Spring boot service name (#8006)

resolves #7998

---------

Co-authored-by: Mateusz Rzeszutek <mrzeszutek@splunk.com>
Co-authored-by: Lauri Tulmin <ltulmin@splunk.com>

instrumentation/spring/spring-boot-resources/library/src/main/java/io/opentelemetry/instrumentation/spring/resources/SpringBootServiceNameDetector.java

@@ -178,7 +178,8 @@ public class SpringBootServiceNameDetector implements ConditionalResourceProvide
     try {
       LoadSettings settings = LoadSettings.builder().build();
       Load yaml = new Load(settings);
-      Map<String, Object> data = (Map<String, Object>) yaml.loadFromInputStream(in);
+      for (Object o : yaml.loadAllFromInputStream(in)) {
+        Map<String, Object> data = (Map<String, Object>) o;
         Map<String, Map<String, Object>> spring =
             (Map<String, Map<String, Object>>) data.get("spring");
         if (spring != null) {
@@ -188,6 +189,7 @@ public class SpringBootServiceNameDetector implements ConditionalResourceProvide
             return (String) name;
           }
         }
+      }
     } catch (RuntimeException e) {
       // expected to fail sometimes
     }

instrumentation/spring/spring-boot-resources/library/src/test/java/io/opentelemetry/instrumentation/spring/resources/SpringBootServiceNameDetectorTest.java

@@ -75,6 +75,16 @@ class SpringBootServiceNameDetectorTest {
     expectServiceName(result, "cat-store");
   }
 
+  @Test
+  void classpathApplicationYamlContainingMultipleYamlDefinitions() {
+    when(system.openClasspathResource(APPLICATION_YML))
+        .thenReturn(
+            ClassLoader.getSystemClassLoader().getResourceAsStream("application-multi.yml"));
+    SpringBootServiceNameDetector guesser = new SpringBootServiceNameDetector(system);
+    Resource result = guesser.createResource(config);
+    expectServiceName(result, "cat-store");
+  }
+
   @Test
   void yamlFileInCurrentDir() throws Exception {
     Path yamlPath = Paths.get(APPLICATION_YML);

instrumentation/spring/spring-boot-resources/library/src/test/resources/application-multi.yml

@@ -0,0 +1,19 @@
+flib:
+  something:
+    12
+
+section:
+  two: 2
+
+server:
+  port: 777
+  context-path: /meow
+
+spring:
+  application:
+    name: cat-store
+
+---
+some:
+  other:
+    property: value