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Questions.md

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Intermediate Level: Forms, Sessions, and Cookies (26–50)

  1. Create a Servlet that accepts a user’s first and last name and displays a full name.

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

public class FullNameServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String firstName = request.getParameter("firstName");
        String lastName = request.getParameter("lastName");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<p>Full Name: " + firstName + " " + lastName + "</p>");
    }
}

  2. Write a JSP program to store user login information in a session.

    <%
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    if ("admin".equals(username) && "admin123".equals(password)) {
        session.setAttribute("username", username);
        out.println("Login Successful!");
    } else {
        out.println("Invalid Credentials!");
    }
%>

  3. Demonstrate the use of the session implicit object to count the total number of user sessions.

    <%
    Integer sessionCount = (Integer) application.getAttribute("sessionCount");
    if (sessionCount == null) {
        sessionCount = 1;
    } else {
        sessionCount++;
    }
    application.setAttribute("sessionCount", sessionCount);
%>
<p>Total Sessions: <%= sessionCount %></p>

  4. Write a Servlet program to retrieve form data sent via POST method.

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

public class PostServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<p>Hello, " + name + "!</p>");
    }
}

  5. Create a JSP page that uses hidden fields to transfer data between pages.

    <!-- page1.jsp -->
<html>
<body>
    <form action="page2.jsp" method="post">
        <input type="hidden" name="data" value="SecretData">
        <input type="submit" value="Go to Page 2">
    </form>
</body>
</html>

<!-- page2.jsp -->
<%
    String data = request.getParameter("data");
    out.println("Hidden Data: " + data);
%>

  6. Write a JSP program that uses cookies to store a user’s preferred theme (light or dark mode).

    <%
    String theme = request.getParameter("theme");
    if (theme != null) {
        Cookie cookie = new Cookie("theme", theme);
        cookie.setMaxAge(60 * 60 * 24 * 30); // 30 days
        response.addCookie(cookie);
    }
%>
<html>
<body>
    <form action="" method="post">
        <select name="theme">
            <option value="light">Light Mode</option>
            <option value="dark">Dark Mode</option>
        </select>
        <input type="submit" value="Save Theme">
    </form>
</body>
</html>

  7. Create a Servlet that forwards a request to another JSP page using RequestDispatcher.

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

public class ForwardServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        RequestDispatcher dispatcher = request.getRequestDispatcher("forward.jsp");
        dispatcher.forward(request, response);
    }
}

  8. Demonstrate how to use URL rewriting for session tracking in Servlets.

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

public class URLRewriteServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<a href='nextPage.jsp;jsessionid=" + request.getSession().getId() + "'>Next Page</a>");
    }
}

  9. Write a JSP program to validate form data (e.g., name, email) using JavaScript and JSP.

    <html>
<head>
    <script>
        function validateForm() {
            var name = document.forms["myForm"]["name"].value;
            var email = document.forms["myForm"]["email"].value;
            if (name == "" || email == "") {
                alert("Name and Email are required!");
                return false;
            }
        }
    </script>
</head>
<body>
    <form name="myForm" action="validate.jsp" onsubmit="return validateForm()" method="post">
        Name: <input type="text" name="name"><br>
        Email: <input type="text" name="email"><br>
        <input type="submit" value="Submit">
    </form>
</body>
</html>

  10. Create a Servlet that retrieves a list of values sent from an HTML multiple select dropdown.

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

public class MultiSelectServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String[] items = request.getParameterValues("items");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<p>Selected Items:</p>");
        for (String item : items) {
            out.println("<p>" + item + "</p>");
        }
    }
}

  11. Write a JSP program that demonstrates how to upload a file using a form.

    <html>
<body>
    <form action="upload.jsp" method="post" enctype="multipart/form-data">
        <input type="file" name="file">
        <input type="submit" value="Upload">
    </form>
</body>
</html>

    upload.jsp:

    <%
    Part filePart = request.getPart("file");
    String fileName = filePart.getSubmittedFileName();
    filePart.write("C:/uploads/" + fileName);
    out.println("File uploaded successfully!");
%>

  12. Create a Servlet that generates a table of multiplication results for a given number.

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

public class MultiplicationServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int num = Integer.parseInt(request.getParameter("num"));
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<table border='1'>");
        for (int i = 1; i <= 10; i++) {
            out.println("<tr><td>" + num + " x " + i + "</td><td>" + (num * i) + "</td></tr>");
        }
        out.println("</table>");
    }
}

  13. Write a JSP program to display user information stored in a session object.

    <%
    String username = (String) session.getAttribute("username");
    if (username != null) {
        out.println("Welcome, " + username + "!");
    } else {
        out.println("Please log in.");
    }
%>

  14. Create a Servlet that deletes cookies stored in a user's browser.

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

public class DeleteCookieServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie[] cookies = request.getCookies();
        if (cookies != null) {
            for (Cookie cookie : cookies) {
                cookie.setMaxAge(0);
                response.addCookie(cookie);
            }
        }
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<p>Cookies deleted!</p>");
    }
}

  15. Demonstrate how to invalidate a session using the session.invalidate() method in Servlets.

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

public class InvalidateSessionServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        session.invalidate();
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<p>Session invalidated!</p>");
    }
}

  16. Write a JSP program to display a user’s browser and operating system details.

    <%
    String browser = request.getHeader("User-Agent");
    out.println("<p>Browser: " + browser + "</p>");
%>

  17. Create a JSP page that calculates and displays the sum of numbers from 1 to N.

    <%
    int n = 10;
    int sum = 0;
    for (int i = 1; i <= n; i++) {
        sum += i;
    }
%>
<p>Sum of numbers from 1 to <%= n %> is <%= sum %>.</p>

  18. Write a Servlet program that dynamically generates an HTML table with rows and columns.

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

public class TableServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<table border='1'>");
        for (int i = 1; i <= 5; i++) {
            out.println("<tr>");
            for (int j = 1; j <= 5; j++) {
                out.println("<td>" + i + "," + j + "</td>");
            }
            out.println("</tr>");
        }
        out.println("</table>");
    }
}

  19. Create a JSP page to display an error message when a user enters invalid login details.

    <%
    String error = request.getParameter("error");
    if (error != null) {
        out.println("<p style='color:red;'>Invalid login details!</p>");
    }
%>

  20. Write a JSP program to implement a simple user registration form.

    <html>
<body>
    <form action="register.jsp" method="post">
        Name: <input type="text" name="name"><br>
        Email: <input type="text" name="email"><br>
        Password: <input type="password" name="password"><br>
        <input type="submit" value="Register">
    </form>
</body>
</html>