Servlet

Java servlet technology provides Web developers with a simple, consistent mechanism for extending the functionality of a Web server and for accessing existing business systems. Servlets are server-side Java EE components that generate responses to requests from clients. Most of the time, this means generating HTML pages in response to HTTP requests, although there are a number of other standard servlet classes available, for example for WebSocket communication.

The Java servlet API has to some extent been superseded (but still used under the hood) by two standard Java technologies for web services:

1. the Java API for RESTful Web Services (JAX-RS 2.0) useful for AJAX, JSON and REST services, and
2. the Java API for XML Web Services (JAX-WS) useful for SOAP Web Services.

Typical implementations of these APIs on Application Servers or Servlet Containers use a standard servlet for handling all interactions with the HTTP requests and responses that delegate to the web service methods for the actual business logic.