GH-10083: Apply Nullability to core util package

Related to: #10083

* Add null checks and `@Nullable` where appropriate
* Handle optional `ErrorHandler` in `PartitionedDispatcher`
* Use `Objects.requireNonNull()` for reflection method lookups
* Add `Assert.notNull()` for UUID conversion

* Add `@Contract` to `UUIDConverter` methods
* Replace `Objects.requireNonNull` with ternary operator in `ClassUtils`

* Some minor code clean up

Signed-off-by: Jooyoung Pyoung <[email protected]>

Author: anthologia

spring-integration-core/src/main/java/org/springframework/integration/channel/ExecutorChannel.java

@@ -115,6 +115,8 @@ public final void onInit() {
 		Assert.state(getDispatcher().getHandlerCount() == 0, "You cannot subscribe() until the channel "
 				+ "bean is fully initialized by the framework. Do not subscribe in a @Bean definition");
 		super.onInit();
+
+		Assert.state(this.executor != null, "Executor must be configured");
 		if (!(this.executor instanceof ErrorHandlingTaskExecutor)) {
 			ErrorHandler errorHandler = ChannelUtils.getErrorHandler(getBeanFactory());
 			this.executor = new ErrorHandlingTaskExecutor(this.executor, errorHandler);

spring-integration-core/src/main/java/org/springframework/integration/dispatcher/PartitionedDispatcher.java

@@ -188,8 +188,11 @@ private void populatedPartitions() {
 	private UnicastingDispatcher newPartition() {
 		ExecutorService executor = Executors.newSingleThreadExecutor(this.threadFactory);
 		this.executors.add(executor);
-		DelegateDispatcher delegateDispatcher =
-				new DelegateDispatcher(new ErrorHandlingTaskExecutor(executor, this.errorHandler));
+
+		Executor effectiveExecutor = this.errorHandler != null
+				? new ErrorHandlingTaskExecutor(executor, this.errorHandler)
+				: executor;
+		DelegateDispatcher delegateDispatcher = new DelegateDispatcher(effectiveExecutor);
 		delegateDispatcher.setFailoverStrategy(this.failoverStrategy);
 		delegateDispatcher.setLoadBalancingStrategy(this.loadBalancingStrategy);
 		delegateDispatcher.setMessageHandlingTaskDecorator(this.messageHandlingTaskDecorator);

spring-integration-core/src/main/java/org/springframework/integration/util/AbstractExpressionEvaluator.java

@@ -54,8 +54,10 @@ public abstract class AbstractExpressionEvaluator implements BeanFactoryAware, I
 
 	private boolean simpleEvaluationContext;
 
+	@SuppressWarnings("NullAway.Init")
 	private volatile EvaluationContext evaluationContext;
 
+	@SuppressWarnings("NullAway.Init")
 	private volatile BeanFactory beanFactory;
 
 	private volatile MessageBuilderFactory messageBuilderFactory = new DefaultMessageBuilderFactory();

spring-integration-core/src/main/java/org/springframework/integration/util/BeanFactoryTypeConverter.java

@@ -40,6 +40,7 @@
  * @author Soby Chacko
  * @author Artem Bilan
  * @author Ngoc Nhan
+ * @author Jooyoung Pyoung
  */
 public class BeanFactoryTypeConverter implements TypeConverter, BeanFactoryAware {
 
@@ -86,7 +87,11 @@ public boolean canConvert(Class<?> sourceType, Class<?> targetType) {
 	}
 
 	@Override
-	public boolean canConvert(TypeDescriptor sourceTypeDescriptor, TypeDescriptor targetTypeDescriptor) {
+	public boolean canConvert(@Nullable TypeDescriptor sourceTypeDescriptor, TypeDescriptor targetTypeDescriptor) {
+		if (sourceTypeDescriptor == null) {
+			return true;
+		}
+
 		if (this.conversionService.canConvert(sourceTypeDescriptor, targetTypeDescriptor)) {
 			return true;
 		}
@@ -97,15 +102,17 @@ public boolean canConvert(TypeDescriptor sourceTypeDescriptor, TypeDescriptor ta
 	}
 
