servelet&jsp

Servelet

&

JSP

Can use web.xml or Annotations to link form action to Servelet

<form method="post" action="Validate">
Name:<input type="text" name="user" /><br/>
Password:<input type="password" name="pass" ><br/>
<input type="submit" value="submit">
</form>

Welcome.java

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class Welcome extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.println("<h2>Welcome user</h2>");
 
    }
}

Validate.java

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class Validate extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
      
            String name = request.getParameter("user");
            String password = request.getParameter("pass");

            if(password.equals("studytonight"))
            {
                RequestDispatcher rd = request.getRequestDispatcher("Welcome");
                rd.forward(request, response);
            }
            else
            {
                out.println("<font color='red'><b>You have entered incorrect password</b></font>");
                RequestDispatcher rd = request.getRequestDispatcher("index.html");
                
            }
  
    }
}




web.xml

<web-app>
    <servlet>
        <servlet-name>Validate</servlet-name>
        <servlet-class>Validate</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>Welcome</servlet-name>
        <servlet-class>Welcome</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Validate</servlet-name>
        <url-pattern>/Validate</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>Welcome</servlet-name>
        <url-pattern>/Welcome</url-pattern>
    </servlet-mapping>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        </welcome-file-list>
</web-app>

JSP

• JSP technology is used to create dynamic web applications. JSP pages are easier to maintain then a Servlet. JSP pages are opposite of Servlets as a servlet adds HTML code inside Java code, while JSP adds Java code inside HTML using JSP tags. Everything a Servlet can do, a JSP page can also do it.

• A JSP page looks similar to an HTML page, but a JSP page also has Java code in it. We can put any regular Java Code in a JSP file using a scriplet tag which start with <% and ends with %>. JSP pages are used to develop dynamic responses.

There are five different types of scripting elements

Scripting Element	Example
Comment	<%-- comment --%>
Directive	<%@ directive %>
Declaration	<%! declarations %>
Scriptlet	<% scriplets %>
Expression	<%= expression %>

                                                                              JSTL

JSP Standard Tag Library(JSTL) is a standard library of readymade tags. The JSTL contains several tags that can remove scriplet code from a JSP page by providing some ready to use, already implemented common functionalities.

• JSTL Core provides several core tags such as if, forEach, import, out etc to support some basic scripting task. Url to include JSTL Core Tag inside JSP page is →

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

For More refer: https://www.studytonight.com/jsp/jstl-in-jsp.php