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Servlet Coding Questions


  • Write a Servlet that displays "Hello, World!" on the browser.
java
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public class HelloWorldServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<html><head><title>Hello, World!</title></head>");
        out.println("<body><h1>Hello, World!</h1></body></html>");
    }
}
  • Write a Servlet that accepts a name parameter and displays "Hello, {name}!" on the browser.
java
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public class HelloNameServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        if (name == null || name.isEmpty()) {
            response.sendRedirect("/error");
        } else {
            response.setContentType("text/html");
            PrintWriter out = response.getWriter();
            out.println("<html><head><title>Hello, " + name + "!</title></head>");
            out.println("<body><h1>Hello, " + name + "!</h1></body></html>");
        }
    }
}
  • Write a Servlet that counts the number of times it has been accessed and displays the count on the browser.
java
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public class CountServlet extends HttpServlet {
    private int count = 0;
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        count++;
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<html><head><title>Count</title></head>");
        out.println("<body><h1>Count: " + count + "</h1></body></html>");
    }
}
  • Write a Servlet that reads a text file and displays its contents on the browser.
java
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public class FileServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String filename = request.getParameter("filename");
        if (filename == null || filename.isEmpty()) {
            response.sendRedirect("/error");
        } else {
            BufferedReader reader = new BufferedReader(new FileReader(filename));
            String line;
            response.setContentType("text/html");
            PrintWriter out = response.getWriter();
            out.println("<html><head><title>" + filename + "</title></head>");
            out.println("<body><h1>" + filename + "</h1><pre>");
            while ((line = reader.readLine()) != null) {
                out.println(line);
            }
            out.println("</pre></body></html>");
            reader.close();
        }
    }
}
  • Write a Servlet that accepts a username and password parameter and displays "Welcome, {username}!" on the browser if the username and password are correct, otherwise displays an error message.
java
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public class LoginServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        if (username == null || username.isEmpty() || password == null || password.isEmpty()) {
            response.sendRedirect("/error");
        } else if (username.equals("admin") && password.equals("admin123")) {
            response.setContentType("text/html");
            PrintWriter out = response.getWriter();
            out.println("<html><head><title>Welcome, " + username + "!</title></head>");
            out.println("<body><h1>Welcome, " + username + "!</h1></body></html>");
        } else {
            response.sendRedirect("/error");
        }
    }
}
  • Write a Servlet that displays a list of items and allows the user to add new items to the list.
csharp
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public class ItemListServlet extends HttpServlet {
    private List<String> items = new ArrayList<>();
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<html><head><title>Item List</title></head>");
        out.println("<body><h1>Item List</h1>");
        out.println("<ul>");
        for (String item : items) {
            out.println("<li>" + item + "</li>");
        }
        out.println("</ul>");
        out.println("<form method=\"post\">");
        out.println("Item: <input type=\"text\" name=\"item\">");
        out.println("<input type=\"submit\" value=\"Add\">");
        out.println("</form>");
        out.println("</body></html>");
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String item = request.getParameter("item");
        if (item != null && !item.isEmpty()) {
            items.add(item);
        }
        response.sendRedirect("/itemlist");
    }
}
  • Write a Servlet that allows the user to upload a file and saves it to the server.
java
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public class FileUploadServlet extends HttpServlet {
    private static final String UPLOAD_DIR = "uploads";
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String applicationPath = request.getServletContext().getRealPath("");
        String uploadPath = applicationPath + File.separator + UPLOAD_DIR;
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }
        Part part = request.getPart("file");
        String fileName = part.getSubmittedFileName();
        part.write(uploadPath + File.separator + fileName);
        response.sendRedirect("/fileupload");
    }
}
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