 	@Override // NOSONAR
-	public Object convertValue(Object value, TypeDescriptor sourceType, TypeDescriptor targetType) {
+	public @Nullable Object convertValue(@Nullable Object value, @Nullable TypeDescriptor sourceType,
+			TypeDescriptor targetType) {
+
 		// Echoes org.springframework.expression.common.ExpressionUtils.convertTypedValue()
 		if ((targetType.getType() == Void.class || targetType.getType() == Void.TYPE) && value == null) {
 			return null;
 		}
 		/*
 		 *  INT-2630 Spring 3.1 now converts ALL arguments; we know we don't need to convert MessageHeaders
 		 *  or MessageHistory; the MapToMap converter requires a no-arg constructor.
-		 *  Also INT-2650 - don't convert large byte[]
+		 *  Also, INT-2650 - don't convert large byte[]
 		 */
 		if (sourceType != null) {
 			Class<?> sourceClass = sourceType.getType();
@@ -120,19 +127,19 @@ public Object convertValue(Object value, TypeDescriptor sourceType, TypeDescript
 			return this.conversionService.convert(value, sourceType, targetType);
 		}
 
-		Object editorResult = valueFromEditorIfAny(value, sourceType.getType(), targetType);
-
-		if (editorResult == null) {
-			synchronized (this.delegate) {
-				return this.delegate.convertIfNecessary(value, targetType.getType());
+		if (sourceType != null) {
+			Object editorResult = valueFromEditorIfAny(value, sourceType.getType(), targetType);
+			if (editorResult != null) {
+				return editorResult;
 			}
 		}
-		else {
-			return editorResult;
+
+		synchronized (this.delegate) {
+			return this.delegate.convertIfNecessary(value, targetType.getType());
 		}
 	}
 
-	private PropertyEditor getDefaultEditor(Class<?> sourceType) {
+	private @Nullable PropertyEditor getDefaultEditor(Class<?> sourceType) {
 		PropertyEditor defaultEditor;
 		if (this.haveCalledDelegateGetDefaultEditor) {
 			defaultEditor = this.delegate.getDefaultEditor(sourceType);
@@ -147,8 +154,13 @@ private PropertyEditor getDefaultEditor(Class<?> sourceType) {
 		return defaultEditor;
 	}
 
-	@Nullable
-	private Object valueFromEditorIfAny(Object value, Class<?> sourceClass, TypeDescriptor targetType) {
+	private @Nullable Object valueFromEditorIfAny(@Nullable Object value, @Nullable Class<?> sourceClass,
+			TypeDescriptor targetType) {
+
+		if (value == null || sourceClass == null) {
+			return null;
+		}
+
 		if (!String.class.isAssignableFrom(sourceClass)) {
 			PropertyEditor editor = this.delegate.findCustomEditor(sourceClass, null);
 			if (editor == null) {

spring-integration-core/src/main/java/org/springframework/integration/util/ClassUtils.java

@@ -20,6 +20,7 @@
 import java.lang.reflect.Proxy;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.function.Supplier;
@@ -46,12 +47,14 @@ public abstract class ClassUtils {
 	/**
 	 * The {@link Function#apply(Object)} method object.
 	 */
+	@SuppressWarnings("NullAway") // Reflection
 	public static final Method FUNCTION_APPLY_METHOD =
 			ReflectionUtils.findMethod(Function.class, "apply", (Class<?>[]) null);
 
 	/**
 	 * The {@link Supplier#get()} method object.
 	 */
+	@SuppressWarnings("NullAway") // Reflection
 	public static final Method SUPPLIER_GET_METHOD =
 			ReflectionUtils.findMethod(Supplier.class, "get", (Class<?>[]) null);
 
