Nullability refinements

See gh-32475

spring-core/src/main/java/org/springframework/core/ReactiveTypeDescriptor.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.
@@ -98,7 +98,9 @@ public boolean supportsEmpty() {
 	 */
 	public Object getEmptyValue() {
 		Assert.state(this.emptySupplier != null, "Empty values not supported");
-		return this.emptySupplier.get();
+		Object emptyValue = this.emptySupplier.get();
+		Assert.notNull(emptyValue, "Invalid null return value from emptySupplier");
+		return emptyValue;
 	}
 
 	/**

spring-core/src/main/java/org/springframework/core/ResolvableType.java

@@ -1118,22 +1118,21 @@ public static ResolvableType forClassWithGenerics(Class<?> clazz, Class<?>... ge
 	 * @return a {@code ResolvableType} for the specific class and generics
 	 * @see #forClassWithGenerics(Class, Class...)
 	 */
-	public static ResolvableType forClassWithGenerics(Class<?> clazz, ResolvableType... generics) {
+	public static ResolvableType forClassWithGenerics(Class<?> clazz, @Nullable ResolvableType... generics) {
 		Assert.notNull(clazz, "Class must not be null");
-		Assert.notNull(generics, "Generics array must not be null");
 		TypeVariable<?>[] variables = clazz.getTypeParameters();
-		Assert.isTrue(variables.length == generics.length,
-				() -> "Mismatched number of generics specified for " + clazz.toGenericString());
-
-		Type[] arguments = new Type[generics.length];
-		for (int i = 0; i < generics.length; i++) {
-			ResolvableType generic = generics[i];
+		if (generics != null) {
+			Assert.isTrue(variables.length == generics.length,
+					() -> "Mismatched number of generics specified for " + clazz.toGenericString());
+		}
+		Type[] arguments = new Type[variables.length];
+		for (int i = 0; i < variables.length; i++) {
+			ResolvableType generic = (generics != null ? generics[i] : null);
 			Type argument = (generic != null ? generic.getType() : null);
 			arguments[i] = (argument != null && !(argument instanceof TypeVariable) ? argument : variables[i]);
 		}
-
-		ParameterizedType syntheticType = new SyntheticParameterizedType(clazz, arguments);
-		return forType(syntheticType, new TypeVariablesVariableResolver(variables, generics));
+		return forType(new SyntheticParameterizedType(clazz, arguments),
+				(generics != null ? new TypeVariablesVariableResolver(variables, generics) : null));
 	}
 
 	/**
@@ -1388,7 +1387,7 @@ static ResolvableType forMethodParameter(
 	 */
 	public static ResolvableType forArrayComponent(ResolvableType componentType) {
 		Assert.notNull(componentType, "Component type must not be null");
-		Class<?> arrayType = componentType.resolve().arrayType();
+		Class<?> arrayType = componentType.toClass().arrayType();
 		return new ResolvableType(arrayType, componentType, null, null);
 	}
 

spring-core/src/main/java/org/springframework/core/annotation/AnnotatedMethod.java

@@ -278,6 +278,7 @@ public Class<?> getContainingClass() {
 		}
 
 		@Override
+		@Nullable
 		public <T extends Annotation> T getMethodAnnotation(Class<T> annotationType) {
 			return AnnotatedMethod.this.getMethodAnnotation(annotationType);
 		}

spring-core/src/main/java/org/springframework/core/annotation/AnnotationAttributes.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.
@@ -114,19 +114,6 @@ public AnnotationAttributes(Class<? extends Annotation> annotationType) {
 		this(annotationType, false);
 	}
 
