Declare isStatic and releaseTarget as default methods on TargetSource

Closes gh-31820

Author: jhoeller

spring-aop/src/main/java/org/springframework/aop/TargetSource.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.
@@ -49,10 +49,13 @@ public interface TargetSource extends TargetClassAware {
 	 * Will all calls to {@link #getTarget()} return the same object?
 	 * <p>In that case, there will be no need to invoke {@link #releaseTarget(Object)},
 	 * and the AOP framework can cache the return value of {@link #getTarget()}.
+	 * <p>The default implementation returns {@code false}.
 	 * @return {@code true} if the target is immutable
 	 * @see #getTarget
 	 */
-	boolean isStatic();
+	default boolean isStatic() {
+		return false;
+	}
 
 	/**
 	 * Return a target instance. Invoked immediately before the
@@ -67,9 +70,11 @@ public interface TargetSource extends TargetClassAware {
 	/**
 	 * Release the given target object obtained from the
 	 * {@link #getTarget()} method, if any.
+	 * <p>The default implementation is empty.
 	 * @param target object obtained from a call to {@link #getTarget()}
 	 * @throws Exception if the object can't be released
 	 */
-	void releaseTarget(Object target) throws Exception;
+	default void releaseTarget(Object target) throws Exception {
+	}
 
 }

spring-aop/src/main/java/org/springframework/aop/target/AbstractBeanFactoryBasedTargetSource.java

@@ -153,16 +153,6 @@ public Class<?> getTargetClass() {
 		}
 	}
 
-	@Override
-	public boolean isStatic() {
-		return false;
-	}
-
-	@Override
-	public void releaseTarget(Object target) throws Exception {
-		// Nothing to do here.
-	}
-
 
 	/**
 	 * Copy configuration from the other AbstractBeanFactoryBasedTargetSource object.

spring-aop/src/main/java/org/springframework/aop/target/AbstractLazyCreationTargetSource.java

@@ -72,11 +72,6 @@ public synchronized Class<?> getTargetClass() {
 		return (this.lazyTarget != null ? this.lazyTarget.getClass() : null);
 	}
 
-	@Override
-	public boolean isStatic() {
-		return false;
-	}
-
 	/**
 	 * Returns the lazy-initialized target object,
 	 * creating it on-the-fly if it doesn't exist already.
@@ -91,11 +86,6 @@ public synchronized Object getTarget() throws Exception {
 		return this.lazyTarget;
 	}
 
-	@Override
-	public void releaseTarget(Object target) throws Exception {
-		// nothing to do
-	}
-
 
 	/**
 	 * Subclasses should implement this method to return the lazy initialized object.

spring-aop/src/main/java/org/springframework/aop/target/EmptyTargetSource.java

@@ -116,13 +116,6 @@ public Object getTarget() {
 		return null;
 	}
 
-	/**
-	 * Nothing to release.
-	 */
-	@Override
-	public void releaseTarget(Object target) {
-	}
-
 
 	/**
 	 * Returns the canonical instance on deserialization in case

spring-aop/src/main/java/org/springframework/aop/target/HotSwappableTargetSource.java

@@ -66,21 +66,11 @@ public synchronized Class<?> getTargetClass() {
 		return this.target.getClass();
 	}
 
-	@Override
-	public final boolean isStatic() {
-		return false;
-	}
-
 	@Override
 	public synchronized Object getTarget() {
 		return this.target;
 	}
 
-	@Override
-	public void releaseTarget(Object target) {
-		// nothing to do
-	}
-
 
 	/**
 	 * Swap the target, returning the old target object.

spring-aop/src/main/java/org/springframework/aop/target/SingletonTargetSource.java

@@ -67,11 +67,6 @@ public Object getTarget() {
 		return this.target;
 	}
 
-	@Override
-	public void releaseTarget(Object target) {
-		// nothing to do
-	}
-
 	@Override
 	public boolean isStatic() {
 		return true;

spring-aop/src/main/java/org/springframework/aop/target/dynamic/AbstractRefreshableTargetSource.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.
@@ -73,14 +73,6 @@ public synchronized Class<?> getTargetClass() {
 		return this.targetObject.getClass();
 	}
 
-	/**
-	 * Not static.
-	 */
-	@Override
-	public boolean isStatic() {
-		return false;
-	}
-
 	@Override
 	@Nullable
 	public final synchronized Object getTarget() {
@@ -90,13 +82,6 @@ public final synchronized Object getTarget() {
 		return this.targetObject;
 	}
 
-	/**
-	 * No need to release target.
-	 */
-	@Override
-	public void releaseTarget(Object object) {
-	}
-
 
 	@Override
 	public final synchronized void refresh() {

spring-aop/src/test/java/org/springframework/aop/target/PrototypeBasedTargetSourceTests.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.
@@ -75,14 +75,9 @@ private static class TestTargetSource extends AbstractPrototypeBasedTargetSource
 		private TestBean thisFieldIsNotSerializable = new TestBean();
 
 		@Override
-		public Object getTarget() throws Exception {
+		public Object getTarget() {
 			return newPrototypeInstance();
 		}
-
-		@Override
-		public void releaseTarget(Object target) throws Exception {
-			// Do nothing
-		}
 	}
 
 }

spring-context/src/main/java/org/springframework/context/annotation/ContextAnnotationAutowireCandidateResolver.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.
@@ -85,7 +85,7 @@ protected Object buildLazyResolutionProxy(DependencyDescriptor descriptor, @Null
 	}
 
 	private Object buildLazyResolutionProxy(
-			final DependencyDescriptor descriptor, final @Nullable String beanName, boolean classOnly) {
+			final DependencyDescriptor descriptor, @Nullable final String beanName, boolean classOnly) {
 
 		BeanFactory beanFactory = getBeanFactory();
 		Assert.state(beanFactory instanceof DefaultListableBeanFactory,
@@ -98,10 +98,6 @@ public Class<?> getTargetClass() {
 				return descriptor.getDependencyType();
 			}
 			@Override
-			public boolean isStatic() {
-				return false;
-			}
-			@Override
 			public Object getTarget() {
 				Set<String> autowiredBeanNames = (beanName != null ? new LinkedHashSet<>(1) : null);
 				Object target = dlbf.doResolveDependency(descriptor, beanName, autowiredBeanNames, null);
@@ -128,9 +124,6 @@ else if (Set.class == type || Collection.class == type) {
 				}
 				return target;
 			}
-			@Override
-			public void releaseTarget(Object target) {
-			}
 		};
 
 		ProxyFactory pf = new ProxyFactory();

spring-context/src/main/java/org/springframework/jndi/JndiObjectTargetSource.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.
@@ -148,8 +148,4 @@ public Object getTarget() {
 		}
 	}
 
-	@Override
-	public void releaseTarget(Object target) {
-	}
-
 }