Add nullability annotations to module/spring-boot-data-jpa

See gh-46587

module/spring-boot-data-jpa/src/main/java/org/springframework/boot/data/jpa/autoconfigure/JpaRepositoriesAutoConfiguration.java

@@ -20,6 +20,8 @@ import java.util.Map;
 
 import javax.sql.DataSource;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.AnyNestedCondition;
@@ -91,7 +93,7 @@ public final class JpaRepositoriesAutoConfiguration {
 		};
 	}
 
-	private AsyncTaskExecutor determineBootstrapExecutor(Map<String, AsyncTaskExecutor> taskExecutors) {
+	private @Nullable AsyncTaskExecutor determineBootstrapExecutor(Map<String, AsyncTaskExecutor> taskExecutors) {
 		if (taskExecutors.size() == 1) {
 			return taskExecutors.values().iterator().next();
 		}

module/spring-boot-data-jpa/src/main/java/org/springframework/boot/data/jpa/autoconfigure/JpaRepositoriesRegistrar.java

@@ -19,6 +19,8 @@ package org.springframework.boot.data.jpa.autoconfigure;
 import java.lang.annotation.Annotation;
 import java.util.Locale;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.autoconfigure.data.AbstractRepositoryConfigurationSourceSupport;
 import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
 import org.springframework.core.env.Environment;
@@ -38,7 +40,7 @@ import org.springframework.util.StringUtils;
  */
 class JpaRepositoriesRegistrar extends AbstractRepositoryConfigurationSourceSupport {
 
-	private BootstrapMode bootstrapMode = null;
+	private @Nullable BootstrapMode bootstrapMode;
 
 	@Override
 	protected Class<? extends Annotation> getAnnotation() {

module/spring-boot-data-jpa/src/main/java/org/springframework/boot/data/jpa/autoconfigure/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for Spring Data JPA.
  */
+@NullMarked
 package org.springframework.boot.data.jpa.autoconfigure;
+
+import org.jspecify.annotations.NullMarked;