How to connect java web front end and back end

In Java Web development, the connection between the front end and the back end is mainly realized in the following ways:

1. HTTP requests and responses : The front end sends data or requests resources to the back end by sending HTTP requests (such as GET, POST, etc.). After receiving the request, the back end processes it, generates an HTTP response, and returns it to the front end. The front end can update the page content by parsing and processing the data returned by the back end.
2. Form submission : The front end submits the data entered by the user to the back end through an HTML form. The back end receives the form data and processes it, which may involve verification, storage, processing and other operations. Servlets or other back-end technologies can be used to process form submission and return the corresponding results to the front end.
3. AJAX Request : The front end sends asynchronous requests to the back end through the AJAX technology in JavaScript to obtain back-end data or perform back-end operations. The back end can provide a special interface to process these AJAX requests and return JSON or other format data to the front end. The front end performs corresponding operations and displays by parsing the data returned by the back end.
4. template engine : The template engine can help to better separate the front end and the back end, so that the front end developers can focus on page design and interaction, while the back end developers are responsible for data processing and logic. Common Java Web template engines include Freemarker, Thymeleaf, etc. They can fill the data passed by the back end into the specified template to generate the final HTML page.
5. WebSocket : If you need to realize real-time communication function, you can use WebSocket technology to establish two-way communication between the front end and the back end. The front-end establishes a WebSocket connection with the back-end through JavaScript code to realize real-time message transmission and data update.

The above methods are common methods of front end and back end contact, which are often used in Java Web development. The specific mode depends on the project requirements and technology stack selection.