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

Author: sbrannen

spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java

@@ -2098,8 +2098,9 @@ protected String determinePrimaryCandidate(Map<String, Object> candidates, Class
 					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;

spring-beans/src/test/java/org/springframework/beans/factory/DefaultListableBeanFactoryTests.java

@@ -1798,7 +1798,7 @@ void getBeanByTypeWithMultiplePrimary() {
 
 		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 @@ void getBeanByTypeInstanceWithMultiplePrimary() {
 
 		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