Servlet_JSP

Working of a Servlet

Servlet Lifecycle Methods

ServletContext VS ServletConfig

Servlet Annotations

Annotations can replace equivalent XML configuration in the web deployment descriptor file (web.xml) such as servlet declaration and servlet mapping. Servlet containers will process the annotated classes at deployment time.

package com.example;

import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@WebServlet("/add")
public class AddServlet extends HttpServlet {
    public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException {
        int i = Integer.parseInt(req.getParameter("num1"));
        int j = Integer.parseInt(req.getParameter("num2"));
        int k = i + j;
        Cookie cookie=new Cookie("k",k+"");
        res.addCookie(cookie);
        res.sendRedirect("sq");
    }
}

Why JSP ?

JSP (JavaServer Pages) is used in web development for generating dynamic content by combining HTML and Java code. Key reasons include:

• Separation of Concerns: JSP keeps HTML for presentation and Java for business logic separate, making it easier to maintain.
• Dynamic Content: It generates content dynamically based on backend data or user input.
• Java Integration: Seamlessly works with Java EE technologies like Servlets and JDBC.
• Reusability: Custom tags and tag libraries promote reusable components.
• Session Management: Handles user sessions efficiently.
• Performance: JSP pages are compiled into fast Servlets.
• Platform Independence: JSP is platform-independent, like Java.

How are JSP translated to Servlets

• Servlets are better for logic writing
• JSP is better when some output is to be displayed

Tags in JSP

• <%@ page import="java.util.Date" %> -> Directive tag
• <%! %> -> Declarative tag (section outside of the service method, used for declaring variables)
• <% %> -> Scriplet
• <%= %> -> Expression (for printing)

Builtin Objects in JSP

• request (HttpServletRequest)
• response (HttpServletResponse)
• pageContext (PageContext)
• out (JspWriter) ~ PrintWriter Object
• session (HttpSession)
• application (ServletContext)
• config (ServletConfig)