Search for @NoAutoStart annotations in ancestor hierarchy, implemented interfaces and meta-annotations (#531)

Adresses issue LOGBACK-1583

Signed-off-by: Bertrand Renuart <brenuart@gmail.com>
Co-authored-by: Ceki Gülcü <ceki@qos.ch>

Author: brenuart

logback-core/src/main/java/ch/qos/logback/core/joran/spi/NoAutoStartUtil.java

@@ -13,6 +13,10 @@
  */
 package ch.qos.logback.core.joran.spi;
 
+
+import java.lang.annotation.Annotation;
+import java.util.HashSet;
+import java.util.Set;
 import ch.qos.logback.core.spi.LifeCycle;
 
 public class NoAutoStartUtil {
@@ -24,13 +28,83 @@ public class NoAutoStartUtil {
      * @param o
      * @return true for classes not marked with the NoAutoStart annotation
      */
-    static public boolean notMarkedWithNoAutoStart(Object o) {
+    public static boolean notMarkedWithNoAutoStart(Object o) {
+        if (o == null) {
+            return false;
+        }
         Class<?> clazz = o.getClass();
-        NoAutoStart a = clazz.getAnnotation(NoAutoStart.class);
+        NoAutoStart a = findAnnotation(clazz, NoAutoStart.class);
         return a == null;
     }
 
-    /**
+	/**
+	 * Find a single {@link Annotation} of {@code annotationType} on the
+	 * supplied {@link Class}, traversing its interfaces, annotations, and
+	 * superclasses if the annotation is not <em>directly present</em> on
+	 * the given class itself.
+	 * <p>This method explicitly handles class-level annotations which are not
+	 * declared as {@link java.lang.annotation.Inherited inherited} <em>as well
+	 * as meta-annotations and annotations on interfaces</em>.
+	 * <p>The algorithm operates as follows:
+	 * <ol>
+	 * <li>Search for the annotation on the given class and return it if found.
+	 * <li>Recursively search through all annotations that the given class declares.
+	 * <li>Recursively search through all interfaces that the given class declares.
+	 * <li>Recursively search through the superclass hierarchy of the given class.
+	 * </ol>
+	 * <p>Note: in this context, the term <em>recursively</em> means that the search
+	 * process continues by returning to step #1 with the current interface,
+	 * annotation, or superclass as the class to look for annotations on.
+	 * @param clazz the class to look for annotations on
+	 * @param annotationType the type of annotation to look for
+	 * @return the first matching annotation, or {@code null} if not found
+	 */
+	private static <A extends Annotation> A findAnnotation(Class<?> clazz, Class<A> annotationType) {
+		return findAnnotation(clazz, annotationType, new HashSet<>());
+	}
+	
+	/**
+	 * Perform the search algorithm for {@link #findAnnotation(Class, Class)},
+	 * avoiding endless recursion by tracking which annotations have already
+	 * been <em>visited</em>.
+	 * @param clazz the class to look for annotations on
+	 * @param annotationType the type of annotation to look for
+	 * @param visited the set of annotations that have already been visited
+	 * @return the first matching annotation, or {@code null} if not found
+	 */
+	@SuppressWarnings("unchecked")
+	private static <A extends Annotation> A findAnnotation(Class<?> clazz, Class<A> annotationType, Set<Annotation> visited) {
+
+		Annotation[] anns = clazz.getDeclaredAnnotations();
+		for (Annotation ann : anns) {
+			if (ann.annotationType() == annotationType) {
+				return (A) ann;
+			}
+		}
+		for (Annotation ann : anns) {
+			if (visited.add(ann)) {
+				A annotation = findAnnotation(ann.annotationType(), annotationType, visited);
+				if (annotation != null) {
+					return annotation;
+				}
+			}
+		}
+
+		for (Class<?> ifc : clazz.getInterfaces()) {
+			A annotation = findAnnotation(ifc, annotationType, visited);
+			if (annotation != null) {
+				return annotation;
+			}
+		}
+
+		Class<?> superclass = clazz.getSuperclass();
+		if (superclass == null || Object.class == superclass) {
+			return null;
+		}
+		return findAnnotation(superclass, annotationType, visited);
+	}
+
+  /**
      * Is the object a {@link LifeCycle} and is it marked not marked with
      * the NoAutoStart annotation.
      * @param o
@@ -43,5 +117,4 @@ static public boolean shouldBeStarted(Object o) {
         } else
             return false;
     }
-
 }

logback-core/src/test/java/ch/qos/logback/core/joran/spi/NoAutoStartUtilTest.java

@@ -15,6 +15,12 @@
 
 import org.junit.jupiter.api.Test;
 
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.junit.Test;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -31,4 +37,71 @@ public void markedWithNoAutoStart() {
         DoNotAutoStart o = new DoNotAutoStart();
         assertFalse(NoAutoStartUtil.notMarkedWithNoAutoStart(o));
     }
+    
+
+    
+    /*
+     * Annotation declared on implemented interface
+     */
+    @Test
+    public void noAutoStartOnInterface() {
+    	ComponentWithNoAutoStartOnInterface o = new ComponentWithNoAutoStartOnInterface();
+        assertFalse(NoAutoStartUtil.notMarkedWithNoAutoStart(o));
+    }
+
+    @NoAutoStart
+    public interface NoAutoStartInterface {
+    }
+    
+    private static class ComponentWithNoAutoStartOnInterface implements NoAutoStartInterface {
+    }
+
+    
+    
+    /*
+     * Annotation declared on ancestor
+     */
+    @Test
+    public void noAutoStartOnAncestor() {
+    	ComponentWithNoAutoStartOnAncestor o = new ComponentWithNoAutoStartOnAncestor();
+        assertFalse(NoAutoStartUtil.notMarkedWithNoAutoStart(o));
+    }
+    
+    private static class ComponentWithNoAutoStartOnAncestor extends DoNotAutoStart {	
+    }
+
+    
+    
+    /*
+     * Annotation declared on interface implemented by an ancestor
+     */
+    @Test
+    public void noAutoStartOnInterfaceImplementedByAncestor() {
+    	ComponentWithAncestorImplementingInterfaceWithNoAutoStart o = new ComponentWithAncestorImplementingInterfaceWithNoAutoStart();
+        assertFalse(NoAutoStartUtil.notMarkedWithNoAutoStart(o));
+    }
+    
+    private static class ComponentWithAncestorImplementingInterfaceWithNoAutoStart extends ComponentWithNoAutoStartOnInterface {	
+    }
+    
+    
+
+    /*
+     * Custom annotation annotated with @NoAutoStart
+     */
+    @Test
+    public void noAutoStartAsMetaAnnotation() {
+    	ComponentWithMetaAnnotation o = new ComponentWithMetaAnnotation();
+        assertFalse(NoAutoStartUtil.notMarkedWithNoAutoStart(o));
+    }
+    
+    @Retention(RetentionPolicy.RUNTIME)
+    @Target(ElementType.TYPE)
+    @NoAutoStart
+    public @interface MetaNoAutoStart {
+    }
+    
+    @MetaNoAutoStart
+    private static class ComponentWithMetaAnnotation {
+    }
 }