BAEL-6911 A Guide to RestClient in Spring Boot (#14893)

spring-boot-modules/spring-boot-3/pom.xml

@@ -41,6 +41,27 @@
             <artifactId>mockserver-netty</artifactId>
             <version>${mockserver.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${jupiter.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <version>${jupiter.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <version>${jupiter.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <version>${jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.mock-server</groupId>
             <artifactId>mockserver-client-java</artifactId>
@@ -187,8 +208,46 @@
         <maven-surefire-plugin.version>3.0.0-M7</maven-surefire-plugin.version>
         <start-class>com.baeldung.sample.TodoApplication</start-class>
         <mockserver.version>5.14.0</mockserver.version>
-        <spring-boot.version>3.1.0</spring-boot.version>
+        <spring-boot.version>3.2.0-SNAPSHOT</spring-boot.version>
         <lombok-mapstruct-binding.version>0.2.0</lombok-mapstruct-binding.version>
+        <jupiter.version>5.10.0</jupiter.version>
     </properties>
 
+    <repositories>
+        <repository>
+            <id>spring-milestones</id>
+            <name>Spring Milestones</name>
+            <url>https://repo.spring.io/milestone</url>
+            <snapshots>
+                <enabled>false</enabled>
+            </snapshots>
+        </repository>
+        <repository>
+            <id>spring-snapshots</id>
+            <name>Spring Snapshots</name>
+            <url>https://repo.spring.io/snapshot</url>
+            <releases>
+                <enabled>false</enabled>
+            </releases>
+        </repository>
+    </repositories>
+    <pluginRepositories>
+        <pluginRepository>
+            <id>spring-milestones</id>
+            <name>Spring Milestones</name>
+            <url>https://repo.spring.io/milestone</url>
+            <snapshots>
+                <enabled>false</enabled>
+            </snapshots>
+        </pluginRepository>
+        <pluginRepository>
+            <id>spring-snapshots</id>
+            <name>Spring Snapshots</name>
+            <url>https://repo.spring.io/snapshot</url>
+            <releases>
+                <enabled>false</enabled>
+            </releases>
+        </pluginRepository>
+    </pluginRepositories>
+
 </project>

spring-boot-modules/spring-boot-3/src/main/java/com/baeldung/restclient/Article.java

@@ -0,0 +1,34 @@
+package com.baeldung.restclient;
+
+import java.util.Objects;
+
+public class Article {
+    Integer id;
+    String title;
+
+    public Article(Integer id, String title) {
+        this.id = id;
+        this.title = title;
+    }
+
+    public Integer getId() {
+        return id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Article article = (Article) o;
+        return Objects.equals(id, article.id) && Objects.equals(title, article.title);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id, title);
+    }
+}

spring-boot-modules/spring-boot-3/src/main/java/com/baeldung/restclient/ArticleController.java

@@ -0,0 +1,45 @@
+package com.baeldung.restclient;
+
+import org.springframework.web.bind.annotation.*;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+
+@RestController
+@RequestMapping("/articles")
+public class ArticleController {
+    Map<Integer, Article> database = new HashMap<>();
+
+    @GetMapping
+    public Collection<Article> getArticles() {
+        return database.values();
+    }
+
+    @GetMapping("/{id}")
+    public Article getArticle(@PathVariable Integer id) {
+        return database.get(id);
+    }
+
+    @PostMapping
+    public void createArticle(@RequestBody Article article) {
+        database.put(article.getId(), article);
+    }
+
+    @PutMapping("/{id}")
+    public void updateArticle(@PathVariable Integer id, @RequestBody Article article) {
+        assert Objects.equals(id, article.getId());
+        database.remove(id);
+        database.put(id, article);
+    }
+
+    @DeleteMapping("/{id}")
+    public void deleteArticle(@PathVariable Integer id) {
+        database.remove(id);
+    }
+    @DeleteMapping()
+    public void deleteArticles() {
+        database.clear();
+    }
+}

spring-boot-modules/spring-boot-3/src/main/java/com/baeldung/restclient/RestClientApplication.java

@@ -0,0 +1,13 @@
+package com.baeldung.restclient;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class RestClientApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(RestClientApplication.class, args);
+    }
+
+}

spring-boot-modules/spring-boot-3/src/test/java/com/baeldung/restclient/RestClientIntegrationTest.java

@@ -0,0 +1,114 @@
+package com.baeldung.restclient;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.web.server.LocalServerPort;
+import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.http.MediaType;
+import org.springframework.web.client.RestClient;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+public class RestClientIntegrationTest {
+
+	@LocalServerPort
+	private int port;
+	private String uriBase;
+	RestClient restClient = RestClient.create();
+
+	@BeforeAll
+	public void setup() {
+		uriBase = "http://localhost:" + port;
+	}
+
+	@AfterEach
+	public void teardown() {
+		restClient.delete()
+				.uri(uriBase + "/articles")
+				.retrieve()
+				.toBodilessEntity();
+	}
+
+	@Test
+	void shouldGetArticlesAndReturnString() {
+		String articlesAsString = restClient.get()
+				.uri(uriBase + "/articles")
+				.retrieve()
+				.body(String.class);
+
+		assertThat(articlesAsString).isEqualTo("[]");
+	}
+
+	@Test
+	void shouldPostAndGetArticles() {
+		Article article = new Article(1, "How to use RestClient");
+		restClient.post()
+				.uri(uriBase + "/articles")
+				.contentType(MediaType.APPLICATION_JSON)
+				.body(article)
+				.retrieve()
+				.toBodilessEntity();
+
+		List<Article> articles = restClient.get()
+				.uri(uriBase + "/articles")
+				.retrieve()
+				.body(new ParameterizedTypeReference<>() {});
+
+		assertThat(articles).isEqualTo(List.of(article));
+	}
+
+	@Test
+	void shouldPostAndPutAndGetArticles() {
+		Article article = new Article(1, "How to use RestClient");
+		restClient.post()
+				.uri(uriBase + "/articles")
+				.contentType(MediaType.APPLICATION_JSON)
+				.body(article)
+				.retrieve()
+				.toBodilessEntity();
+
+		Article articleChanged = new Article(1, "How to use RestClient even better");
+		restClient.put()
+				.uri(uriBase + "/articles/1")
+				.contentType(MediaType.APPLICATION_JSON)
+				.body(articleChanged)
+				.retrieve()
+				.toBodilessEntity();
+
+		List<Article> articles = restClient.get()
+				.uri(uriBase + "/articles")
+				.retrieve()
+				.body(new ParameterizedTypeReference<>() {});
+
+		assertThat(articles).isEqualTo(List.of(articleChanged));
+	}
+
+	@Test
+	void shouldPostAndDeleteArticles() {
+		Article article = new Article(1, "How to use RestClient");
+		restClient.post()
+				.uri(uriBase + "/articles")
+				.contentType(MediaType.APPLICATION_JSON)
+				.body(article)
+				.retrieve()
+				.toBodilessEntity();
+
+		restClient.delete()
+				.uri(uriBase + "/articles")
+				.retrieve()
+				.toBodilessEntity();
+
+		List<Article> articles = restClient.get()
+				.uri(uriBase + "/articles")
+				.retrieve()
+				.body(new ParameterizedTypeReference<>() {});
+
+		assertThat(articles).isEqualTo(List.of());
+	}
+}