Servlets

Servlets are server-side Java programs that handle requests and responses in web applications. Unlike applets, which run in the client’s browser, servlets run on a web server inside a Java container such as Apache Tomcat. They are used to process data, manage sessions, and dynamically generate content for websites and applications.

Servlets form a core part of Java-based web development and provide the foundation for frameworks like JavaServer Pages and Spring MVC.

Advanced

Servlets follow the Java Servlet API, which defines how they receive HTTP requests and return responses. The lifecycle includes initialisation, request handling through the service method, and destruction. Servlets can interact with databases, business logic layers, and other APIs to generate dynamic content.

Advanced setups integrate servlets into enterprise architectures, where they work with filters, listeners, and frameworks to support authentication, routing, and scalability. Performance is enhanced through thread management and connection pooling.

Relevance

• Provides a foundation for Java-based web applications.
• Enables dynamic content generation and complex request handling.
• Supports enterprise-grade applications with scalability and reliability.
• Forms the basis of modern Java web frameworks and platforms.

Applications

• Handling form submissions and processing user data.
• Generating dynamic HTML or JSON content for web apps.
• Managing sessions in e-commerce or SaaS applications.
• Acting as a controller in Java MVC frameworks.

Metrics

• Request response time under varying loads.
• Server throughput and concurrent session handling.
• Memory and CPU usage of the servlet container.
• Error rates during request processing.

Issues

• Requires more configuration compared to lightweight frameworks.
• Scalability challenges if not optimised for concurrency.
• Complex to manage in large applications without frameworks.
• Tight coupling to Java environments limits portability.

Example

An online banking application uses servlets to handle login requests and generate personalised account dashboards. The servlet processes authentication, queries the database, and sends back secure HTML pages to the user.