Added a test to verify the instrumentation support for the Spring HTTP client RestClient.

apm-agent-plugins/apm-spring-resttemplate/apm-spring-restclient-test/pom.xml

@@ -0,0 +1,59 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>co.elastic.apm</groupId>
+        <artifactId>apm-spring-resttemplate</artifactId>
+        <version>1.44.1-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>apm-spring-restclient-test</artifactId>
+    <name>${project.groupId}:${project.artifactId}</name>
+
+    <properties>
+        <apm-agent-parent.base.dir>${project.basedir}/../../..</apm-agent-parent.base.dir>
+    </properties>
+
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-dependencies</artifactId>
+                <version>3.2.0</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-webmvc</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>apm-spring-resttemplate-plugin</artifactId>
+            <version>${project.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>apm-spring-resttemplate-plugin</artifactId>
+            <version>${project.version}</version>
+            <type>test-jar</type>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>apm-httpclient-core</artifactId>
+            <version>${project.version}</version>
+            <type>test-jar</type>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>

apm-agent-plugins/apm-spring-resttemplate/apm-spring-restclient-test/src/test/java/co/elastic/apm/agent/restclient/SpringRestClientInstrumentationTest.java

@@ -0,0 +1,83 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package co.elastic.apm.agent.restclient;
+
+import co.elastic.apm.agent.common.JvmRuntimeInfo;
+import co.elastic.apm.agent.httpclient.AbstractHttpClientInstrumentationTest;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.springframework.web.client.RestClient;
+import org.springframework.web.client.RestTemplate;
+
+import java.util.List;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+@RunWith(Parameterized.class)
+public class SpringRestClientInstrumentationTest extends AbstractHttpClientInstrumentationTest {
+
+    // Cannot directly reference RestTemplate here because it is compiled with Java 17
+    private final Object restClient;
+    private final Boolean isRedirectFollowingSupported;
+
+    public SpringRestClientInstrumentationTest(Supplier<RestClient> supplier,
+                                               Boolean isRedirectFollowingSupported) {
+        this.restClient = supplier.get();
+        this.isRedirectFollowingSupported = isRedirectFollowingSupported;
+    }
+
+    @Parameterized.Parameters()
+    public static Iterable<Object[]> data() {
+        if (JvmRuntimeInfo.ofCurrentVM().getMajorVersion() >= 17) {
+            return SpringRestClientInstrumentationTest.Java17Code.getRestClient();
+        } else {
+            return List.of();
+        }
+    }
+
+    @Override
+    protected void performGet(String path) {
+        Java17Code.performGet(restClient, path);
+    }
+
+    @Override
+    protected boolean isRedirectFollowingSupported() {
+        return isRedirectFollowingSupported;
+    }
+
+    /**
+     * The code is compiled with java 17 but potentially run with java 11.
+     * JUnit will inspect the test class, therefore it must not contain any references to java 17 code.
+     */
+    private static class Java17Code {
+        public static void performGet(Object restClient, String path) {
+            ((RestClient) restClient).get().uri(path).retrieve().body(String.class);
+        }
+
+        public static Iterable<Object[]> getRestClient() {
+            Supplier<RestClient> defaultRestClient = () -> RestClient.create();
+            Supplier<RestClient> restTemplateBasedRestClient = () -> RestClient.create(new RestTemplate());
+            return Stream.of(
+                    new Object[][]{{defaultRestClient, false},
+                        {restTemplateBasedRestClient, true}})
+                .collect(Collectors.toList());
+        }
+    }
+}

apm-agent-plugins/apm-spring-resttemplate/pom.xml

@@ -19,6 +19,7 @@
     <modules>
         <module>apm-spring-resttemplate-plugin</module>
         <module>apm-spring-resttemplate-test</module>
+        <module>apm-spring-restclient-test</module>
     </modules>
 
 </project>

docs/supported-technologies.asciidoc

@@ -386,6 +386,11 @@ The spans are named after the schema `<method> <host>`, for example `GET elastic
 |
 |
 | 1.36.0
+
+|Spring RestClient
+|6.1.0+
+|
+|1.44.0
 |===