Fix potential NPE

This commit fixes a potential NPE when determining the priority of a
bean instance in case multiple candidates exist and no bean was marked
as @primary

Issue: SPR-12024

Author: snicoll

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

@@ -1205,7 +1205,7 @@ else if (candidatePriority < highestPriority) {
 	 * Return whether the bean definition for the given bean name has been
 	 * marked as a primary bean.
 	 * @param beanName the name of the bean
-	 * @param beanInstance the corresponding bean instance
+	 * @param beanInstance the corresponding bean instance (can be null)
 	 * @return whether the given bean qualifies as primary
 	 */
 	protected boolean isPrimary(String beanName, Object beanInstance) {
@@ -1221,11 +1221,14 @@ protected boolean isPrimary(String beanName, Object beanInstance) {
 	 * Return the priority assigned for the given bean instance by
 	 * the {@code javax.annotation.Priority} annotation.
 	 * <p>If the annotation is not present, returns {@code null}.
-	 * @param beanInstance the bean instance to check
+	 * @param beanInstance the bean instance to check (can be null)
 	 * @return the priority assigned to that bean or {@code null} if none is set
 	 */
 	protected Integer getPriority(Object beanInstance) {
-		return OrderUtils.getPriorityValue(beanInstance.getClass());
+		if (beanInstance != null) {
+			return OrderUtils.getPriorityValue(beanInstance.getClass());
+		}
+		return null;
 	}
 
 	/**

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

@@ -1403,6 +1403,17 @@ public void testGetBeanByTypeWithMultiplePriority() throws Exception {
 		lbf.getBean(TestBean.class);
 	}
 
+	@Test
+	public void testGetBeanByTypeWithPriorityAndNullInstance() throws Exception {
+		DefaultListableBeanFactory lbf = new DefaultListableBeanFactory();
+		RootBeanDefinition bd1 = new RootBeanDefinition(HighPriorityTestBean.class);
+		RootBeanDefinition bd2 = new RootBeanDefinition(NullTestBeanFactoryBean.class);
+		lbf.registerBeanDefinition("bd1", bd1);
+		lbf.registerBeanDefinition("bd2", bd2);
+		TestBean bean = lbf.getBean(TestBean.class);
+		assertThat(bean.getBeanName(), equalTo("bd1"));
+	}
+
 	@Test
 	public void testGetBeanByTypePrimaryHasPrecedenceOverPriority() throws Exception {
 		DefaultListableBeanFactory lbf = new DefaultListableBeanFactory();
@@ -2893,5 +2904,23 @@ private static class HighPriorityTestBean extends TestBean {}
 	@Priority(500)
 	private static class LowPriorityTestBean extends TestBean {}
 
+	private static class NullTestBeanFactoryBean<T> implements FactoryBean<TestBean> {
+
+		@Override
+		public TestBean getObject() throws Exception {
+			return null;
+		}
+
+		@Override
+		public Class<?> getObjectType() {
+			return TestBean.class;
+		}
+
+		@Override
+		public boolean isSingleton() {
+			return true;
+		}
+	}
+
 
 }