-	/**
-	 * Create a new, empty {@link AnnotationAttributes} instance for the
-	 * specified {@code annotationType}.
-	 * @param annotationType the annotation type name represented by this
-	 * {@code AnnotationAttributes} instance; never {@code null}
-	 * @param classLoader the ClassLoader to try to load the annotation type on,
-	 * or {@code null} to just store the annotation type name
-	 * @since 4.3.2
-	 */
-	public AnnotationAttributes(String annotationType, @Nullable ClassLoader classLoader) {
-		this(getAnnotationType(annotationType, classLoader), false);
-	}
-
 	/**
 	 * Create a possibly already validated new, empty
 	 * {@link AnnotationAttributes} instance for the specified
@@ -143,6 +130,21 @@ public AnnotationAttributes(String annotationType, @Nullable ClassLoader classLo
 		this.validated = validated;
 	}
 
+	/**
+	 * Create a new, empty {@link AnnotationAttributes} instance for the
+	 * specified {@code annotationType}.
+	 * @param annotationType the annotation type name represented by this
+	 * {@code AnnotationAttributes} instance; never {@code null}
+	 * @param classLoader the ClassLoader to try to load the annotation type on,
+	 * or {@code null} to just store the annotation type name
+	 * @since 4.3.2
+	 */
+	public AnnotationAttributes(String annotationType, @Nullable ClassLoader classLoader) {
+		Assert.notNull(annotationType, "'annotationType' must not be null");
+		this.annotationType = getAnnotationType(annotationType, classLoader);
+		this.displayName = annotationType;
+		this.validated = false;
+	}
 
 	@SuppressWarnings("unchecked")
 	@Nullable
@@ -349,39 +351,29 @@ public <A extends Annotation> A[] getAnnotationArray(String attributeName, Class
 	private <T> T getRequiredAttribute(String attributeName, Class<T> expectedType) {
 		Assert.hasText(attributeName, "'attributeName' must not be null or empty");
 		Object value = get(attributeName);
-		assertAttributePresence(attributeName, value);
-		assertNotException(attributeName, value);
+		if (value == null) {
+			throw new IllegalArgumentException(String.format(
+					"Attribute '%s' not found in attributes for annotation [%s]",
+					attributeName, this.displayName));
+		}
+		if (value instanceof Throwable throwable) {
+			throw new IllegalArgumentException(String.format(
+					"Attribute '%s' for annotation [%s] was not resolvable due to exception [%s]",
+					attributeName, this.displayName, value), throwable);
+		}
 		if (!expectedType.isInstance(value) && expectedType.isArray() &&
 				expectedType.componentType().isInstance(value)) {
 			Object array = Array.newInstance(expectedType.componentType(), 1);
 			Array.set(array, 0, value);
 			value = array;
 		}
-		assertAttributeType(attributeName, value, expectedType);
-		return (T) value;
-	}
-
-	private void assertAttributePresence(String attributeName, Object attributeValue) {
-		Assert.notNull(attributeValue, () -> String.format(
-				"Attribute '%s' not found in attributes for annotation [%s]",
-				attributeName, this.displayName));
-	}
-
-	private void assertNotException(String attributeName, Object attributeValue) {
-		if (attributeValue instanceof Throwable throwable) {
-			throw new IllegalArgumentException(String.format(
-					"Attribute '%s' for annotation [%s] was not resolvable due to exception [%s]",
-					attributeName, this.displayName, attributeValue), throwable);
-		}
-	}
-
-	private void assertAttributeType(String attributeName, Object attributeValue, Class<?> expectedType) {
-		if (!expectedType.isInstance(attributeValue)) {
+		if (!expectedType.isInstance(value)) {
 			throw new IllegalArgumentException(String.format(
 					"Attribute '%s' is of type %s, but %s was expected in attributes for annotation [%s]",
-					attributeName, attributeValue.getClass().getSimpleName(), expectedType.getSimpleName(),
+					attributeName, value.getClass().getSimpleName(), expectedType.getSimpleName(),
 					this.displayName));
 		}
+		return (T) value;
 	}
 
 	@Override

spring-core/src/main/java/org/springframework/core/annotation/AnnotationUtils.java

@@ -985,8 +985,12 @@ public static void postProcessAnnotationAttributes(@Nullable Object annotatedEle
 		}
 	}
 
