Leniently tolerate null bean as aspect instance

Closes gh-35074

Author: jhoeller

spring-aop/src/main/java/org/springframework/aop/aspectj/AbstractAspectJAdvice.java

@@ -618,28 +618,35 @@ else if (this.joinPointStaticPartArgumentIndex != -1) {
 	 * @return the invocation result
 	 * @throws Throwable in case of invocation failure
 	 */
-	protected Object invokeAdviceMethod(
-			@Nullable JoinPointMatch jpMatch, @Nullable Object returnValue, @Nullable Throwable ex)
-			throws Throwable {
+	protected @Nullable Object invokeAdviceMethod(@Nullable JoinPointMatch jpMatch,
+			@Nullable Object returnValue, @Nullable Throwable ex) throws Throwable {
 
 		return invokeAdviceMethodWithGivenArgs(argBinding(getJoinPoint(), jpMatch, returnValue, ex));
 	}
 
 	// As above, but in this case we are given the join point.
-	protected Object invokeAdviceMethod(JoinPoint jp, @Nullable JoinPointMatch jpMatch,
+	protected @Nullable Object invokeAdviceMethod(JoinPoint jp, @Nullable JoinPointMatch jpMatch,
 			@Nullable Object returnValue, @Nullable Throwable t) throws Throwable {
 
 		return invokeAdviceMethodWithGivenArgs(argBinding(jp, jpMatch, returnValue, t));
 	}
 
-	protected Object invokeAdviceMethodWithGivenArgs(Object[] args) throws Throwable {
+	protected @Nullable Object invokeAdviceMethodWithGivenArgs(Object[] args) throws Throwable {
 		Object[] actualArgs = args;
 		if (this.aspectJAdviceMethod.getParameterCount() == 0) {
 			actualArgs = null;
 		}
+		Object aspectInstance = this.aspectInstanceFactory.getAspectInstance();
+		if (aspectInstance.equals(null)) {
+			// Possibly a NullBean -> simply proceed if necessary.
+			if (getJoinPoint() instanceof ProceedingJoinPoint pjp) {
+				return pjp.proceed();
+			}
+			return null;
+		}
 		try {
 			ReflectionUtils.makeAccessible(this.aspectJAdviceMethod);
-			return this.aspectJAdviceMethod.invoke(this.aspectInstanceFactory.getAspectInstance(), actualArgs);
+			return this.aspectJAdviceMethod.invoke(aspectInstance, actualArgs);
 		}
 		catch (IllegalArgumentException ex) {
 			throw new AopInvocationException("Mismatch on arguments to advice method [" +

spring-aop/src/main/java/org/springframework/aop/aspectj/annotation/BeanFactoryAspectInstanceFactory.java

@@ -19,6 +19,7 @@
 import java.io.Serializable;
 
 import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.BeanNotOfRequiredTypeException;
 import org.springframework.beans.factory.config.ConfigurableBeanFactory;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.OrderUtils;
@@ -130,7 +131,12 @@ public int getOrder() {
 		Class<?> type = this.beanFactory.getType(this.name);
 		if (type != null) {
 			if (Ordered.class.isAssignableFrom(type) && this.beanFactory.isSingleton(this.name)) {
-				return ((Ordered) this.beanFactory.getBean(this.name)).getOrder();
+				try {
+					return this.beanFactory.getBean(this.name, Ordered.class).getOrder();
+				}
+				catch (BeanNotOfRequiredTypeException ex) {
+					// Not actually implementing Ordered -> possibly a NullBean.
+				}
 			}
 			return OrderUtils.getOrder(type, Ordered.LOWEST_PRECEDENCE);
 		}

spring-context/src/test/java/org/springframework/aop/aspectj/autoproxy/AspectJAutoProxyCreatorTests.java

@@ -364,6 +364,16 @@ void lambdaIsAlwaysProxiedWithJdkProxyWithIntroductions(Class<?> configClass) {
 		}
 	}
 
+	@Test
+	void nullAdviceIsSkipped() {
+		try (ConfigurableApplicationContext context = new AnnotationConfigApplicationContext(ProxyWithNullAdviceConfig.class)) {
+			@SuppressWarnings("unchecked")
+			Supplier<String> supplier = context.getBean(Supplier.class);
+			assertThat(AopUtils.isAopProxy(supplier)).as("AOP proxy").isTrue();
+			assertThat(supplier.get()).isEqualTo("lambda");
+		}
+	}
+
 	private ClassPathXmlApplicationContext newContext(String fileSuffix) {
 		return new ClassPathXmlApplicationContext(getClass().getSimpleName() + "-" + fileSuffix, getClass());
 	}
@@ -627,6 +637,16 @@ class ProxyTargetClassFalseConfig extends AbstractProxyTargetClassConfig {
 class ProxyTargetClassTrueConfig extends AbstractProxyTargetClassConfig {
 }
 
+@Configuration(proxyBeanMethods = false)
+@EnableAspectJAutoProxy(proxyTargetClass = true)
+class ProxyWithNullAdviceConfig extends AbstractProxyTargetClassConfig {
+
+	@Override
+	SupplierAdvice supplierAdvice() {
+		return null;
+	}
+}
+
 @Configuration
 @EnableAspectJAutoProxy(proxyTargetClass = true)
 class PerTargetProxyTargetClassTrueConfig {