Apply external annotation instrumentation only to methods (open-telemetry#13948)

Author: laurit

instrumentation/external-annotations/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/extannotations/ExternalAnnotationInstrumentation.java

@@ -11,6 +11,7 @@
 import static net.bytebuddy.matcher.ElementMatchers.declaresMethod;
 import static net.bytebuddy.matcher.ElementMatchers.isAnnotatedWith;
 import static net.bytebuddy.matcher.ElementMatchers.isDeclaredBy;
+import static net.bytebuddy.matcher.ElementMatchers.isMethod;
 import static net.bytebuddy.matcher.ElementMatchers.namedOneOf;
 import static net.bytebuddy.matcher.ElementMatchers.none;
 import static net.bytebuddy.matcher.ElementMatchers.not;
@@ -109,7 +110,7 @@ public ElementMatcher<TypeDescription> typeMatcher() {
   @Override
   public void transform(TypeTransformer transformer) {
     transformer.applyAdviceToMethod(
-        isAnnotatedWith(traceAnnotationMatcher).and(not(excludedMethodsMatcher)),
+        isAnnotatedWith(traceAnnotationMatcher).and(not(excludedMethodsMatcher)).and(isMethod()),
         ExternalAnnotationInstrumentation.class.getName() + "$ExternalAnnotationAdvice");
   }
 

instrumentation/external-annotations/javaagent/src/test/java/io/opentelemetry/javaagent/instrumentation/extannotations/SayTracedHello.java

@@ -12,6 +12,12 @@
 @SuppressWarnings("UnnecessarilyFullyQualified")
 public class SayTracedHello {
 
+  public SayTracedHello() {}
+
+  // used to verify that constructor with tracing annotation doesn't break instrumentation
+  @com.appoptics.api.ext.LogMethod
+  public SayTracedHello(String unused) {}
+
   @com.appoptics.api.ext.LogMethod
   public String appoptics() {
     Span.current().setAttribute("providerAttr", "AppOptics");