[BAEL-2114] spring-5-reactive & spring-5-mvc | Server Sent Events in Spring (#5146)

* * added spring 5 reactive examples

* * added MVC example
* added spring 5 webflux test

spring-5-mvc/src/main/java/com/baeldung/web/SseEmitterController.java

@@ -1,12 +1,16 @@
 package com.baeldung.web;
 
-import com.baeldung.Constants;
+import java.time.LocalTime;
 import java.util.Date;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter.SseEventBuilder;
+
+import com.baeldung.Constants;
 
 @Controller
 public class SseEmitterController {
@@ -29,4 +33,27 @@ public class SseEmitterController {
         return emitter;
     }
 
+    @GetMapping("/stream-sse-mvc")
+    public SseEmitter streamSseMvc() {
+        SseEmitter emitter = new SseEmitter();
+        ExecutorService sseMvcExecutor = Executors.newSingleThreadExecutor();
+
+        sseMvcExecutor.execute(() -> {
+            try {
+                for (int i = 0; true; i++) {
+                    SseEventBuilder event = SseEmitter.event()
+                        .data("SSE MVC - " + LocalTime.now()
+                            .toString())
+                        .id(String.valueOf(i))
+                        .name("sse event - mvc");
+                    emitter.send(event);
+                    Thread.sleep(1000);
+                }
+            } catch (Exception ex) {
+                emitter.completeWithError(ex);
+            }
+        });
+        return emitter;
+    }
+
 }