Refine null-safety in the spring-context module

Closes spring-projectsgh-34151

spring-context-support/src/main/java/org/springframework/cache/jcache/interceptor/AbstractJCacheOperation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -107,7 +107,7 @@ public CacheResolver getCacheResolver() {
 	}
 
 	@Override
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // https://github.com/uber/NullAway/issues/1113
 	public CacheInvocationParameter[] getAllParameters(@Nullable Object... values) {
 		if (this.allParameterDetails.size() != values.length) {
 			throw new IllegalStateException("Values mismatch, operation has " +

spring-context-support/src/main/java/org/springframework/cache/jcache/interceptor/DefaultJCacheOperationSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -182,7 +182,7 @@ protected <T> T getBean(Class<T> type) {
 		}
 	}
 
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	protected CacheManager getDefaultCacheManager() {
 		if (getCacheManager() == null) {
 			Assert.state(this.beanFactory != null, "BeanFactory required for default CacheManager resolution");
@@ -202,7 +202,7 @@ protected CacheManager getDefaultCacheManager() {
 	}
 
 	@Override
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	protected CacheResolver getDefaultCacheResolver() {
 		if (getCacheResolver() == null) {
 			this.cacheResolver = SingletonSupplier.of(new SimpleCacheResolver(getDefaultCacheManager()));
@@ -211,7 +211,7 @@ protected CacheResolver getDefaultCacheResolver() {
 	}
 
 	@Override
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	protected CacheResolver getDefaultExceptionCacheResolver() {
 		if (getExceptionCacheResolver() == null) {
 			this.exceptionCacheResolver = SingletonSupplier.of(new LazyCacheResolver());

spring-context-support/src/main/java/org/springframework/cache/jcache/interceptor/KeyGeneratorAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -84,7 +84,7 @@ public Object getTarget() {
 	}
 
 	@Override
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // https://github.com/uber/NullAway/issues/1113
 	public Object generate(Object target, Method method, @Nullable Object... params) {
 		JCacheOperation<?> operation = this.cacheOperationSource.getCacheOperation(method, target.getClass());
 		if (!(operation instanceof AbstractJCacheKeyOperation)) {

spring-context-support/src/main/java/org/springframework/scheduling/quartz/LocalDataSourceJobStore.java

@@ -90,7 +90,7 @@ public class LocalDataSourceJobStore extends JobStoreCMT {
 
 
 	@Override
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	public void initialize(ClassLoadHelper loadHelper, SchedulerSignaler signaler) throws SchedulerConfigException {
 		// Absolutely needs thread-bound DataSource to initialize.
 		this.dataSource = SchedulerFactoryBean.getConfigTimeDataSource();

spring-context-support/src/main/java/org/springframework/scheduling/quartz/SchedulerAccessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -194,7 +194,7 @@ public void setResourceLoader(ResourceLoader resourceLoader) {
 	/**
 	 * Register jobs and triggers (within a transaction, if possible).
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	protected void registerJobsAndTriggers() throws SchedulerException {
 		TransactionStatus transactionStatus = null;
 		if (this.transactionManager != null) {

spring-context-support/src/main/java/org/springframework/scheduling/quartz/SchedulerFactoryBean.java

@@ -644,7 +644,7 @@ private Scheduler prepareScheduler(SchedulerFactory schedulerFactory) throws Sch
 	 * @see #afterPropertiesSet
 	 * @see org.quartz.SchedulerFactory#getScheduler
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	protected Scheduler createScheduler(SchedulerFactory schedulerFactory, @Nullable String schedulerName)
 			throws SchedulerException {
 

spring-context/src/main/java/org/springframework/cache/interceptor/SimpleKeyGenerator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -43,7 +43,7 @@
 public class SimpleKeyGenerator implements KeyGenerator {
 
 	@Override
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // https://github.com/uber/NullAway/issues/1113
 	public Object generate(Object target, Method method, @Nullable Object... params) {
 		return generateKey((KotlinDetector.isSuspendingFunction(method) ?
 				Arrays.copyOf(params, params.length - 1) : params));

spring-context/src/main/java/org/springframework/context/annotation/BeanMethod.java

@@ -45,7 +45,7 @@ final class BeanMethod extends ConfigurationMethod {
 
 
 	@Override
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Reflection
 	public void validate(ProblemReporter problemReporter) {
 		if (getMetadata().getAnnotationAttributes(Autowired.class.getName()) != null) {
 			// declared as @Autowired: semantic mismatch since @Bean method arguments are autowired

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClass.java

@@ -218,7 +218,7 @@ Map<ImportBeanDefinitionRegistrar, AnnotationMetadata> getImportBeanDefinitionRe
 		return this.importBeanDefinitionRegistrars;
 	}
 
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Reflection
 	void validate(ProblemReporter problemReporter) {
 		Map<String, Object> attributes = this.metadata.getAnnotationAttributes(Configuration.class.getName());
 

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassBeanDefinitionReader.java

@@ -291,7 +291,7 @@ private void loadBeanDefinitionsForBeanMethod(BeanMethod beanMethod) {
 		this.registry.registerBeanDefinition(beanName, beanDefToRegister);
 	}
 
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Reflection
 	protected boolean isOverriddenByExistingDefinition(BeanMethod beanMethod, String beanName) {
 		if (!this.registry.containsBeanDefinition(beanName)) {
 			return false;

