Web Component - Servlet Overview
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Which of the following describes a servlet?

  • An application that only serves static content.
  • A database management system.
  • A client-side script that runs in the browser.
  • A Java program that runs on a web server. (correct)

    • Servlets are designed exclusively for the HTTP protocol.

    False

    Name one advantage of using servlets in web applications.

    Dynamic content generation

    The service method of a servlet is invoked after the __________ method.

    <p>init</p> Signup and view all the answers

    Match the following servlet lifecycle stages with their descriptions:

    <p>Loading = The servlet class is loaded into memory. Instantiation = An instance of the servlet is created. Initialization = The init method is called. Service = The service method handles client requests. Destruction = The destroy method is called before removal from memory.</p> Signup and view all the answers

    What method should be called to retrieve a single value of a request parameter?

    <p>getParameter()</p> Signup and view all the answers

    The deployment descriptor (web.xml) is always required when using servlet annotations.

    <p>False</p> Signup and view all the answers

    What type of data structure does getParameterValues() return?

    <p>An array of String objects</p> Signup and view all the answers

    The method _____ returns null if the specified request parameter does not exist.

    <p>getParameter</p> Signup and view all the answers

    Match the following methods with their descriptions:

    <p>getParameter() = Gets the single value of a request parameter getParameterValues() = Gets multiple values of a request parameter setParameter() = Sets the value of a request parameter removeParameter() = Removes a request parameter from the request object</p> Signup and view all the answers

    When would you use the getParameterValues() method?

    <p>When the parameter may have multiple values</p> Signup and view all the answers

    Servlet API 3.0 introduced a new package for annotating servlet classes.

    <p>True</p> Signup and view all the answers

    What is the purpose of request parameters in a servlet?

    <p>To provide extra information needed to handle requests</p> Signup and view all the answers

    Which method is used to submit processed data to a specified resource?

    <p>POST</p> Signup and view all the answers

    GET requests can send a large amount of data.

    <p>False</p> Signup and view all the answers

    Name one key difference between GET and POST requests.

    <p>GET requests are idempotent, while POST requests are non-idempotent.</p> Signup and view all the answers

    The two main packages that group servlet API classes are javax.___ and javax.servlet.___.

    <p>servlet, http</p> Signup and view all the answers

    Match the following request methods with their characteristics:

    <p>GET = Can be bookmarked POST = Cannot be bookmarked</p> Signup and view all the answers

    What is the role of the 'service' method in a servlet?

    <p>Provides response for incoming requests</p> Signup and view all the answers

    POST requests are considered more secure than GET requests.

    <p>True</p> Signup and view all the answers

    What is Tomcat in relation to web servers?

    <p>Tomcat is a combination of a Web Server and a Servlet Server.</p> Signup and view all the answers

    Which of the following methods can be used for session tracking?

    <p>Using hidden values</p> Signup and view all the answers

    Cookies are large files stored on the server for session tracking.

    <p>False</p> Signup and view all the answers

    What method is used to retrieve hidden values sent back to a servlet?

    <p>getParameter</p> Signup and view all the answers

    Session tracking technique that involves adding a parameter at the end of the URL is known as __________.

    <p>URL Rewriting</p> Signup and view all the answers

    What happens to cookies after their expiration date?

    <p>They are no longer sent to the server</p> Signup and view all the answers

    Match the session tracking methods with their descriptions:

    <p>Hidden Values = Included in HTML forms to track data Cookies = Small text files storing name=value pairs URL Rewriting = Appends data as a parameter to the URL Session Tracking Tools = Utilizes servlet API for managing sessions</p> Signup and view all the answers

    What is the primary purpose of session tracking in web applications?

    <p>To maintain state and track user data across requests</p> Signup and view all the answers

    The hidden values in a form are submitted to the servlet using the __________ method after confirmation.

    <p>POST</p> Signup and view all the answers

    What is the first step in creating a servlet?

    <p>Create a project</p> Signup and view all the answers

    HTTP is a stateful protocol that retains client-server interactions.

    <p>False</p> Signup and view all the answers

    What is the purpose of the deployment descriptor?

    <p>It provides the web container with information about the servlet to be invoked.</p> Signup and view all the answers

    A session can be defined as a series of related interactions between a single client and the web server over a period of __________.

    <p>time</p> Signup and view all the answers

    Match the servlet components with their descriptions:

    <p>WebApplication = Represents the whole application Servlet = A sub-element that represents the servlet ServletName = A sub-element that represents the name of the servlet ServletClass = A sub-element that represents the class of the servlet</p> Signup and view all the answers

    Which method must be implemented when creating a servlet that extends HttpServlet?

    <p>doGet()</p> Signup and view all the answers

    The server can associate different requests from the same client together using HTTP.

    <p>False</p> Signup and view all the answers

    What is a common URL mapping pattern used to invoke a servlet?

    <p>A specific URL path defined in the deployment descriptor.</p> Signup and view all the answers

    What does the getParameter() method do in the servlet API?

    <p>Fetches parameter values at the server side</p> Signup and view all the answers

    Data stored in session tracking using the Servlet API is kept on the client side.