-	private static Object getAttributeValueForMirrorResolution(Method attribute, Object attributes) {
-		Object result = ((AnnotationAttributes) attributes).get(attribute.getName());
+	@Nullable
+	private static Object getAttributeValueForMirrorResolution(Method attribute, @Nullable Object attributes) {
+		if (!(attributes instanceof AnnotationAttributes annotationAttributes)) {
+			return null;
+		}
+		Object result = annotationAttributes.get(attribute.getName());
 		return (result instanceof DefaultValueHolder defaultValueHolder ? defaultValueHolder.defaultValue : result);
 	}
 

spring-core/src/main/java/org/springframework/core/annotation/AnnotationsScanner.java

@@ -127,29 +127,31 @@ private static <C, R> R processClassInheritedAnnotations(C context, Class<?> sou
 				if (result != null) {
 					return result;
 				}
-				Annotation[] declaredAnnotations = getDeclaredAnnotations(source, true);
-				if (relevant == null && declaredAnnotations.length > 0) {
-					relevant = root.getAnnotations();
-					remaining = relevant.length;
-				}
-				for (int i = 0; i < declaredAnnotations.length; i++) {
-					if (declaredAnnotations[i] != null) {
-						boolean isRelevant = false;
-						for (int relevantIndex = 0; relevantIndex < relevant.length; relevantIndex++) {
-							if (relevant[relevantIndex] != null &&
-									declaredAnnotations[i].annotationType() == relevant[relevantIndex].annotationType()) {
-								isRelevant = true;
-								relevant[relevantIndex] = null;
-								remaining--;
-								break;
+				Annotation[] declaredAnns = getDeclaredAnnotations(source, true);
+				if (declaredAnns.length > 0) {
+					if (relevant == null) {
+						relevant = root.getAnnotations();
+						remaining = relevant.length;
+					}
+					for (int i = 0; i < declaredAnns.length; i++) {
+						if (declaredAnns[i] != null) {
+							boolean isRelevant = false;
+							for (int relevantIndex = 0; relevantIndex < relevant.length; relevantIndex++) {
+								if (relevant[relevantIndex] != null &&
+										declaredAnns[i].annotationType() == relevant[relevantIndex].annotationType()) {
+									isRelevant = true;
+									relevant[relevantIndex] = null;
+									remaining--;
+									break;
+								}
+							}
+							if (!isRelevant) {
+								declaredAnns[i] = null;
 							}
-						}
-						if (!isRelevant) {
-							declaredAnnotations[i] = null;
 						}
 					}
 				}
-				result = processor.doWithAnnotations(context, aggregateIndex, source, declaredAnnotations);
+				result = processor.doWithAnnotations(context, aggregateIndex, source, declaredAnns);
 				if (result != null) {
 					return result;
 				}

spring-core/src/main/java/org/springframework/core/annotation/TypeMappedAnnotation.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.
@@ -322,12 +322,13 @@ private <T extends Map<String, Object>> Object adaptValueForMapOptions(Method at
 	@SuppressWarnings("unchecked")
 	protected A createSynthesizedAnnotation() {
 		// Check root annotation
-		if (isTargetAnnotation(this.rootAttributes) && !isSynthesizable((Annotation) this.rootAttributes)) {
-			return (A) this.rootAttributes;
+		if (this.rootAttributes instanceof Annotation ann && isTargetAnnotation(ann) && !isSynthesizable(ann)) {
+			return (A) ann;
 		}
 		// Check meta-annotation
-		else if (isTargetAnnotation(this.mapping.getAnnotation()) && !isSynthesizable(this.mapping.getAnnotation())) {
-			return (A) this.mapping.getAnnotation();
+		Annotation meta = this.mapping.getAnnotation();
+		if (meta != null && isTargetAnnotation(meta) && !isSynthesizable(meta)) {
+			return (A) meta;
 		}
 		return SynthesizedMergedAnnotationInvocationHandler.createProxy(this, getType());
 	}
@@ -338,7 +339,7 @@ else if (isTargetAnnotation(this.mapping.getAnnotation()) && !isSynthesizable(th
 	 * @param obj the object to check
 	 * @since 5.3.22
 	 */
-	private boolean isTargetAnnotation(@Nullable Object obj) {
+	private boolean isTargetAnnotation(Object obj) {
 		return getType().isInstance(obj);
 	}
 
