11. WEB APPLICATION DEVELOPMENT Part-2 By LN RAO | 05-NOV-24 | Ashok IT

Overview

This class introduces Java web application development as the next Advanced Java topic after JDBC. The instructor distinguishes it from:

• Core Java, typically used to build standalone applications with a main method.
• Advanced Java, which covers web applications.
• Full-stack and distributed development, which build on web application concepts.

The lesson explains how a web server, server-side Java code, and a database work together to support interactive websites.

Web Servers and Website Types

A browser acts as an HTTP client: it sends requests to a web server, which returns responses. The instructor describes two broad types of websites:

• Static websites serve fixed resources, such as HTML, CSS, and images.
• Dynamic websites accept user input and return user-specific responses, such as an account balance.

In the instructor’s model, a web server has two main functional parts:

1. A networking module, which manages connections and communication with browsers.
2. An I/O module, which reads web resources from disk and serves them.

A web server can serve static content on its own. The lesson explains that it cannot independently support dynamic applications because it cannot communicate with a database, process application data, or generate a data-dependent response page.

Server-Side Programs

A server-side program extends what a web server can do. The two Java technologies introduced are:

• Servlets
• JSP (JavaServer Pages), which the instructor explains is converted internally into Java code

The instructor describes servlets and JSP as web components and dynamic web resources. Static files are still needed, but dynamic resources enable user interaction and make a site dynamic.

For a balance inquiry, the server-side program’s work is outlined as follows:

1. Obtain the user’s input from the web server.
2. Use JDBC to communicate with the database and submit the appropriate query or update.
3. Process the returned data.
4. Produce an HTML response page.
5. Hand the page back to the web server, which returns it to the browser.

The web server remains responsible for communicating with the browser; the server-side program handles application logic and database work.

Web Containers and Tomcat

A web container is described as server software containing three modules:

• Web server
• Servlet container
• JSP container

The web server handles communication and file delivery, while the servlet and JSP containers execute their corresponding server-side components. The instructor says that Java web applications generally need these execution components in addition to a web server.

The course will use Apache Tomcat to run applications. The instructor characterizes Tomcat as a web container, not a full application server, and says it does not support EJBs. In the Q&A, he contrasts Tomcat with application servers such as IBM WebSphere and JBoss, which he says provide additional capabilities.

As a simplified distinction, the instructor presents:

Application server = web container + EJB container

Web Applications and Technologies

A web application is a computer application that provides services to users through the web. The instructor also refers to it as an online application, an internet-based application, or a dynamic website.

Examples include online banking, reservations, shopping, and insurance services.

The Java technologies identified for a Java web application are:

1. Servlets
2. JSP
3. JDBC

Upcoming classes will focus particularly on servlets and JSP, while JDBC is used for database access.

Review, Guidance, and Q&A

The instructor reviews the distinction between static and dynamic websites and the browser–web server request/response model. Students are advised to take notes and regularly review previous material.

The instructor says the next class will begin the servlet topic and will later demonstrate installing Tomcat. The closing Q&A clarifies that:

• Server-side Java code accesses databases using JDBC.
• Apache HTTP Server alone is not enough to run a Java web application.
• Tomcat differs from application servers that provide broader services.
• EJB is described as largely obsolete in current practice, though application servers still offer other services.

Main Speakers and Source

• LN Rao: Instructor and primary speaker; presents the lesson and answers student questions.
• Students: Ask questions during the closing Q&A.
• Source: A Java web application development class from Ashok IT, published on the “JAVA is Evergreen” channel.