DATACMNS-1768 - Reuse bean state in InstantiationAwarePropertyAccessor when setting multiple properties.

We now reuse the new bean in InstantiationAwarePropertyAccessor when setting properties. Previously, we used the initial bean state as the bean was held by a delegate PersistentPropertyAccessor which caused only the last set property to be visible.

src/main/java/org/springframework/data/mapping/model/InstantiationAwarePropertyAccessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019 the original author or authors.
+ * Copyright 2019-2020 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.
@@ -15,6 +15,8 @@
  */
 package org.springframework.data.mapping.model;
 
+import java.util.function.Function;
+
 import org.springframework.data.annotation.PersistenceConstructor;
 import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.PersistentProperty;
@@ -31,13 +33,15 @@ import org.springframework.util.Assert;
  * {@link PersistentProperty} is to be applied on a completely immutable entity type exposing a persistence constructor.
  *
  * @author Oliver Drotbohm
+ * @author Mark Paluch
+ * @since 2.3
  */
 public class InstantiationAwarePropertyAccessor<T> implements PersistentPropertyAccessor<T> {
 
 	private static final String NO_SETTER_OR_CONSTRUCTOR = "Cannot set property %s because no setter, wither or copy constructor exists for %s!";
 	private static final String NO_CONSTRUCTOR_PARAMETER = "Cannot set property %s because no setter, no wither and it's not part of the persistence constructor %s!";
 
-	private final PersistentPropertyAccessor<T> delegate;
+	private final Function<T, PersistentPropertyAccessor<T>> delegateFunction;
 	private final EntityInstantiators instantiators;
 
 	private T bean;
@@ -48,17 +52,41 @@ public class InstantiationAwarePropertyAccessor<T> implements PersistentProperty
 	 *
 	 * @param delegate must not be {@literal null}.
 	 * @param instantiators must not be {@literal null}.
+	 * @deprecated since 2.4. Using this constructor allows only setting a single property as
+	 *             {@link PersistentPropertyAccessor} holds a reference to the initial bean state.
 	 */
+	@Deprecated
 	public InstantiationAwarePropertyAccessor(PersistentPropertyAccessor<T> delegate, EntityInstantiators instantiators) {
 
-		Assert.notNull(delegate, "Delegate PersistenPropertyAccessor must not be null!");
+		Assert.notNull(delegate, "Delegate PersistentPropertyAccessor must not be null!");
 		Assert.notNull(instantiators, "EntityInstantiators must not be null!");
 
-		this.delegate = delegate;
 		this.instantiators = instantiators;
+		this.delegateFunction = t -> delegate;
 		this.bean = delegate.getBean();
 	}
 
+	/**
+	 * Creates an {@link InstantiationAwarePropertyAccessor} using the given delegate {@code accessorFunction} and
+	 * {@link EntityInstantiators}. {@code accessorFunction} is used to obtain a new {@link PersistentPropertyAccessor}
+	 * for each property to set.
+	 *
+	 * @param bean must not be {@literal null}.
+	 * @param accessorFunction must not be {@literal null}.
+	 * @param instantiators must not be {@literal null}.
+	 */
+	public InstantiationAwarePropertyAccessor(T bean, Function<T, PersistentPropertyAccessor<T>> accessorFunction,
+			EntityInstantiators instantiators) {
+
+		Assert.notNull(bean, "Bean must not be null!");
+		Assert.notNull(accessorFunction, "PersistentPropertyAccessor function must not be null!");
+		Assert.notNull(instantiators, "EntityInstantiators must not be null!");
+
+		this.delegateFunction = accessorFunction;
+		this.instantiators = instantiators;
+		this.bean = bean;
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mapping.PersistentPropertyAccessor#setProperty(org.springframework.data.mapping.PersistentProperty, java.lang.Object)
@@ -68,6 +96,7 @@ public class InstantiationAwarePropertyAccessor<T> implements PersistentProperty
 	public void setProperty(PersistentProperty<?> property, @Nullable Object value) {
 
 		PersistentEntity<?, ?> owner = property.getOwner();
+		PersistentPropertyAccessor<T> delegate = delegateFunction.apply(this.bean);
 
 		if (!property.isImmutable() || property.getWither() != null || ReflectionUtils.isKotlinClass(owner.getType())) {
 
@@ -123,7 +152,7 @@ public class InstantiationAwarePropertyAccessor<T> implements PersistentProperty
 	@Nullable
 	@Override
 	public Object getProperty(PersistentProperty<?> property) {
-		return delegate.getProperty(property);
+		return delegateFunction.apply(bean).getProperty(property);
 	}
 
 	/*

src/main/java/org/springframework/data/mapping/model/InstantiationAwarePropertyAccessorFactory.java

@@ -23,6 +23,8 @@ import org.springframework.data.mapping.PersistentPropertyAccessor;
  * an {@link InstantiationAwarePropertyAccessor} to allow the handling of purely immutable types.
  *
  * @author Oliver Drotbohm
+ * @author Mark Paluch
+ * @since 2.3
  */
 public class InstantiationAwarePropertyAccessorFactory implements PersistentPropertyAccessorFactory {
 
@@ -41,10 +43,8 @@ public class InstantiationAwarePropertyAccessorFactory implements PersistentProp
 	 */
 	@Override
 	public <T> PersistentPropertyAccessor<T> getPropertyAccessor(PersistentEntity<?, ?> entity, T bean) {
-
-		PersistentPropertyAccessor<T> accessor = delegate.getPropertyAccessor(entity, bean);
-
-		return new InstantiationAwarePropertyAccessor<>(accessor, instantiators);
+		return new InstantiationAwarePropertyAccessor<>(bean, it -> delegate.getPropertyAccessor(entity, it),
+				instantiators);
 	}
 
 	/*