BAEL-4915 added in the code for the article on long polling (#10660)

* BAEL-4915 added in the code for the article on long polling using DeferredResult

* BAEL-4915 altered package for long polling article due to previous package being full

Co-authored-by: Liam Garvie <liamgarvie@Liams-MacBook-Pro.local>

spring-web-modules/spring-rest-http-2/src/main/java/com/baeldung/longpolling/client/LongPollingBakeryClient.java

@@ -0,0 +1,42 @@
+package com.baeldung.longpolling.client;
+
+import io.netty.handler.timeout.ReadTimeoutException;
+import org.springframework.boot.web.client.RestTemplateBuilder;
+import org.springframework.stereotype.Component;
+import org.springframework.web.client.ResourceAccessException;
+import org.springframework.web.client.RestTemplate;
+import org.springframework.web.reactive.function.client.WebClient;
+
+import java.time.Duration;
+
+@Component
+public class LongPollingBakeryClient {
+
+    public String callBakeWithRestTemplate(RestTemplateBuilder restTemplateBuilder) {
+        RestTemplate restTemplate = restTemplateBuilder
+          .setConnectTimeout(Duration.ofSeconds(10))
+          .setReadTimeout(Duration.ofSeconds(10))
+          .build();
+
+        try {
+            return restTemplate.getForObject("/api/bake/cookie?bakeTime=1000", String.class);
+        } catch (ResourceAccessException e) {
+            throw e;
+        }
+    }
+
+    public String callBakeWithWebClient() {
+        WebClient webClient = WebClient.create();
+
+        try {
+            return webClient.get()
+              .uri("/api/bake/cookie?bakeTime=1000")
+              .retrieve()
+              .bodyToFlux(String.class)
+              .timeout(Duration.ofSeconds(10))
+              .blockFirst();
+        } catch (ReadTimeoutException e) {
+            throw e;
+        }
+    }
+}

spring-web-modules/spring-rest-http-2/src/main/java/com/baeldung/longpolling/controller/BakeryController.java

@@ -0,0 +1,49 @@
+package com.baeldung.longpolling.controller;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.context.request.async.DeferredResult;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import static java.lang.String.format;
+
+/**
+ * Long polling controller example.
+ */
+@RestController
+@RequestMapping("/api")
+public class BakeryController {
+    private final static Logger LOG = LoggerFactory.getLogger(BakeryController.class);
+    private final static Long LONG_POLLING_TIMEOUT = 5000L;
+
+    private ExecutorService bakers;
+
+    public BakeryController() {
+        bakers = Executors.newFixedThreadPool(5);
+    }
+
+    @GetMapping("/bake/{bakedGood}")
+    public DeferredResult<String> publisher(@PathVariable String bakedGood, @RequestParam Integer bakeTime) {
+
+        DeferredResult<String> output = new DeferredResult<>(LONG_POLLING_TIMEOUT);
+
+        bakers.execute(() -> {
+            try {
+                Thread.sleep(bakeTime);
+                output.setResult(format("Bake for %s complete and order dispatched. Enjoy!", bakedGood));
+            } catch (Exception e) {
+                output.setErrorResult("Something went wrong with your order!");
+            }
+        });
+
+        output.onTimeout(() -> output.setErrorResult("the bakery is not responding in allowed time"));
+        return output;
+    }
+}

spring-web-modules/spring-rest-http-2/src/test/com/baeldung/longpolling/integration/BakeryControllerIntegrationTest.java

@@ -0,0 +1,72 @@
+package com.baeldung.longpolling.integration;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.mock.web.MockAsyncContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.MvcResult;
+import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
+
+import java.io.IOException;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.asyncDispatch;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.request;
+
+@AutoConfigureMockMvc
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+public class BakeryControllerIntegrationTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Test
+    public void givenDeferredResultTimesOut_ThenErrorResponseIsRecieved() throws Exception {
+        MvcResult asyncListener = mockMvc
+          .perform(MockMvcRequestBuilders.get("/api/bake/cookie?bakeTime=6000"))
+          .andExpect(request().asyncStarted())
+          .andReturn();
+
+        enableTimeout(asyncListener);
+
+        String response = mockMvc
+          .perform(asyncDispatch(asyncListener))
+          .andReturn()
+          .getResponse()
+          .getContentAsString();
+
+        assertThat(response)
+          .isEqualTo("the bakery is not responding in allowed time");
+    }
+
+    @Test
+    public void givenDeferredResultSuccessful_ThenSuccessResponseIsRecieved() throws Exception {
+        MvcResult asyncListener = mockMvc
+          .perform(MockMvcRequestBuilders.get("/api/bake/cookie?bakeTime=1000"))
+          .andExpect(request().asyncStarted())
+          .andReturn();
+
+        String response = mockMvc
+          .perform(asyncDispatch(asyncListener))
+          .andReturn()
+          .getResponse()
+          .getContentAsString();
+
+        assertThat(response)
+          .isEqualTo("Bake for cookie complete and order dispatched. Enjoy!");
+    }
+
+    private static void enableTimeout(MvcResult asyncListener) throws IOException {
+        ((MockAsyncContext) asyncListener
+          .getRequest()
+          .getAsyncContext())
+          .getListeners()
+          .get(0)
+          .onTimeout(null);
+    }
+}

spring-web-modules/spring-rest-http/pom.xml

@@ -24,6 +24,10 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-validation</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-webflux</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-oxm</artifactId>