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Alternatives to JSP (view/templating layer):

• Thymeleaf — most common modern replacement, natural HTML templating, integrates cleanly with Spring Boot
• FreeMarker — template engine, still used in some legacy/enterprise apps
• Mustache — logic-less templates, lightweight
• React / Angular / Vue — the real modern default; backend just returns JSON (REST API), frontend handles all rendering client-side. Most new apps go this route now instead of server-side templating.

Servlets are the core of Java web development: a Java class that handles HTTP requests while the container (Tomcat, Jetty) manages the low-level plumbing. I'd use them directly for filters, file handling, or tiny services. Otherwise Spring MVC's DispatcherServlet already sits on top of them, so understanding servlets mainly helps with debugging.

JSP lets you write HTML with embedded Java instead of printing HTML from servlets. It suits server-rendered pages and older enterprise apps, but it's mostly legacy now. Thymeleaf or FreeMarker are better choices today.

REST is an architectural style (not a technology) that exposes resources over HTTP, usually as JSON, and stays stateless. It's the right fit when the frontend is separate (React, Angular, mobile) or when microservices need to talk to each other. It's easy to scale and works with any client.

Alternatives:

• Instead of servlets/JSP: Spring Boot, plus Thymeleaf or a JavaScript frontend.
• Instead of REST: GraphQL for flexible client queries, gRPC for fast internal service calls, WebSockets/SSE for real-time features, and Kafka/RabbitMQ for async communication.
• Other stacks: Node.js, Django/FastAPI, Go.

Why banks use Java + servlets for netbanking:

1. Mature & stable — 25+ years battle-tested, low-risk for financial systems
2. Strong transactions — JTA/JDBC handle ACID transactions well (critical for fund transfers)
3. Security ecosystem — Spring Security, JAAS, long track record trusted by regulators
4. Compliance-friendly — built-in audit logging, session/access control aligns with PCI-DSS/RBI norms
5. Legacy integration — core banking systems (COBOL/Java/mainframes) integrate easily via Java
6. Fits the use case — netbanking is mostly request-response, not high-concurrency streaming, so blocking servlet model works fine
7. Talent pool — huge, stable Java/Spring developer base
8. Enterprise vendor support — WebLogic/WebSphere/JBoss are built around servlets

Caveat: newer fintechs/neobanks use reactive stacks (WebFlux, Node.js, Go) for high-scale real-time needs — but traditional banks stick with servlets for stability + compliance, not raw performance.

No. Servlets are the traditional foundation (Spring MVC, JAX-RS/Jersey, Struts all run inside a servlet container like Tomcat, using blocking thread-per-request).

But reactive/non-blocking frameworks skip servlets entirely, running on Netty instead: Spring WebFlux, Vert.x, Micronaut (Netty mode), Quarkus (reactive), Play. These use event-loop I/O for better concurrency at scale.

Servlet-based = traditional blocking stack. Non-servlet = reactive stack (Netty-based), used when you need high concurrency without a thread per request.

Servlet = low-level Java mechanism that handles raw HTTP requests/responses (doGet, doPost, etc.) — general purpose, can output anything (HTML, JSON, etc.), can maintain session state.

RESTful web service = an architectural style for designing resource-based APIs — uses HTTP verbs (GET/POST/PUT/DELETE) mapped to CRUD, typically returns JSON, and should be stateless.

Nutshell :
Servlet = how requests are received;
REST = how your API should be designed/structured.