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassParser.java

@@ -821,12 +821,12 @@ void register(DeferredImportSelectorHolder deferredImport) {
 					deferredImport.getConfigurationClass());
 		}
 
-		@SuppressWarnings("NullAway")
 		void processGroupImports() {
 			for (DeferredImportSelectorGrouping grouping : this.groupings.values()) {
 				Predicate<String> filter = grouping.getCandidateFilter();
 				grouping.getImports().forEach(entry -> {
 					ConfigurationClass configurationClass = this.configurationClasses.get(entry.getMetadata());
+					Assert.state(configurationClass != null, "ConfigurationClass must not be null");
 					try {
 						processImports(configurationClass, asSourceClass(configurationClass, filter),
 								Collections.singleton(asSourceClass(entry.getImportClassName(), filter)),

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassPostProcessor.java

@@ -319,7 +319,7 @@ public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
 	}
 
 	@Override
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Lazy initialization
 	public @Nullable BeanFactoryInitializationAotContribution processAheadOfTime(ConfigurableListableBeanFactory beanFactory) {
 		boolean hasPropertySourceDescriptors = !CollectionUtils.isEmpty(this.propertySourceDescriptors);
 		boolean hasImportRegistry = beanFactory.containsBean(IMPORT_REGISTRY_BEAN_NAME);

spring-context/src/main/java/org/springframework/context/annotation/ContextAnnotationAutowireCandidateResolver.java

@@ -127,7 +127,6 @@ public Class<?> getTargetClass() {
 		}
 
 		@Override
-		@SuppressWarnings("NullAway")
 		public Object getTarget() {
 			Object cachedTarget = this.cachedTarget;
 			if (cachedTarget != null) {

spring-context/src/main/java/org/springframework/context/annotation/ProfileCondition.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,7 +31,7 @@
 class ProfileCondition implements Condition {
 
 	@Override
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Reflection
 	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
 		MultiValueMap<String, Object> attrs = metadata.getAllAnnotationAttributes(Profile.class.getName());
 		if (attrs != null) {

spring-context/src/main/java/org/springframework/context/event/AbstractApplicationEventMulticaster.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -229,7 +229,7 @@ protected Collection<ApplicationListener<?>> getApplicationListeners(
 	 * @param retriever the ListenerRetriever, if supposed to populate one (for caching purposes)
 	 * @return the pre-filtered list of application listeners for the given event and source type
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	private Collection<ApplicationListener<?>> retrieveApplicationListeners(
 			ResolvableType eventType, @Nullable Class<?> sourceType, @Nullable CachedListenerRetriever retriever) {
 

spring-context/src/main/java/org/springframework/format/datetime/standard/DateTimeFormatterRegistrar.java

@@ -51,7 +51,7 @@
  * @see org.springframework.format.FormatterRegistrar#registerFormatters
  * @see org.springframework.format.datetime.DateFormatterRegistrar
  */
-@SuppressWarnings("NullAway")
+@SuppressWarnings("NullAway") // Well-known map keys
 public class DateTimeFormatterRegistrar implements FormatterRegistrar {
 
 	private enum Type {DATE, TIME, DATE_TIME}

spring-context/src/main/java/org/springframework/jmx/export/MBeanExporter.java

@@ -987,7 +987,6 @@ private void registerNotificationListeners() throws MBeanExportException {
 	 * Unregister the configured {@link NotificationListener NotificationListeners}
 	 * from the {@link MBeanServer}.
 	 */
-	@SuppressWarnings("NullAway")
 	private void unregisterNotificationListeners() {
 		if (this.server != null) {
 			this.registeredNotificationListeners.forEach((bean, mappedObjectNames) -> {

spring-context/src/main/java/org/springframework/validation/DataBinder.java

@@ -669,7 +669,6 @@ public void setValidator(@Nullable Validator validator) {
 		}
 	}
 
-	@SuppressWarnings("NullAway")
 	private void assertValidators(@Nullable Validator... validators) {
 		Object target = getTarget();
 		for (Validator validator : validators) {
@@ -728,7 +727,6 @@ public List<Validator> getValidators() {
 	 * {@link #setExcludedValidators(Predicate) exclude predicate}.
 	 * @since 6.1
 	 */
-	@SuppressWarnings("NullAway")
 	public List<Validator> getValidatorsToApply() {
 		return (this.excludedValidators != null ?
 				this.validators.stream().filter(validator -> !this.excludedValidators.test(validator)).toList() :
@@ -1232,7 +1230,7 @@ protected boolean isAllowed(String field) {
 	 * @see #getBindingErrorProcessor
 	 * @see BindingErrorProcessor#processMissingFieldError
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	protected void checkRequiredFields(MutablePropertyValues mpvs) {
 		String[] requiredFields = getRequiredFields();
 		if (!ObjectUtils.isEmpty(requiredFields)) {

spring-context/src/main/java/org/springframework/validation/DefaultMessageCodesResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -243,7 +243,6 @@ public String format(String errorCode, @Nullable String objectName, @Nullable St
 		 * {@link DefaultMessageCodesResolver#CODE_SEPARATOR}, skipping zero-length or
 		 * null elements altogether.
 		 */
-		@SuppressWarnings("NullAway")
 		public static String toDelimitedString(@Nullable String... elements) {
 			StringJoiner rtn = new StringJoiner(CODE_SEPARATOR);
 			for (String element : elements) {