Refine allocation of DefaultMethodInvokingMethodInterceptor.

We now reduce allocations of DefaultMethodInvokingMethodInterceptor by reusing DefaultMethodInvokingMethodInterceptor within a ProxyProjectionFactory. We also reduced allocations during default method discovery and reuse the default methods information within the projection information cache.

Closes #2831

src/main/java/org/springframework/data/projection/DefaultMethodInvokingMethodInterceptor.java

@@ -23,10 +23,10 @@ import java.lang.reflect.Constructor;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.util.Map;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
-
 import org.springframework.aop.ProxyMethodInvocation;
 import org.springframework.data.util.Lazy;
 import org.springframework.lang.Nullable;
@@ -56,15 +56,10 @@ public class DefaultMethodInvokingMethodInterceptor implements MethodInterceptor
 	 */
 	public static boolean hasDefaultMethods(Class<?> interfaceClass) {
 
-		Method[] methods = ReflectionUtils.getAllDeclaredMethods(interfaceClass);
+		AtomicBoolean atomicBoolean = new AtomicBoolean();
+		ReflectionUtils.doWithMethods(interfaceClass, method -> atomicBoolean.set(true), Method::isDefault);
 
-		for (Method method : methods) {
-			if (method.isDefault()) {
-				return true;
-			}
-		}
-
-		return false;
+		return atomicBoolean.get();
 	}
 
 	/*

src/main/java/org/springframework/data/projection/ProxyProjectionFactory.java

@@ -29,6 +29,7 @@ import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.core.convert.support.GenericConversionService;
 import org.springframework.data.convert.Jsr310Converters;
+import org.springframework.data.util.Lazy;
 import org.springframework.data.util.NullableWrapperConverters;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -37,9 +38,9 @@ import org.springframework.util.ConcurrentReferenceHashMap;
 
 /**
  * A {@link ProjectionFactory} to create JDK proxies to back interfaces and handle method invocations on them. By
- * default accessor methods are supported. In case the delegating lookups result in an object of different type that the
- * projection interface method's return type, another projection will be created to transparently mitigate between the
- * types.
+ * default, accessor methods are supported. In case the delegating lookups result in an object of different type that
+ * the projection interface method's return type, another projection will be created to transparently mitigate between
+ * the types.
  *
  * @author Oliver Gierke
  * @author Christoph Strobl
@@ -59,9 +60,12 @@ class ProxyProjectionFactory implements ProjectionFactory, BeanClassLoaderAware
 	}
 
 	private final List<MethodInterceptorFactory> factories;
-	private final Map<Class<?>, ProjectionInformation> projectionInformationCache = new ConcurrentReferenceHashMap<>();
+	private final Map<Class<?>, ProjectionMetadata> projectionInformationCache = new ConcurrentReferenceHashMap<>();
 	private @Nullable ClassLoader classLoader;
 
+	private final Lazy<DefaultMethodInvokingMethodInterceptor> defaultMethodInvokingMethodInterceptor = Lazy
+			.of(DefaultMethodInvokingMethodInterceptor::new);
+
 	/**
 	 * Creates a new {@link ProxyProjectionFactory}.
 	 */
@@ -116,7 +120,12 @@ class ProxyProjectionFactory implements ProjectionFactory, BeanClassLoaderAware
 		factory.setOpaque(true);
 		factory.setInterfaces(projectionType, TargetAware.class);
 
-		factory.addAdvice(new DefaultMethodInvokingMethodInterceptor());
+		ProjectionMetadata projectionMetadata = getProjectionMetadata(projectionType);
+
+		if (projectionMetadata.hasDefaultMethods) {
+			factory.addAdvice(defaultMethodInvokingMethodInterceptor.get());
+		}
+
 		factory.addAdvice(new TargetAwareMethodInterceptor(source.getClass()));
 		factory.addAdvice(getMethodInterceptor(source, projectionType));
 
@@ -141,8 +150,12 @@ class ProxyProjectionFactory implements ProjectionFactory, BeanClassLoaderAware
 	 */
 	@Override
 	public final ProjectionInformation getProjectionInformation(Class<?> projectionType) {
+		return getProjectionMetadata(projectionType).projectionInformation;
+	}
 
