for web-based application. JAVA have built-in support for multithreading. Servlet API is Standard Java Extension API, (NOT part of core Java) and available as add-on package.

Servlets are protocol and platform independent server side Java components. Clients may range from simple forms to Java Applets. Servlets used as middle tiers for distributed application systems.

Applications & Usages Modes:

Database Connection.
Synchronization (On-line conferencing)
Virtual Server management.
Filters chains of Servers.
HTTP.
CGI replacement.
Server side include.

Security:

Rely on HTTP-specific authentication.
Secure Socket Layer.
Java advantage: no memory access violations, strong typing violations. (Servlet will not crash servers.)
Security Manager. Only trusted servlets will be allow to access network services or local files.
Support fine grained access control (more secure than MS. ActiveX.)

Performance:

Servlet run as light weight thread in process.
CGI run as heavy weight process.

Sample Servlet:

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;public class HelloWorld extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
   response.setContentType(“text/html”);
   PrintWriter out = response.getWriter();
   out.println("<html>");
   out.println("<body>");
   out.println("<head>");
   out.println("<title>Hello World!</title>");
   out.println("</head>");
   out.println("<body>");
   out.println("<h1>Hello World!</h1>");
   out.println("</body>");
   out.println("</html>");
}
}

Java Server Pages Vs Servlets.

Dynamic Page require for:
Working on any web or application server.
Separating the application logic from the appearance of the page.
Allowing fast development and testing.
Simplifying the process of developing interactive web-based applications.
JSP is a new approach to fit this need.
Servlet , to turn page, have to edit and recompile.

Java Servlet Pages Approach.

Separating content generation from presentation.
Emphasizing reusable components.
Simplifying page development with tags.
Java Technology benefits (memory management and security.
Scalability (integrated with J2EE).

JSP Example.

<HTML>
<%@ page language=="java" imports=="com.wombat.JSP.*" %>
<H1>Welcome</H1>
<P>Today is </P>
<jsp:useBean id=="clock" class=="calendar.jspCalendar" />
<UL>
<LI>Day: <%==clock.getDayOfMonth() %>
<LI>Year: <%==clock.getYear() %>
</UL>
<% if (Calendar.getInstance().get(Calendar.AM_PM) ==== Calendar.AM) { %>
Good Morning
<% } else { %>
Good Afternoon
<% } %>
<%@ include file=="copyright.html" %>
</HTML>

JSP Components.

JSP Directives:

<%@ …. %>

JSP Tags:

<jsp:useBean … />
<jsp:setProperty … />
<jsp:getProperty … />
<jsp:include … />
<jsp:forward … />

JSP expression:

<%== … %>

Scripting Elements (scriptlet):

<% … %>

Application Model.

Getting Started With Servlet & JSP | JAVA

Written by Laukikrupne