Question

(Page Hit Counter with Cookies) Create a JSP that uses a persistent cookie (i.e., a cookie with an expiration date in the future) to keep track of how many times the client computer has visited the page. Use the setMaxAge method to cause the cookie to remain on the client's computer for one month. Display the number of page hits (i.e., the cookie's value) every time the page loads.

Short answer

Track page hits with a persistent 'pageHitCounter' cookie by updating its value on each visit, setting it to expire in one month.

Step-by-step solution

Import Required Libraries

To start off, you'll need to import the necessary libraries for working with cookies in JSP. These typically include javax.servlet.http.HttpServlet, javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, and javax.servlet.http.Cookie.

Retrieve Existing Cookies

Use HttpServletRequest to fetch all cookies from the client. This can be done using the `request.getCookies()` method. Store them in a Cookie array.

Check for Existing Page Hit Cookie

Iterate through the Cookie array to check if a cookie named 'pageHitCounter' already exists. If it exists, retrieve its current value which represents the number of times the page has been accessed.

Increment Page Hit Counter

If the 'pageHitCounter' cookie is found, convert its value to an integer and increment it by one. If it is not found, set the counter value to one, indicating the first page visit.

Set or Update the Cookie

Create a new cookie or update the existing 'pageHitCounter' cookie with the new counter value. Use `setMaxAge(60*60*24*30)` to ensure the cookie persists for one month, allowing long-term tracking of page visits.

Add Cookie to Response

Add the cookie back to the HttpServletResponse object, using the `response.addCookie(cookie)` method, to ensure it gets sent back to the client's browser.

Display the Page Hit Count

Use `out.println()` within the JSP to display the current number of page hits by accessing the value of the 'pageHitCounter' cookie. Ensure this information is clear and visible to the user.

Key concepts

Java Servlets

Java Servlets are server-side components that handle making web content dynamic. They run on a server that hosts web applications and responds to client requests made over the web.
These servlets are integral to web applications because they can process incoming requests by interacting with the server’s resources, generating responses that can include a wide range of outputs, such as HTML text or data in formats like JSON.
Here are a few key functions:

• Receive requests directly from a client or indirectly through a JSP (JavaServer Page).
• Perform operations such as querying a database or calling an enterprise service.
• Return responses to the client, which can include dynamically generated content.

Java Servlets use the Java programming language, which ensures that web applications are platform-independent. This makes them particularly valuable in networked environments where different servers and devices interact by utilizing the same Java-based applications.

Web Development

Web development encompasses the building and maintenance of websites. It involves a wide range of tasks and technologies, one of which is managing how data is sent and received between clients and servers.
Java is a popular choice in web development because of its versatility and extensive standard library.

• Front-end technologies focus on user-facing aspects like layout and design, usually employing HTML, CSS, and JavaScript.
• Back-end technologies include programming languages like Java, which help in processing requests and managing data.

The server-side of web development is where technologies like JSP and Java Servlets come into play, creating dynamic and interactive applications. This involves using tools and frameworks to ensure the communication between the client and server is smooth and effective.
By using cookies, a key concept in web development, developers can maintain a state across different sessions, improving user experience by personalizing the interaction with the web application.

Persistent Cookies

Persistent cookies outlast the session duration, storing data on the user's computer for a set expiration period. This persistence allows cookies to retain information across multiple sessions.
Unlike session cookies, which are deleted once you close your browser, persistent cookies are designed to remember information over extended periods.

• The expiration date of persistent cookies is set using the `setMaxAge` method, usually defined in seconds.
• They are beneficial for tracking user activity, login details, and preferences over time.

In our JSP page hit counter exercise, the cookie stores the number of times the client has visited the page. By setting it to persist for one month, the server can immediately retrieve returning user's data and calculate their total page hits.
Thus, persistent cookies play an essential role in client-side tracking, enhancing the customization and functionality of web applications by saving user data for future visits.

Client-Side Tracking

Client-side tracking involves collecting data about user interactions directly from their web browser. This kind of tracking is incredibly helpful in understanding user behavior and preferences, often through the use of cookies.
Cookies, especially persistent cookies, enable developers to store small pieces of data directly on the user's machine, allowing the server to remember specific user information across different sessions.

• This data includes user preferences, session details, and website visit counts.
• Client-side tracking maintains privacy by not directly collecting identifiable data without the user's consent.

In web applications, this is often used to enhance the user experience by keeping session persistence and providing customized responses based on previous interactions.
Tools like Java Servlets and JSP use client-side tracking effectively to create dynamic, personalized web interfaces. This technique is vital for metrics, such as page views, which are critical for web analytics and improving the user interface.