-		return projectionInformationCache.computeIfAbsent(projectionType, this::createProjectionInformation);
+	private ProjectionMetadata getProjectionMetadata(Class<?> projectionType) {
+		return projectionInformationCache.computeIfAbsent(projectionType,
+				it -> ProjectionMetadata.create(it, createProjectionInformation(it)));
 	}
 
 	/**
@@ -310,4 +323,27 @@ class ProxyProjectionFactory implements ProjectionFactory, BeanClassLoaderAware
 			return true;
 		}
 	}
+
+	/**
+	 * Holder for {@link ProjectionInformation} and whether the target projection type uses {@code default} interface
+	 * methods.
+	 *
+	 * @since 2.7.13
+	 */
+	static class ProjectionMetadata {
+
+		final boolean hasDefaultMethods;
+
+		final ProjectionInformation projectionInformation;
+
+		ProjectionMetadata(boolean hasDefaultMethods, ProjectionInformation projectionInformation) {
+			this.hasDefaultMethods = hasDefaultMethods;
+			this.projectionInformation = projectionInformation;
+		}
+
+		public static ProjectionMetadata create(Class<?> projectionType, ProjectionInformation projectionInformation) {
+			return new ProjectionMetadata(DefaultMethodInvokingMethodInterceptor.hasDefaultMethods(projectionType),
+					projectionInformation);
+		}
+	}
 }

src/test/java/org/springframework/data/projection/ProxyProjectionFactoryUnitTests.java

@@ -139,16 +139,31 @@ class ProxyProjectionFactoryUnitTests {
 		assertThat(result).hasSize(6);
 	}
 
-	@Test // DATACMNS-655
+	@Test // DATACMNS-655, GH-2831
 	void invokesDefaultMethodOnProxy() {
 
+		CustomerExcerptWithDefaultMethod excerpt = factory.createProjection(CustomerExcerptWithDefaultMethod.class);
+
+		Advised advised = (Advised) ReflectionTestUtils.getField(Proxy.getInvocationHandler(excerpt), "advised");
+		Advisor[] advisors = advised.getAdvisors();
+
+		assertThat(advisors.length).isGreaterThan(0);
+		assertThat(advisors[0].getAdvice()).isInstanceOf(DefaultMethodInvokingMethodInterceptor.class);
+	}
+
+	@Test // GH-2831
+	void doesNotRegisterDefaultMethodInvokingMethodInterceptor() {
+
 		CustomerExcerpt excerpt = factory.createProjection(CustomerExcerpt.class);
 
 		Advised advised = (Advised) ReflectionTestUtils.getField(Proxy.getInvocationHandler(excerpt), "advised");
 		Advisor[] advisors = advised.getAdvisors();
 
 		assertThat(advisors.length).isGreaterThan(0);
-		assertThat(advisors[0].getAdvice()).isInstanceOf(DefaultMethodInvokingMethodInterceptor.class);
+
+		for (Advisor advisor : advisors) {
+			assertThat(advisor).isNotInstanceOf(DefaultMethodInvokingMethodInterceptor.class);
+		}
 	}
 
 	@Test // DATACMNS-648
@@ -273,8 +288,7 @@ class ProxyProjectionFactoryUnitTests {
 		customer.address.city = "New York";
 		customer.address.zipCode = "ZIP";
 
-		CustomerWithOptionalHavingProjection excerpt = factory.createProjection(CustomerWithOptionalHavingProjection.class,
-				customer);
+		CustomerWithOptionalHavingProjection excerpt = factory.createProjection(CustomerWithOptionalHavingProjection.class, customer);
 
 		assertThat(excerpt.getFirstname()).isEqualTo("Dave");
 		assertThat(excerpt.getAddress()).hasValueSatisfying(addressExcerpt -> {
@@ -345,6 +359,13 @@ class ProxyProjectionFactoryUnitTests {
 		Map<String, Object> getData();
 	}
 
+	interface CustomerExcerptWithDefaultMethod extends CustomerExcerpt {
+
+		default String getFirstnameAndId() {
+			return getFirstname() + " " + getId();
+		}
+	}
+
 	interface AddressExcerpt {
 
 		String getZipCode();