@@ -73,17 +76,17 @@ public abstract class ClassUtils {
 	/**
 	 * The {@code kotlin.jvm.functions.Function0} class object.
 	 */
-	public static final Class<?> KOTLIN_FUNCTION_0_CLASS;
+	public static final @Nullable Class<?> KOTLIN_FUNCTION_0_CLASS;
 
 	/**
 	 * The {@code kotlin.jvm.functions.Function0#invoke} method object.
 	 */
-	public static final Method KOTLIN_FUNCTION_0_INVOKE_METHOD;
+	public static final @Nullable Method KOTLIN_FUNCTION_0_INVOKE_METHOD;
 
 	/**
 	 * The {@code kotlin.jvm.functions.Function1} class object.
 	 */
-	public static final Class<?> KOTLIN_FUNCTION_1_CLASS;
+	public static final @Nullable Class<?> KOTLIN_FUNCTION_1_CLASS;
 
 	static {
 		PRIMITIVE_WRAPPER_TYPE_MAP.put(Boolean.class, boolean.class);
@@ -107,7 +110,8 @@ public abstract class ClassUtils {
 			ReflectionUtils.rethrowRuntimeException(e);
 		}
 
-		SELECTOR_ACCEPT_METHOD = ReflectionUtils.findMethod(genericSelectorClass, "accept", (Class<?>[]) null);
+		SELECTOR_ACCEPT_METHOD =
+				Objects.requireNonNull(ReflectionUtils.findMethod(genericSelectorClass, "accept", (Class<?>[]) null));
 
 		Class<?> genericTransformerClass = null;
 		try {
@@ -120,7 +124,8 @@ public abstract class ClassUtils {
 		}
 
 		TRANSFORMER_TRANSFORM_METHOD =
-				ReflectionUtils.findMethod(genericTransformerClass, "transform", (Class<?>[]) null);
+				Objects.requireNonNull(
+						ReflectionUtils.findMethod(genericTransformerClass, "transform", (Class<?>[]) null));
 
 		Class<?> genericHandlerClass = null;
 		try {
@@ -132,7 +137,8 @@ public abstract class ClassUtils {
 			ReflectionUtils.rethrowRuntimeException(e);
 		}
 
-		HANDLER_HANDLE_METHOD = ReflectionUtils.findMethod(genericHandlerClass, "handle", (Class<?>[]) null);
+		HANDLER_HANDLE_METHOD =
+				Objects.requireNonNull(ReflectionUtils.findMethod(genericHandlerClass, "handle", (Class<?>[]) null));
 
 		if (KotlinDetector.isKotlinPresent()) {
 			Class<?> kotlinClass = null;
@@ -170,7 +176,8 @@ public abstract class ClassUtils {
 		}
 	}
 
-	public static Class<?> findClosestMatch(Class<?> type, Set<Class<?>> candidates, boolean failOnTie) {
+	@SuppressWarnings("NullAway")
+	public static @Nullable Class<?> findClosestMatch(Class<?> type, Set<Class<?>> candidates, boolean failOnTie) {
 		int minTypeDiffWeight = Integer.MAX_VALUE;
 		Class<?> closestMatch = null;
 		for (Class<?> candidate : candidates) {
@@ -181,8 +188,11 @@ public static Class<?> findClosestMatch(Class<?> type, Set<Class<?>> candidates,
 			}
 			else if (failOnTie && typeDiffWeight < Integer.MAX_VALUE && (typeDiffWeight == minTypeDiffWeight)) {
 				throw new IllegalStateException("Unresolvable ambiguity while attempting to find closest match for [" +
-						type.getName() + "]. Candidate types [" + closestMatch.getName() + "] and [" +
-						candidate.getName() + "] have equal weight.");
+						type.getName() + "]. Candidate types [" +
+						closestMatch.getName() +
+						"] and [" +
+						candidate.getName() +
+						"] have equal weight.");
 			}
 		}
 		return closestMatch;
@@ -219,8 +229,7 @@ else if (org.springframework.util.ClassUtils.isAssignable(candidate, superClass)
 	 * @param clazz the wrapper class to check
 	 * @return the corresponding primitive if the clazz is a wrapper, otherwise null
 	 */
-	@Nullable
-	public static Class<?> resolvePrimitiveType(Class<?> clazz) {
+	public static @Nullable Class<?> resolvePrimitiveType(Class<?> clazz) {
 		return PRIMITIVE_WRAPPER_TYPE_MAP.get(clazz);
 	}
 

spring-integration-core/src/main/java/org/springframework/integration/util/CompoundTrigger.java

