From 1cdd56bf024845553d78e574dfe420cd04912998 Mon Sep 17 00:00:00 2001
From: Sam Brannen <104798+sbrannen@users.noreply.github.com>
Date: Fri, 3 Oct 2025 13:57:01 +0200
Subject: [PATCH] Log multiple primary bean detection in
 DefaultListableBeanFactory

Prior to this commit, a NoUniqueBeanDefinitionException was thrown when
multiple primary beans were detected within a given set of beans, but
nothing was logged. For use cases where the exception is handled by
infrastructure code, it may not be obvious to the developer what the
problem is.

To address that, a TRACE message is now logged whenever multiple
competing primary beans are detected in DefaultListableBeanFactory.

Closes gh-35550
---
 .../beans/factory/support/DefaultListableBeanFactory.java    | 5 +++--
 .../beans/factory/DefaultListableBeanFactoryTests.java       | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java b/spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java
index 2c67f665511..80e24655bf1 100644
--- a/spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java
+++ b/spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java
@@ -2098,8 +2098,9 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 					boolean candidateLocal = containsBeanDefinition(candidateBeanName);
 					boolean primaryLocal = containsBeanDefinition(primaryBeanName);
 					if (candidateLocal == primaryLocal) {
-						throw new NoUniqueBeanDefinitionException(requiredType, candidates.size(),
-								"more than one 'primary' bean found among candidates: " + candidates.keySet());
+						String message = "more than one 'primary' bean found among candidates: " + candidates.keySet();
+						logger.trace(message);
+						throw new NoUniqueBeanDefinitionException(requiredType, candidates.size(), message);
 					}
 					else if (candidateLocal) {
 						primaryBeanName = candidateBeanName;
diff --git a/spring-beans/src/test/java/org/springframework/beans/factory/DefaultListableBeanFactoryTests.java b/spring-beans/src/test/java/org/springframework/beans/factory/DefaultListableBeanFactoryTests.java
index dc964ad5ff4..c85c9493216 100644
--- a/spring-beans/src/test/java/org/springframework/beans/factory/DefaultListableBeanFactoryTests.java
+++ b/spring-beans/src/test/java/org/springframework/beans/factory/DefaultListableBeanFactoryTests.java
@@ -1798,7 +1798,7 @@ class DefaultListableBeanFactoryTests {
 
 		assertThatExceptionOfType(NoUniqueBeanDefinitionException.class)
 				.isThrownBy(() -> lbf.getBean(TestBean.class))
-				.withMessageContaining("more than one 'primary'");
+				.withMessageEndingWith("more than one 'primary' bean found among candidates: [bd1, bd2]");
 	}
 
 	@Test
@@ -2122,7 +2122,7 @@ class DefaultListableBeanFactoryTests {
 
 		assertThatExceptionOfType(NoUniqueBeanDefinitionException.class)
 				.isThrownBy(() -> lbf.getBean(ConstructorDependency.class, 42))
-				.withMessageContaining("more than one 'primary'");
+				.withMessageEndingWith("more than one 'primary' bean found among candidates: [bd1, bd2]");
 	}
 
 	@Test