Refine null-safety in the spring-orm module

Closes gh-34159

Author: sdeleuze

spring-orm/src/main/java/org/springframework/orm/hibernate5/HibernateJdbcException.java

@@ -42,15 +42,15 @@ public HibernateJdbcException(JDBCException ex) {
 	/**
 	 * Return the underlying SQLException.
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // JDBCException instances always have a non null cause
 	public SQLException getSQLException() {
 		return ((JDBCException) getCause()).getSQLException();
 	}
 
 	/**
 	 * Return the SQL that led to the problem.
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // JDBCException instances always have a non null cause
 	public @Nullable String getSql() {
 		return ((JDBCException) getCause()).getSQL();
 	}

spring-orm/src/main/java/org/springframework/orm/hibernate5/HibernateQueryException.java

@@ -39,9 +39,9 @@ public HibernateQueryException(QueryException ex) {
 	/**
 	 * Return the HQL query string that was invalid.
 	 */
-	@SuppressWarnings("NullAway")
 	public @Nullable String getQueryString() {
-		return ((QueryException) getCause()).getQueryString();
+		QueryException cause = (QueryException) getCause();
+		return cause == null ? null : cause.getQueryString();
 	}
 
 }

spring-orm/src/main/java/org/springframework/orm/jpa/persistenceunit/DefaultPersistenceUnitManager.java

@@ -435,7 +435,7 @@ public void afterPropertiesSet() {
 	 * @see #obtainDefaultPersistenceUnitInfo()
 	 * @see #obtainPersistenceUnitInfo(String)
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	public void preparePersistenceUnitInfos() {
 		this.persistenceUnitInfoNames.clear();
 		this.persistenceUnitInfos.clear();

spring-orm/src/main/java/org/springframework/orm/jpa/persistenceunit/PersistenceManagedTypesBeanRegistrationAotProcessor.java

@@ -238,13 +238,13 @@ private void contributeHibernateHints(RuntimeHints hints, @Nullable ClassLoader
 			}
 		}
 
-		@SuppressWarnings("NullAway")
+		@SuppressWarnings("NullAway") // Not null assertion performed in ReflectionHints.registerType
 		private void registerForReflection(ReflectionHints reflection, @Nullable Annotation annotation, String attribute) {
 			if (annotation == null) {
 				return;
 			}
-			Class<?> embeddableInstantiatorClass = (Class<?>) AnnotationUtils.getAnnotationAttributes(annotation).get(attribute);
-			reflection.registerType(embeddableInstantiatorClass, MemberCategory.INVOKE_DECLARED_CONSTRUCTORS);
+			Class<?> type = (Class<?>) AnnotationUtils.getAnnotationAttributes(annotation).get(attribute);
+			reflection.registerType(type, MemberCategory.INVOKE_DECLARED_CONSTRUCTORS);
 		}
 	}
 }

spring-orm/src/main/java/org/springframework/orm/jpa/support/PersistenceAnnotationBeanPostProcessor.java

@@ -848,7 +848,7 @@ private CodeBlock generateResourceToInjectCode(
 			return CodeBlock.of("$L($L)", generatedMethod.getName(), REGISTERED_BEAN_PARAMETER);
 		}
 
-		@SuppressWarnings("NullAway")
+		@SuppressWarnings("NullAway") // Dataflow analysis limitation
 		private void generateGetEntityManagerMethod(MethodSpec.Builder method, PersistenceElement injectedElement) {
 			String unitName = injectedElement.unitName;
 			Properties properties = injectedElement.properties;