@@ -18,6 +18,8 @@
 
 import java.time.Instant;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.scheduling.Trigger;
 import org.springframework.scheduling.TriggerContext;
 import org.springframework.util.Assert;
@@ -38,7 +40,7 @@ public class CompoundTrigger implements Trigger {
 
 	private volatile Trigger primary;
 
-	private volatile Trigger override;
+	private volatile @Nullable Trigger override;
 
 	/**
 	 * Construct a compound trigger with the supplied primary trigger.
@@ -62,12 +64,12 @@ public final void setPrimary(Trigger primary) {
 	 * primary trigger.
 	 * @param override the override trigger, or null.
 	 */
-	public void setOverride(Trigger override) {
+	public void setOverride(@Nullable Trigger override) {
 		this.override = override;
 	}
 
 	@Override
-	public Instant nextExecution(TriggerContext triggerContext) {
+	public @Nullable Instant nextExecution(TriggerContext triggerContext) {
 		if (this.override != null) {
 			return this.override.nextExecution(triggerContext);
 		}

spring-integration-core/src/main/java/org/springframework/integration/util/FunctionIterator.java

@@ -36,7 +36,7 @@
  */
 public class FunctionIterator<T, V> implements CloseableIterator<V> {
 
-	private final AutoCloseable closeable;
+	private final @Nullable AutoCloseable closeable;
 
 	private final Iterator<T> iterator;
 

spring-integration-core/src/main/java/org/springframework/integration/util/IntegrationReactiveUtils.java

@@ -74,7 +74,7 @@ public final class IntegrationReactiveUtils {
 	public static final boolean isContextPropagationPresent = ClassUtils.isPresent(
 			"io.micrometer.context.ContextSnapshot", IntegrationReactiveUtils.class.getClassLoader());
 
-	private static final ContextSnapshotFactory CONTEXT_SNAPSHOT_FACTORY =
+	private static final @Nullable ContextSnapshotFactory CONTEXT_SNAPSHOT_FACTORY =
 			isContextPropagationPresent ? ContextSnapshotFactory.builder().build() : null;
 
 	private IntegrationReactiveUtils() {
@@ -89,6 +89,10 @@ private IntegrationReactiveUtils() {
 	 * @since 6.2.5
 	 */
 	public static ContextView captureReactorContext() {
+		if (CONTEXT_SNAPSHOT_FACTORY == null) {
+			return Context.empty();
+		}
+
 		return isContextPropagationPresent
 				? CONTEXT_SNAPSHOT_FACTORY.captureAll().updateContext(Context.empty())
 				: Context.empty();
@@ -103,8 +107,10 @@ public static ContextView captureReactorContext() {
 	 * Or null if there is no {@code io.micrometer:context-propagation} library is on classpath.
 	 * @since 6.2.5
 	 */
-	@Nullable
-	public static AutoCloseable setThreadLocalsFromReactorContext(ContextView context) {
+	public static @Nullable AutoCloseable setThreadLocalsFromReactorContext(ContextView context) {
+		if (CONTEXT_SNAPSHOT_FACTORY == null) {
+			return null;
+		}
 		return isContextPropagationPresent ? CONTEXT_SNAPSHOT_FACTORY.setThreadLocalsFrom(context) : null;
 	}
 

spring-integration-core/src/main/java/org/springframework/integration/util/MessagingAnnotationUtils.java

