jspecify nullability changes in support package

serializer and mapping packages under support.

#3762

Signed-off-by: Soby Chacko <[email protected]>

Author: sobychacko

spring-kafka/src/main/java/org/springframework/kafka/support/mapping/AbstractJavaTypeMapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2021 the original author or authors.
+ * Copyright 2017-2025 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.
@@ -24,6 +24,7 @@
 import org.apache.kafka.common.header.Header;
 import org.apache.kafka.common.header.Headers;
 import org.apache.kafka.common.header.internals.RecordHeader;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.messaging.converter.MessageConversionException;
@@ -82,7 +83,7 @@ public abstract class AbstractJavaTypeMapper implements BeanClassLoaderAware {
 
 	private String keyClassIdFieldName = DEFAULT_KEY_CLASSID_FIELD_NAME;
 
-	private ClassLoader classLoader = ClassUtils.getDefaultClassLoader();
+	private @Nullable ClassLoader classLoader = ClassUtils.getDefaultClassLoader();
 
 	public String getClassIdFieldName() {
 		return this.classIdFieldName;
@@ -133,7 +134,7 @@ public void setBeanClassLoader(ClassLoader classLoader) {
 		this.classLoader = classLoader;
 	}
 
-	protected ClassLoader getClassLoader() {
+	protected @Nullable ClassLoader getClassLoader() {
 		return this.classLoader;
 	}
 
@@ -155,7 +156,7 @@ protected String retrieveHeader(Headers headers, String headerName) {
 		return classId;
 	}
 
-	protected String retrieveHeaderAsString(Headers headers, String headerName) {
+	protected @Nullable String retrieveHeaderAsString(Headers headers, String headerName) {
 		Header header = headers.lastHeader(headerName);
 		if (header != null) {
 			String classId = null;

spring-kafka/src/main/java/org/springframework/kafka/support/mapping/ClassMapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2021 the original author or authors.
+ * Copyright 2017-2025 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.
@@ -17,6 +17,7 @@
 package org.springframework.kafka.support.mapping;
 
 import org.apache.kafka.common.header.Headers;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Strategy for setting metadata on messages such that one can create the class
@@ -32,6 +33,7 @@ public interface ClassMapper {
 
 	void fromClass(Class<?> clazz, Headers headers);
 
+	@Nullable
 	Class<?> toClass(Headers headers);
 
 }

spring-kafka/src/main/java/org/springframework/kafka/support/mapping/DefaultJackson2JavaTypeMapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2024 the original author or authors.
+ * Copyright 2017-2025 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.
@@ -23,6 +23,7 @@
 import com.fasterxml.jackson.databind.JavaType;
 import com.fasterxml.jackson.databind.type.TypeFactory;
 import org.apache.kafka.common.header.Headers;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.messaging.converter.MessageConversionException;
 import org.springframework.util.Assert;
@@ -89,7 +90,7 @@ public void addTrustedPackages(String... packagesToTrust) {
 	}
 
 	@Override
-	public JavaType toJavaType(Headers headers) {
+	public @Nullable JavaType toJavaType(Headers headers) {
 		String typeIdHeader = retrieveHeaderAsString(headers, getClassIdFieldName());
 
 		if (typeIdHeader != null) {
@@ -181,8 +182,9 @@ public void fromClass(Class<?> clazz, Headers headers) {
 	}
 
 	@Override
-	public Class<?> toClass(Headers headers) {
-		return toJavaType(headers).getRawClass();
+	public @Nullable Class<?> toClass(Headers headers) {
+		JavaType javaType = toJavaType(headers);
+		return javaType == null ? null : javaType.getRawClass();
 	}
 
 	@Override

spring-kafka/src/main/java/org/springframework/kafka/support/mapping/Jackson2JavaTypeMapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2024 the original author or authors.
+ * Copyright 2017-2025 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.
@@ -18,6 +18,7 @@
 
 import com.fasterxml.jackson.databind.JavaType;
 import org.apache.kafka.common.header.Headers;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Strategy for setting metadata on messages such that one can create the class that needs
@@ -52,6 +53,7 @@ enum TypePrecedence {
 
 	void fromJavaType(JavaType javaType, Headers headers);
 
+	@Nullable
 	JavaType toJavaType(Headers headers);
 
 	TypePrecedence getTypePrecedence();

spring-kafka/src/main/java/org/springframework/kafka/support/mapping/package-info.java

