BAEL-3285 | Simultaneous Spring WebClient calls

spring-5-reactive-client/pom.xml

@@ -77,6 +77,12 @@
             <artifactId>spring-boot-starter-test</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>com.github.tomakehurst</groupId>
+            <artifactId>wiremock</artifactId>
+            <version>2.24.1</version>
+            <scope>test</scope>
+        </dependency>
 
         <dependency>
             <groupId>org.apache.commons</groupId>

spring-5-reactive-client/src/main/java/com/baeldung/reactive/simultaneouswebclient/Client.java

@@ -0,0 +1,66 @@
+package com.baeldung.reactive.simultaneouswebclient;
+
+import org.springframework.web.reactive.function.client.WebClient;
+import reactor.core.publisher.Mono;
+import reactor.core.publisher.Flux;
+import reactor.core.scheduler.Schedulers;
+
+import java.util.List;
+
+public class Client {
+
+    private WebClient webClient;
+
+    public Client(String uri) {
+        this.webClient = WebClient.create(uri);
+    }
+
+    public Mono<User> getUser(int id) {
+        return webClient
+            .get()
+            .uri("/user/{id}", id)
+            .retrieve()
+            .bodyToMono(User.class);
+    }
+
+    public Mono<Item> getItem(int id) {
+        return webClient
+            .get()
+            .uri("/item/{id}", id)
+            .retrieve()
+            .bodyToMono(Item.class);
+    }
+
+    public Mono<User> getOtherUser(int id) {
+        return webClient
+            .get()
+            .uri("/otheruser/{id}", id)
+            .retrieve()
+            .bodyToMono(User.class);
+    }
+
+    public List<User> fetchUsers(List<Integer> userIds) {
+        return Flux.fromIterable(userIds)
+            .parallel()
+            .runOn(Schedulers.elastic())
+            .flatMap(this::getUser)
+            .collectSortedList((u1, u2) -> u2.id() - u1.id())
+          .block();
+    }
+
+    public List<User> fetchUserAndOtherUser(int id) {
+        return Flux.merge(getUser(id), getOtherUser(id))
+            .parallel()
+            .runOn(Schedulers.elastic())
+            .collectSortedList((u1, u2) -> u2.id() - u1.id())
+            .block();
+    }
+
+    public UserWithItem fetchUserAndItem(int userId, int itemId) {
+        Mono<User> user = getUser(userId).subscribeOn(Schedulers.elastic());
+        Mono<Item> item = getItem(itemId).subscribeOn(Schedulers.elastic());
+
+        return Mono.zip(user, item, UserWithItem::new)
+          .block();
+    }
+}

spring-5-reactive-client/src/main/java/com/baeldung/reactive/simultaneouswebclient/Item.java

@@ -0,0 +1,17 @@
+package com.baeldung.reactive.simultaneouswebclient;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+public class Item {
+    private int id;
+
+    @JsonCreator
+    public Item(@JsonProperty("id") int id) {
+        this.id = id;
+    }
+
+    public int id() {
+        return id;
+    }
+}

spring-5-reactive-client/src/main/java/com/baeldung/reactive/simultaneouswebclient/User.java

@@ -0,0 +1,17 @@
+package com.baeldung.reactive.simultaneouswebclient;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+public class User {
+    private int id;
+
+    @JsonCreator
+    public User(@JsonProperty("id") int id) {
+        this.id = id;
+    }
+
+    public int id() {
+        return id;
+    }
+}

spring-5-reactive-client/src/main/java/com/baeldung/reactive/simultaneouswebclient/UserWithItem.java

@@ -0,0 +1,19 @@
+package com.baeldung.reactive.simultaneouswebclient;
+
+public class UserWithItem {
+    private User user;
+    private Item item;
+
+    public UserWithItem(User user, Item item) {
+        this.user = user;
+        this.item = item;
+    }
+
+    public User user() {
+        return user;
+    }
+
+    public Item item() {
+        return item;
+    }
+}

spring-5-reactive-client/src/test/java/com/baeldung/reactive/simultaneouswebclient/ClientIntegrationTest.java

@@ -0,0 +1,71 @@
+package com.baeldung.reactive.simultaneouswebclient;
+
+import org.junit.Test;
+import org.junit.Before;
+import org.junit.After;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+import com.github.tomakehurst.wiremock.WireMockServer;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+import static com.github.tomakehurst.wiremock.core.WireMockConfiguration.wireMockConfig;
+import static com.github.tomakehurst.wiremock.client.WireMock.*;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertEquals;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest
+public class ClientIntegrationTest {
+
+    private WireMockServer wireMockServer;
+
+    @Before
+    public void setup() {
+        wireMockServer = new WireMockServer(wireMockConfig().port(8089));
+        wireMockServer.start();
+        configureFor("localhost", wireMockServer.port());
+    }
+
+    @After
+    public void tearDown() {
+        wireMockServer.stop();
+    }
+
+    @Test
+    public void checkIfCallsAreExecutedSimultaneously() {
+        // Arrange
+        int requestsNumber = 5;
+        int singleRequestTime = 1000;
+
+        for (int i = 1; i <= requestsNumber; i++) {
+            stubFor(
+              get(urlEqualTo("/user/" + i)).willReturn(aResponse()
+                .withFixedDelay(singleRequestTime)
+                .withStatus(200)
+                .withHeader("Content-Type", "application/json")
+                .withBody(String.format("{ \"id\": %d }", i))));
+        }
+
+        List<Integer> userIds = IntStream.rangeClosed(1, requestsNumber)
+          .boxed()
+          .collect(Collectors.toList());
+
+        Client client = new Client("http://localhost:8089");
+
+        // Act
+        long start = System.currentTimeMillis();
+        List<User> users = client.fetchUsers(userIds);
+        long end = System.currentTimeMillis();
+
+        // Assert
+        long totalExecutionTime = end - start;
+
+        assertEquals("Unexpected number of users", requestsNumber, users.size());
+        assertTrue("Execution time is too big", 2 * singleRequestTime > totalExecutionTime);
+    }
+}