What is Server Sent Event(SSE) and How to Use It in Java Spring Boot?

SSE is a technology for transmitting data from a server to a web client in real-time. It allows the client to establish a persistent connection to the server and receive updates without sending frequent requests. SSE is widely used in applications such as chat apps, stock tickers, and social media feeds. In a Java Spring Boot application, SSE can be implemented using the `javax.servlet.AsyncContext` and the `EventSource` object in JavaScript.