@@ -1,4 +1,5 @@
 /**
  * Provides classes related to type mapping.
  */
-package org.springframework.kafka.support.mapping;
+@org.jspecify.annotations.NullMarked
+package org.springframework.kafka.support.mapping;

spring-kafka/src/main/java/org/springframework/kafka/support/serializer/DelegatingByTopicSerialization.java

@@ -84,7 +84,7 @@ public abstract class DelegatingByTopicSerialization<T extends Closeable> implem
 
 	private final Set<String> patterns = ConcurrentHashMap.newKeySet();
 
-	private T defaultDelegate;
+	private @Nullable T defaultDelegate;
 
 	private boolean forKeys;
 
@@ -93,7 +93,7 @@ public abstract class DelegatingByTopicSerialization<T extends Closeable> implem
 	public DelegatingByTopicSerialization() {
 	}
 
-	public DelegatingByTopicSerialization(Map<Pattern, T> delegates, T defaultDelegate) {
+	public DelegatingByTopicSerialization(Map<Pattern, T> delegates, @Nullable T defaultDelegate) {
 		Assert.notNull(delegates, "'delegates' cannot be null");
 		Assert.notNull(defaultDelegate, "'defaultDelegate' cannot be null");
 		this.delegates.putAll(delegates);
@@ -260,7 +260,7 @@ else if (key instanceof String regex) {
 		}
 	}
 
-	protected T instantiateAndConfigure(Map<String, ?> configs, boolean isKey, Map<Pattern, T> delegates2,
+	protected @Nullable T instantiateAndConfigure(Map<String, ?> configs, boolean isKey, Map<Pattern, T> delegates2,
 			@Nullable Pattern pattern, Class<?> clazz) {
 
 		if (pattern != null && !this.patterns.add(pattern.pattern())) {

spring-kafka/src/main/java/org/springframework/kafka/support/serializer/DelegatingByTopicSerializer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019-2022 the original author or authors.
+ * Copyright 2019-2025 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.
@@ -71,7 +71,7 @@ public byte[] serialize(String topic, Object data) {
 		throw new UnsupportedOperationException();
 	}
 
-	@SuppressWarnings("unchecked")
+	@SuppressWarnings({"unchecked", "NullAway"}) // Dataflow analysis limitation
 	@Override
 	public byte[] serialize(String topic, Headers headers, Object data) {
 		if (data == null) {

spring-kafka/src/main/java/org/springframework/kafka/support/serializer/DelegatingByTypeSerializer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2021-2024 the original author or authors.
+ * Copyright 2021-2025 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.
@@ -81,6 +81,7 @@ public void configure(Map<String, ?> configs, boolean isKey) {
 		this.delegates.values().forEach(del -> del.configure(configs, isKey));
 	}
 
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	@Override
 	public byte[] serialize(String topic, Object data) {
 		if (data == null) {
@@ -90,6 +91,7 @@ public byte[] serialize(String topic, Object data) {
 		return delegate.serialize(topic, data);
 	}
 
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	@Override
 	public byte[] serialize(String topic, Headers headers, Object data) {
 		if (data == null) {

spring-kafka/src/main/java/org/springframework/kafka/support/serializer/DelegatingDeserializer.java

@@ -178,7 +178,7 @@ public Object deserialize(String topic, Headers headers, ByteBuffer data) {
 		return deserializer == null ? data : deserializer.deserialize(topic, headers, data);
 	}
 
-	private Deserializer<?> getDeserializerByHeaders(Headers headers) {
+	private @Nullable Deserializer<?> getDeserializerByHeaders(Headers headers) {
 		byte[] value = null;
 		String selectorKey = selectorKey();
 		Header header = headers.lastHeader(selectorKey);

spring-kafka/src/main/java/org/springframework/kafka/support/serializer/DelegatingSerializer.java

@@ -187,6 +187,7 @@ public byte[] serialize(String topic, Object data) {
 		throw new UnsupportedOperationException();
 	}
 
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	@Override
 	public byte[] serialize(String topic, Headers headers, Object data) {
 		if (data == null) {
@@ -229,7 +230,7 @@ private String selectorKey() {
 	/*
 	 * Package for testing.
 	 */
-	@Nullable
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	byte[] trySerdes(Object data) {
 		try {
 			Serde<? extends Object> serdeFrom = Serdes.serdeFrom(data.getClass());