From 66b9eab2c02a6720116cf23a0f7f7babf164c825 Mon Sep 17 00:00:00 2001
From: Henning Rohlfs <henning.rohlfs@innogames.com>
Date: Fri, 25 Sep 2020 16:58:55 +0200
Subject: [PATCH] DATACMNS-1806 - Prevent returning null from Lazy due to
 concurrency problem.

When accessed concurrently from multiple threads, Lazy.getNullable() could return null unexpectedly.

Original pull request: #468.
---
 src/main/java/org/springframework/data/util/Lazy.java | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/main/java/org/springframework/data/util/Lazy.java b/src/main/java/org/springframework/data/util/Lazy.java
index 75dda3485..2edcd8784 100644
--- a/src/main/java/org/springframework/data/util/Lazy.java
+++ b/src/main/java/org/springframework/data/util/Lazy.java
@@ -34,6 +34,7 @@ import org.springframework.util.Assert;
  *
  * @author Oliver Gierke
  * @author Mark Paluch
+ * @author Henning Rohlfs
  * @since 2.0
  */
 @RequiredArgsConstructor
@@ -45,7 +46,7 @@ public class Lazy<T> implements Supplier<T> {
 
 	private final Supplier<? extends T> supplier;
 	private @Nullable T value = null;
-	private boolean resolved = false;
+	private volatile boolean resolved = false;
 
 	/**
 	 * Creates a new {@link Lazy} to produce an object lazily.
@@ -203,15 +204,11 @@ public class Lazy<T> implements Supplier<T> {
 	@Nullable
 	public T getNullable() {
 
-		T value = this.value;
-
-		if (this.resolved) {
+		if (resolved) {
 			return value;
 		}
 
-		value = supplier.get();
-
-		this.value = value;
+		this.value = supplier.get();
 		this.resolved = true;
 
 		return value;