BAEL-9334: Resolving Apache HttpClient Error When Migrating Spring Bo…

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

@@ -83,6 +83,11 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>
         </dependency>
+
+        <dependency>
+            <groupId>org.apache.httpcomponents.client5</groupId>
+            <artifactId>httpclient5</artifactId>
+        </dependency>
     </dependencies>
 
     <profiles>

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

@@ -0,0 +1,55 @@
+package com.baeldung.restclient;
+
+import org.apache.hc.client5.http.config.ConnectionConfig;
+import org.apache.hc.client5.http.config.RequestConfig;
+import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
+import org.apache.hc.client5.http.impl.classic.HttpClients;
+import org.apache.hc.client5.http.impl.io.PoolingHttpClientConnectionManager;
+import org.apache.hc.client5.http.impl.io.PoolingHttpClientConnectionManagerBuilder;
+import org.apache.hc.core5.http.io.SocketConfig;
+import org.apache.hc.core5.util.Timeout;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
+import org.springframework.web.client.RestTemplate;
+
+@Configuration
+public class RestTemplateConfiguration {
+
+    @Bean
+    public RestTemplate restTemplate() {
+        try {
+            // Timeout configurations
+            SocketConfig socketConfig = SocketConfig.custom()
+              .setSoTimeout(Timeout.ofSeconds(30))  // Read timeout
+              .build();
+
+            ConnectionConfig connectionConfig = ConnectionConfig.custom()
+              .setConnectTimeout(Timeout.ofSeconds(30))  // Connect timeout
+              .build();
+
+            RequestConfig requestConfig = RequestConfig.custom()
+              .setConnectionRequestTimeout(Timeout.ofSeconds(30))  // Pool wait timeout
+              .build();
+
+            // Connection pool configuration
+            PoolingHttpClientConnectionManager connectionManager =
+              PoolingHttpClientConnectionManagerBuilder.create()
+                .setMaxConnPerRoute(20)
+                .setMaxConnTotal(100)
+                .setDefaultSocketConfig(socketConfig)
+                .setDefaultConnectionConfig(connectionConfig)
+                .build();
+
+            CloseableHttpClient httpClient = HttpClients.custom()
+              .setConnectionManager(connectionManager)
+              .setDefaultRequestConfig(requestConfig)
+              .build();
+
+            return new RestTemplate(new HttpComponentsClientHttpRequestFactory(httpClient));
+
+        } catch (Exception e) {
+            throw new IllegalStateException("Failed to configure RestTemplate", e);
+        }
+    }
+}

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

@@ -0,0 +1,40 @@
+package com.baeldung.restclient;
+
+import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.web.client.RestTemplate;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@SpringBootTest
+@ContextConfiguration(classes = RestTemplateConfiguration.class)
+public class RestTemplateConfigurationUnitTest {
+
+    @Autowired
+    private ApplicationContext context;
+
+    @Test
+    public void givenSpringContext_whenRestTemplateBeanRetrieved_thenReturnsProperlyConfiguredInstance() {
+        // When - We retrieve the RestTemplate bean
+        RestTemplate restTemplate = context.getBean(RestTemplate.class);
+
+        // Then - Verify it's properly configured
+        assertThat(restTemplate)
+                .isNotNull()
+                .extracting(RestTemplate::getRequestFactory)
+                .isInstanceOf(HttpComponentsClientHttpRequestFactory.class);
+
+        HttpComponentsClientHttpRequestFactory factory =
+                (HttpComponentsClientHttpRequestFactory) restTemplate.getRequestFactory();
+
+        assertThat(factory.getHttpClient())
+                .isInstanceOfSatisfying(CloseableHttpClient.class, client -> {
+                    assertThat(client).isNotNull();
+                });
+    }
+}