Nullability refinements and related polishing

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

@@ -77,14 +77,13 @@ public abstract class KotlinDetector {
 
 	/**
 	 * Return {@code true} if the method is a suspending function.
-	 *
 	 * @author Sebastien Deleuze
 	 * @since 5.3
 	 */
 	public static boolean isSuspendingFunction(Method method) {
 		if (KotlinDetector.isKotlinType(method.getDeclaringClass())) {
 			Class<?>[] types = method.getParameterTypes();
-			if ((types.length > 0) && "kotlin.coroutines.Continuation".equals(types[types.length - 1].getName())) {
+			if (types.length > 0 && "kotlin.coroutines.Continuation".equals(types[types.length - 1].getName())) {
 				return true;
 			}
 		}

spring-test/src/main/java/org/springframework/test/context/support/ContextLoaderUtils.java

@@ -27,6 +27,7 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
 import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.lang.Nullable;
 import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.ContextConfigurationAttributes;
 import org.springframework.test.context.ContextHierarchy;
@@ -249,11 +250,11 @@ abstract class ContextLoaderUtils {
 	}
 
 	private static void resolveContextConfigurationAttributes(List<ContextConfigurationAttributes> attributesList,
-			AnnotationDescriptor<ContextConfiguration> descriptor) {
+			@Nullable AnnotationDescriptor<ContextConfiguration> descriptor) {
 
 		if (descriptor != null) {
 			convertContextConfigToConfigAttributesAndAddToList(descriptor.synthesizeAnnotation(),
-				descriptor.getRootDeclaringClass(), attributesList);
+					descriptor.getRootDeclaringClass(), attributesList);
 			resolveContextConfigurationAttributes(attributesList, descriptor.next());
 		}
 	}

spring-test/src/main/java/org/springframework/test/context/transaction/TransactionalTestExecutionListener.java

@@ -163,6 +163,7 @@ public class TransactionalTestExecutionListener extends AbstractTestExecutionLis
 			return findTransactionAttributeInEnclosingClassHierarchy(clazz);
 		}
 
+		@Nullable
 		private TransactionAttribute findTransactionAttributeInEnclosingClassHierarchy(Class<?> clazz) {
 			if (MetaAnnotationUtils.searchEnclosingClass(clazz)) {
 				return findTransactionAttribute(clazz.getEnclosingClass());

spring-test/src/main/java/org/springframework/test/context/web/WebTestContextBootstrapper.java

@@ -16,6 +16,7 @@
 
 package org.springframework.test.context.web;
 
+import org.springframework.lang.Nullable;
 import org.springframework.test.context.ContextLoader;
 import org.springframework.test.context.MergedContextConfiguration;
 import org.springframework.test.context.TestContextBootstrapper;
@@ -70,6 +71,7 @@ public class WebTestContextBootstrapper extends DefaultTestContextBootstrapper {
 		}
 	}
 
+	@Nullable
 	private static WebAppConfiguration getWebAppConfiguration(Class<?> testClass) {
 		return MetaAnnotationUtils.findMergedAnnotation(testClass, WebAppConfiguration.class);
 	}

spring-web/src/main/java/org/springframework/http/codec/json/KotlinSerializationJsonDecoder.java

@@ -31,6 +31,7 @@ import org.springframework.core.codec.AbstractDecoder;
 import org.springframework.core.codec.StringDecoder;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.http.MediaType;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ConcurrentReferenceHashMap;
 import org.springframework.util.MimeType;
 
@@ -58,6 +59,7 @@ public class KotlinSerializationJsonDecoder extends AbstractDecoder<Object> {
 	// String decoding needed for now, see https://github.com/Kotlin/kotlinx.serialization/issues/204 for more details
 	private final StringDecoder stringDecoder = StringDecoder.allMimeTypes(StringDecoder.DEFAULT_DELIMITERS, false);
 
+
 	public KotlinSerializationJsonDecoder() {
 		this(Json.Default);
 	}
@@ -67,18 +69,23 @@ public class KotlinSerializationJsonDecoder extends AbstractDecoder<Object> {
 		this.json = json;
 	}
 
+
 	@Override
-	public boolean canDecode(ResolvableType elementType, MimeType mimeType) {
+	public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType) {
-		return super.canDecode(elementType, mimeType) && (!CharSequence.class.isAssignableFrom(elementType.toClass()));
+		return (super.canDecode(elementType, mimeType) && !CharSequence.class.isAssignableFrom(elementType.toClass()));
 	}
 
