How can routes be implemented in a web application in Java?

In a Java web application, routes are typically implemented using servlets or frameworks such as Spring MVC or JAX-RS.

Example using annotations in Spring MVC:

@RestController
@RequestMapping("/api")
public class MyController {

    @GetMapping("/users")
    public List<User> getUsers() {
        // logic to get users
    }

    @PostMapping("/users")
    public User createUser(@RequestBody User user) {
        // logic to create a user
    }
}

Here, @RequestMapping and @GetMapping define the routes that will handle HTTP requests.

If using the standard Java EE approach, routes are defined in the deployment descriptor (web.xml) or via @WebServlet annotations:

@WebServlet("/hello")
public class HelloServlet extends HttpServlet {
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        resp.getWriter().write("Hello World");
    }
}

Thus, routes are implemented either declaratively via annotations or through configuration in XML.