Declare Advisor#isPerInstance() as default method

Includes INSTANCE constants on default factory classes.

Closes spring-projectsgh-30614

spring-aop/src/main/java/org/springframework/aop/Advisor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -62,8 +62,11 @@ public interface Advisor {
 	 * Typical Advisor implementations always return {@code true}.
 	 * Use singleton/prototype bean definitions or appropriate programmatic
 	 * proxy creation to ensure that Advisors have the correct lifecycle model.
+	 * <p>As of 6.0.10, the default implementation returns {@code true}.
 	 * @return whether this advice is associated with a particular target instance
 	 */
-	boolean isPerInstance();
+	default boolean isPerInstance() {
+		return true;
+	}
 
 }

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

@@ -67,11 +67,6 @@ public int getOrder() {
 		}
 	}
 
-	@Override
-	public boolean isPerInstance() {
-		return true;
-	}
-
 	@Override
 	public Advice getAdvice() {
 		return this.advice;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -91,11 +91,6 @@ public void validateInterfaces() throws IllegalArgumentException {
 		// Do nothing
 	}
 
-	@Override
-	public boolean isPerInstance() {
-		return true;
-	}
-
 	@Override
 	public Advice getAdvice() {
 		return this.advice;

spring-aop/src/main/java/org/springframework/aop/framework/DefaultAdvisorChainFactory.java

@@ -47,6 +47,13 @@
 @SuppressWarnings("serial")
 public class DefaultAdvisorChainFactory implements AdvisorChainFactory, Serializable {
 
+	/**
+	 * Singleton instance of this class.
+	 * @since 6.0.10
+	 */
+	public static final DefaultAdvisorChainFactory INSTANCE = new DefaultAdvisorChainFactory();
+
+
 	@Override
 	public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
 			Advised config, Method method, @Nullable Class<?> targetClass) {

spring-aop/src/main/java/org/springframework/aop/framework/DefaultAopProxyFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -48,6 +48,12 @@
  */
 public class DefaultAopProxyFactory implements AopProxyFactory, Serializable {
 
+	/**
+	 * Singleton instance of this class.
+	 * @since 6.0.10
+	 */
+	public static final DefaultAopProxyFactory INSTANCE = new DefaultAopProxyFactory();
+
 	private static final long serialVersionUID = 7930414337282325166L;
 
 

spring-aop/src/main/java/org/springframework/aop/framework/ProxyCreatorSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,7 +44,7 @@ public class ProxyCreatorSupport extends AdvisedSupport {
 	 * Create a new ProxyCreatorSupport instance.
 	 */
 	public ProxyCreatorSupport() {
-		this.aopProxyFactory = new DefaultAopProxyFactory();
+		this.aopProxyFactory = DefaultAopProxyFactory.INSTANCE;
 	}
 
 	/**

spring-aop/src/main/java/org/springframework/aop/framework/ProxyFactoryBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -606,11 +606,6 @@ public Advice getAdvice() {
 			throw new UnsupportedOperationException("Cannot invoke methods: " + this.message);
 		}
 
-		@Override
-		public boolean isPerInstance() {
-			throw new UnsupportedOperationException("Cannot invoke methods: " + this.message);
-		}
-
 		@Override
 		public String toString() {
 			return this.message;

spring-aop/src/main/java/org/springframework/aop/support/AbstractPointcutAdvisor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -58,22 +58,12 @@ public int getOrder() {
 		return Ordered.LOWEST_PRECEDENCE;
 	}
 
-	@Override
-	public boolean isPerInstance() {
-		return true;
-	}
-
 
 	@Override
 	public boolean equals(@Nullable Object other) {
-		if (this == other) {
-			return true;
-		}
-		if (!(other instanceof PointcutAdvisor otherAdvisor)) {
-			return false;
-		}
-		return (ObjectUtils.nullSafeEquals(getAdvice(), otherAdvisor.getAdvice()) &&
-				ObjectUtils.nullSafeEquals(getPointcut(), otherAdvisor.getPointcut()));
+		return (this == other || (other instanceof PointcutAdvisor otherAdvisor &&
+				ObjectUtils.nullSafeEquals(getAdvice(), otherAdvisor.getAdvice()) &&
+				ObjectUtils.nullSafeEquals(getPointcut(), otherAdvisor.getPointcut())));
 	}
 
 	@Override

spring-aop/src/main/java/org/springframework/aop/support/DefaultIntroductionAdvisor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -134,11 +134,6 @@ public Advice getAdvice() {
 		return this.advice;
 	}
 
-	@Override
-	public boolean isPerInstance() {
-		return true;
-	}
-
 	@Override
 	public ClassFilter getClassFilter() {
 		return this;
@@ -152,13 +147,9 @@ public boolean matches(Class<?> clazz) {
 
 	@Override
 	public boolean equals(@Nullable Object other) {
-		if (this == other) {
-			return true;
-		}
-		if (!(other instanceof DefaultIntroductionAdvisor otherAdvisor)) {
-			return false;
-		}
-		return (this.advice.equals(otherAdvisor.advice) && this.interfaces.equals(otherAdvisor.interfaces));
+		return (this == other || (other instanceof DefaultIntroductionAdvisor otherAdvisor &&
+				this.advice.equals(otherAdvisor.advice) &&
+				this.interfaces.equals(otherAdvisor.interfaces)));
 	}
 
 	@Override

spring-aop/src/main/java/org/springframework/aop/support/StaticMethodMatcherPointcutAdvisor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -77,11 +77,6 @@ public Advice getAdvice() {
 		return this.advice;
 	}
 
-	@Override
-	public boolean isPerInstance() {
-		return true;
-	}
-
 	@Override
 	public Pointcut getPointcut() {
 		return this;