Spring MVC - Listening to HTTP request as events

In Spring web application, a bean can register RequestHandledEvent to get notifications that an HTTP request has been serviced. This event is published after the request is complete. Let's see how to do that with example.

RequestHandledEvent Example

@Component
public class MyBean {
  
  @EventListener
  public void handleEvent (RequestHandledEvent e) {
      System.out.println("-- RequestHandledEvent --");
      System.out.println(e);
  }
}

@Controller
public class MyWebController {
  
  @RequestMapping("/test")
  @ResponseBody
  public String handle () {
      return "test response from /test";
  }
  
  @RequestMapping("/test2")
  @ResponseBody
  public String handle2 () {
      return "test response from /test2";
  }
}

@SpringBootApplication
public class ExampleMain {
  
  public static void main (String[] args) {
      SpringApplication.run(ExampleMain.class, args);
  }
}

mvn spring-boot:run

Access following URL in your browser:
http://localhost:8080/test
http://localhost:8080/test2

Output on server console:

2017-05-03 19:44:57.296  INFO 13360 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring FrameworkServlet 'dispatcherServlet'
2017-05-03 19:44:57.296  INFO 13360 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization started
2017-05-03 19:44:57.311  INFO 13360 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization completed in 15 ms
-- RequestHandledEvent --
ServletRequestHandledEvent: url=[/test]; client=[0:0:0:0:0:0:0:1]; method=[GET]; servlet=[dispatcherServlet]; session=[null]; user=[null]; time=[25ms]; status=[OK]
-- RequestHandledEvent --
ServletRequestHandledEvent: url=[/test2]; client=[0:0:0:0:0:0:0:1]; method=[GET]; servlet=[dispatcherServlet]; session=[null]; user=[null]; time=[2ms]; status=[OK]

In above output, we see Servlet Request Handled Event, which is a Servlet-specific subclass of RequestHandledEvent. In portlet environment, Spring framework uses another subclass; PortletRequestHandledEvent.

Example Project

Dependencies and Technologies Used:

• Spring Boot 1.5.3.RELEASE
  Corresponding Spring Version 4.3.8.RELEASE
• spring-boot-starter-web : Starter for building web, including RESTful, applications using Spring MVC. Uses Tomcat as the default embedded container.
• JDK 1.8
• Maven 3.3.9