@@ -34,6 +34,7 @@
 import org.springframework.core.annotation.MergedAnnotations;
 import org.springframework.integration.annotation.EndpointId;
 import org.springframework.integration.annotation.Payloads;
+import org.springframework.lang.Contract;
 import org.springframework.messaging.MessagingException;
 import org.springframework.messaging.handler.annotation.Header;
 import org.springframework.messaging.handler.annotation.Headers;
@@ -67,7 +68,7 @@ public final class MessagingAnnotationUtils {
 	 * @return The value.
 	 */
 	@SuppressWarnings("unchecked")
-	public static <T> T resolveAttribute(List<Annotation> annotations, String name, Class<T> requiredType) {
+	public static @Nullable <T> T resolveAttribute(List<Annotation> annotations, String name, Class<T> requiredType) {
 		for (Annotation annotation : annotations) {
 			Object value = AnnotationUtils.getValue(annotation, name);
 			if (requiredType.isInstance(value) && hasValue(value)) {
@@ -83,7 +84,7 @@ public static <T> T resolveAttribute(List<Annotation> annotations, String name,
 	 * @return {@code false} when {@code annotationValue} is null, an empty string, an empty array, or any annotation
 	 * whose 'value' field is set to {@link ValueConstants#DEFAULT_NONE} - {@code true} otherwise
 	 */
-	public static boolean hasValue(Object annotationValue) {
+	public static boolean hasValue(@Nullable Object annotationValue) {
 		if (annotationValue == null) {
 			return false;
 		}
@@ -100,7 +101,9 @@ public static boolean hasValue(Object annotationValue) {
 				!ValueConstants.DEFAULT_NONE.equals(AnnotationUtils.getValue((Annotation) annotationValue));
 	}
 
-	public static Method findAnnotatedMethod(Object target, final Class<? extends Annotation> annotationType) {
+	public static @Nullable Method findAnnotatedMethod(Object target,
+		final Class<? extends Annotation> annotationType) {
+
 		final AtomicReference<Method> reference = new AtomicReference<>();
 
 		ReflectionUtils.doWithMethods(AopProxyUtils.ultimateTargetClass(target),
@@ -120,7 +123,8 @@ public static Method findAnnotatedMethod(Object target, final Class<? extends An
 	 * @throws MessagingException if more than one of {@link Payload}, {@link Header}
 	 * or {@link Headers} annotations are presented.
 	 */
-	public static Annotation findMessagePartAnnotation(Annotation[] annotations, boolean payloads) {
+	@Contract("null, _ -> null")
+	public static @Nullable Annotation findMessagePartAnnotation(Annotation @Nullable [] annotations, boolean payloads) {
 		if (annotations == null || annotations.length == 0) {
 			return null;
 		}

spring-integration-core/src/main/java/org/springframework/integration/util/UUIDConverter.java

@@ -23,7 +23,10 @@
 import java.util.UUID;
 import java.util.regex.Pattern;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.core.convert.converter.Converter;
+import org.springframework.lang.Contract;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -45,7 +48,8 @@ public class UUIDConverter implements Converter<Object, UUID> {
 	 * @see org.springframework.core.convert.converter.Converter#convert(java.lang.Object)
 	 */
 	@Override
-	public UUID convert(Object source) {
+	@Contract("null -> null; !null -> !null")
+	public @Nullable UUID convert(@Nullable Object source) {
 		return getUUID(source);
 	}
 
@@ -63,7 +67,8 @@ public UUID convert(Object source) {
 	 * @param input an Object
 	 * @return a UUID constructed from the input
 	 */
-	public static UUID getUUID(Object input) {
+	@Contract("null -> null; !null -> !null")
+	public static @Nullable UUID getUUID(@Nullable Object input) {
 		if (input == null) {
 			return null;
 		}
@@ -89,7 +94,8 @@ private static UUID fromStringBytes(String input) {
 		return UUID.nameUUIDFromBytes(input.getBytes(StandardCharsets.UTF_8));
 	}
 
-	private static byte[] serialize(Object object) {
+	@Contract("null -> null; !null -> !null")
+	private static byte @Nullable [] serialize(@Nullable Object object) {
 		if (object == null) {
 			return null;
 		}