@@ -432,7 +433,7 @@ private Object getValueFromMetaAnnotation(int attributeIndex, boolean forMirrorR
 	}
 
 	@Nullable
-	private Object getValueForMirrorResolution(Method attribute, Object annotation) {
+	private Object getValueForMirrorResolution(Method attribute, @Nullable Object annotation) {
 		int attributeIndex = this.mapping.getAttributes().indexOf(attribute);
 		boolean valueAttribute = VALUE.equals(attribute.getName());
 		return getValue(attributeIndex, !valueAttribute, true);

spring-core/src/main/java/org/springframework/core/codec/Decoder.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.
@@ -95,20 +95,19 @@ default T decode(DataBuffer buffer, ResolvableType targetType,
 			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) throws DecodingException {
 
 		CompletableFuture<T> future = decodeToMono(Mono.just(buffer), targetType, mimeType, hints).toFuture();
-		Assert.state(future.isDone(), "DataBuffer decoding should have completed.");
+		Assert.state(future.isDone(), "DataBuffer decoding should have completed");
 
-		Throwable failure;
 		try {
 			return future.get();
 		}
 		catch (ExecutionException ex) {
-			failure = ex.getCause();
+			Throwable cause = ex.getCause();
+			throw (cause instanceof CodecException codecException ? codecException :
+					new DecodingException("Failed to decode: " + (cause != null ? cause.getMessage() : ex), cause));
 		}
 		catch (InterruptedException ex) {
-			failure = ex;
+			throw new DecodingException("Interrupted during decode", ex);
 		}
-		throw (failure instanceof CodecException codecException ? codecException :
-				new DecodingException("Failed to decode: " + failure.getMessage(), failure));
 	}
 
 	/**

spring-core/src/main/java/org/springframework/core/codec/ResourceDecoder.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.
@@ -80,6 +80,7 @@ public Resource decode(DataBuffer dataBuffer, ResolvableType elementType,
 		if (clazz == InputStreamResource.class) {
 			return new InputStreamResource(new ByteArrayInputStream(bytes)) {
 				@Override
+				@Nullable
 				public String getFilename() {
 					return filename;
 				}
@@ -92,6 +93,7 @@ public long contentLength() {
 		else if (Resource.class.isAssignableFrom(clazz)) {
 			return new ByteArrayResource(bytes) {
 				@Override
+				@Nullable
 				public String getFilename() {
 					return filename;
 				}

spring-core/src/main/java/org/springframework/core/convert/support/ObjectToObjectConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 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.
@@ -136,7 +136,7 @@ static boolean hasConversionMethodOrConstructor(Class<?> targetClass, Class<?> s
 	@Nullable
 	private static Executable getValidatedExecutable(Class<?> targetClass, Class<?> sourceClass) {
 		Executable executable = conversionExecutableCache.get(targetClass);
-		if (isApplicable(executable, sourceClass)) {
+		if (executable != null && isApplicable(executable, sourceClass)) {
 			return executable;
 		}
 

spring-core/src/main/java/org/springframework/core/convert/support/StringToPatternConverter.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.
@@ -19,6 +19,7 @@
 import java.util.regex.Pattern;
 
 import org.springframework.core.convert.converter.Converter;
+import org.springframework.lang.Nullable;
 
 /**
  * Converts from a String to a {@link java.util.regex.Pattern}.
@@ -30,6 +31,7 @@
 final class StringToPatternConverter implements Converter<String, Pattern> {
 
 	@Override
+	@Nullable
 	public Pattern convert(String source) {
 		if (source.isEmpty()) {
 			return null;