    <p>False</p> Signup and view all the answers

    What method do you use to create a new session in the HttpServletRequest interface?

    <p>getSession</p> Signup and view all the answers

    The Web Container generates a unique session __________ for tracking client requests.

    <p>ID</p> Signup and view all the answers

    Match the HttpSession method with its description:

    <p>getSession() = Returns the current session or creates a new session if none exists. getSession(boolean create) = Returns the current session; creates a new one only if 'create' is true. setAttribute(String name, Object value) = Stores data in the session using a name/value pair. invalidate() = Ends the session and clears the session data from the server.</p> Signup and view all the answers

    What issue do cookies and hidden data face in session tracking?

    <p>They are not secured and challenging for large data sets.</p> Signup and view all the answers

    The client must send back the session ID with each request to maintain a session.

    <p>True</p> Signup and view all the answers

    What is one method of the HttpSession class used to manipulate session data?

    <p>setAttribute</p> Signup and view all the answers

    Study Notes

    Web Component - Servlet

    • A web application is an application accessible via the web
    • It is composed of web components (e.g., Servlet, JSP) and other elements (e.g., HTML, CSS, JavaScript)
    • Web components execute in a web server and respond to HTTP requests

    Servlets

    • Servlet technology is primarily designed for use with the HTTP protocol of the web
    • Servlets are Java programs running on a web server
    • Java servlets process client requests or produce dynamic web pages
    • Servlets act as a middle layer between web browser requests and a database
    • Units of Java code that run on a server-side
    • Run in containers
    • Help with client-server communications
    • Can run over HTTP (though not necessarily)

    Servlet API

    • Provides interfaces and classes for supporting servlets
    • These interfaces and classes are grouped into two packages: javax.servlet and javax.servlet.http

    The Servlet Interface

    • init(ServletConfig config): Initializes the servlet (this method is invoked once by the web container)
    • service(ServletRequest request, ServletResponse response): Provides a response to the incoming request (invoked with each request by the web container)
    • destroy(): Invoked once and indicates the servlet is being destroyed
    • getServletConfig(): Returns the ServletConfig object
    • getServletInfo(): Returns information about the servlet (e.g., writer, copyright, version)

    Servlet Lifecycle

    • Servlet class is loaded
    • Servlet instance is created
    • init method is invoked
    • service method is invoked
    • destroy method is invoked

    Anatomy of GET Request

    • The query string (name/value pairs) is sent inside the URL
    • Data is sent in the request header

    Anatomy of POST Request

    • The query string (name/value pairs) is sent in the HTTP message body
    • Original data is sent in the message body

    GET vs POST Requests

    • GET: limited data, data in URL, not secured, can be bookmarked, idempotent
    • POST: large data, data in body, secured, cannot be bookmarked, not idempotent

    Servlet Architecture Overview

    • Parameters, protocol, remote host, ServerInputStream(binary data etc.)
    • doGet(ServletRequest req, ServletResponse res)
    • doPost(ServletRequest req, ServletResponse res)
    • Mime type for reply, reply data. ServletOutputStream

    The HttpServlet Class

    • Defines a servlet for the HTTP protocol
    • Extends GenericServlet and implements service method
    • service method acts as a dispatcher for HTTP requests.

    The HttpServletRequest Interface

    • doXxx method argument of HttpServletRequest type
    • Contains HTTP request information (parameter name and values, attributes, input stream)
    • Sub-interface of ServletRequest for all kinds of clients

    The HttpServletResponse Interface

    • doXxx method argument of HttpServletResponse type
    • Assists a servlet in sending a response to the client
    • Sub-interface of ServletResponse, providing a more general interface

    Request Parameters

    • Servlets can receive multiple request parameters (name/value pairs)
    • Parameters are typically in the query string or post data
    • getParameter() retrieves a single parameter value
    • getParameterValues() returns multiple values (e.g., for checkboxes).

    Servlet Annotation

    • Replacement for web.xml deployment descriptor
    • Uses @WebServlet to declare a servlet
    • Processed by servlet containers at deployment time

    Steps to Create a Servlet

    1. Create a project
    2. Create a Servlet
    3. Configure the Deployment Descriptor
    4. Run the Project
    5. Access the Servlet

    Session Tracking

    • Web servers use HTTP (stateless protocol), losing connection between browser and server after a transaction.

    • Session tracking allows tracking of related client requests.

    • Techniques:

      • Hidden values
      • Cookies
      • URL Rewriting
      • Servlet API (HttpSession)

    HttpSession

    • Using HttpSession in servlets gives more secure and organized session tracking.
    • Create a new session using request.getSession(true)
    • Obtain a pre-existing session using request.getSession(false)
    • Destroy a session using session.invalidate()

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    Chapter 3 Web Component - Servlet PDF

    Description

    This quiz covers the fundamental concepts of web components, specifically focusing on Java Servlets. You'll learn about their functions, architecture, and the Servlet API, which supports servlet development. Test your understanding of how servlets interact with web browsers and databases.

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