 	@Override
-	public Flux<Object> decode(Publisher<DataBuffer> inputStream, ResolvableType elementType, MimeType mimeType, Map<String, Object> hints) {
+	public Flux<Object> decode(Publisher<DataBuffer> inputStream, ResolvableType elementType,
+			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
+
 		return Flux.error(new UnsupportedOperationException());
 	}
 
 	@Override
-	public Mono<Object> decodeToMono(Publisher<DataBuffer> inputStream, ResolvableType elementType, MimeType mimeType, Map<String, Object> hints) {
+	public Mono<Object> decodeToMono(Publisher<DataBuffer> inputStream, ResolvableType elementType,
+			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
+
 		return this.stringDecoder
 				.decodeToMono(inputStream, elementType, mimeType, hints)
 				.map(jsonText -> this.json.decodeFromString(serializer(elementType.getType()), jsonText));
@@ -100,4 +107,5 @@ public class KotlinSerializationJsonDecoder extends AbstractDecoder<Object> {
 		}
 		return serializer;
 	}
+
 }

spring-web/src/main/java/org/springframework/http/codec/json/KotlinSerializationJsonEncoder.java

@@ -34,6 +34,7 @@ import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.ServerSentEvent;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ConcurrentReferenceHashMap;
 import org.springframework.util.MimeType;
 
@@ -57,6 +58,7 @@ public class KotlinSerializationJsonEncoder extends AbstractEncoder<Object> {
 	// CharSequence encoding needed for now, see https://github.com/Kotlin/kotlinx.serialization/issues/204 for more details
 	private final CharSequenceEncoder charSequenceEncoder = CharSequenceEncoder.allMimeTypes();
 
+
 	public KotlinSerializationJsonEncoder() {
 		this(Json.Default);
 	}
@@ -66,15 +68,17 @@ public class KotlinSerializationJsonEncoder extends AbstractEncoder<Object> {
 		this.json = json;
 	}
 
+
 	@Override
-	public boolean canEncode(ResolvableType elementType, MimeType mimeType) {
+	public boolean canEncode(ResolvableType elementType, @Nullable MimeType mimeType) {
-		return super.canEncode(elementType, mimeType)
+		return (super.canEncode(elementType, mimeType) && !String.class.isAssignableFrom(elementType.toClass()) &&
-				&& (!String.class.isAssignableFrom(elementType.toClass()))
+				!ServerSentEvent.class.isAssignableFrom(elementType.toClass()));
-				&& (!ServerSentEvent.class.isAssignableFrom(elementType.toClass()));
 	}
 
 	@Override
-	public Flux<DataBuffer> encode(Publisher<?> inputStream, DataBufferFactory bufferFactory, ResolvableType elementType, MimeType mimeType, Map<String, Object> hints) {
+	public Flux<DataBuffer> encode(Publisher<?> inputStream, DataBufferFactory bufferFactory,
+			ResolvableType elementType, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
+
 		if (inputStream instanceof Mono) {
 			return Mono.from(inputStream)
 					.map(value -> encodeValue(value, bufferFactory, elementType, mimeType, hints))
@@ -90,7 +94,9 @@ public class KotlinSerializationJsonEncoder extends AbstractEncoder<Object> {
 	}
 
 	@Override
-	public DataBuffer encodeValue(Object value, DataBufferFactory bufferFactory, ResolvableType valueType, MimeType mimeType, Map<String, Object> hints) {
+	public DataBuffer encodeValue(Object value, DataBufferFactory bufferFactory,
+			ResolvableType valueType, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
+
 		String json = this.json.encodeToString(serializer(valueType.getType()), value);
 		return this.charSequenceEncoder.encodeValue(json, bufferFactory, valueType, mimeType, null);
 	}
@@ -111,4 +117,5 @@ public class KotlinSerializationJsonEncoder extends AbstractEncoder<Object> {
 		}
 		return serializer;
 	}
+
 }

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ContinuationHandlerMethodArgumentResolver.java

@@ -17,6 +17,7 @@
 package org.springframework.web.servlet.mvc.method.annotation;
 
 import org.springframework.core.MethodParameter;
+import org.springframework.lang.Nullable;
 import org.springframework.web.bind.support.WebDataBinderFactory;
 import org.springframework.web.context.request.NativeWebRequest;
 import org.springframework.web.method.support.HandlerMethodArgumentResolver;
@@ -36,7 +37,10 @@ public class ContinuationHandlerMethodArgumentResolver implements HandlerMethodA
 	}
 
 	@Override
-	public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
+	public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
+			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
+
 		return null;
 	}
+
 }