From cb70fdb8e5c37cdd7e02cd2b16c6f6c8da7ca88f Mon Sep 17 00:00:00 2001
From: Matthew Miller <millem@amazon.com>
Date: Thu, 13 Jun 2024 11:45:34 -0700
Subject: [PATCH] Improve error message in JDK 17+ when concurrent
 modifications to SDK client builders cause a null value to be read.

---
 .../main/java/software/amazon/awssdk/utils/AttributeMap.java  | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/utils/src/main/java/software/amazon/awssdk/utils/AttributeMap.java b/utils/src/main/java/software/amazon/awssdk/utils/AttributeMap.java
index 5237f5da07b7..12eee34f0842 100644
--- a/utils/src/main/java/software/amazon/awssdk/utils/AttributeMap.java
+++ b/utils/src/main/java/software/amazon/awssdk/utils/AttributeMap.java
@@ -393,6 +393,10 @@ private <T> T internalGet(Value<?> requester, Key<T> key) {
          * Resolve the provided value, making sure to record any of its dependencies in the dependency graph.
          */
         private <T> T resolveValue(Value<T> value) {
+            Validate.notNull(value,
+                             "Encountered a null value when resolving configuration attributes. This is commonly "
+                             + "caused by concurrent modifications to non-thread-safe types. Ensure you're "
+                             + "synchronizing access to all non-thread-safe types.");
             return value.get(new LazyValueSource() {
                 @Override
                 public <U> U get(Key<U> innerKey) {