GH-2940: Improvements in DefaultKafkaHeaderMapper

Fixes: #2940 

Minor improvements and code cleanup in DefaultKafkaHeaderMapper.

spring-kafka/src/main/java/org/springframework/kafka/support/DefaultKafkaHeaderMapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2022 the original author or authors.
+ * Copyright 2017-2023 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.
@@ -20,8 +20,8 @@ import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
@@ -31,13 +31,13 @@ import org.apache.kafka.common.header.Header;
 import org.apache.kafka.common.header.Headers;
 import org.apache.kafka.common.header.internals.RecordHeader;
 
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.MessageHeaders;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.MimeType;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.DeserializationContext;
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -63,26 +63,23 @@ public class DefaultKafkaHeaderMapper extends AbstractKafkaHeaderMapper {
 
 	private static final String JAVA_LANG_STRING = "java.lang.String";
 
-	private static final Set<String> TRUSTED_ARRAY_TYPES =
-			new HashSet<>(Arrays.asList(
+	private static final Set<String> TRUSTED_ARRAY_TYPES = Set.of(
 					"[B",
 					"[I",
 					"[J",
 					"[F",
 					"[D",
 					"[C"
-			));
+			);
 
-	private static final List<String> DEFAULT_TRUSTED_PACKAGES =
-			Arrays.asList(
+	private static final List<String> DEFAULT_TRUSTED_PACKAGES = List.of(
 					"java.lang",
 					"java.net",
 					"java.util",
 					"org.springframework.util"
 			);
 
-	private static final List<String> DEFAULT_TO_STRING_CLASSES =
-			Arrays.asList(
+	private static final List<String> DEFAULT_TO_STRING_CLASSES = List.of(
 					"org.springframework.util.MimeType",
 					"org.springframework.http.MediaType"
 			);
@@ -142,7 +139,7 @@ public class DefaultKafkaHeaderMapper extends AbstractKafkaHeaderMapper {
 	 * @see org.springframework.util.PatternMatchUtils#simpleMatch(String, String)
 	 */
 	public DefaultKafkaHeaderMapper(String... patterns) {
-		this(new ObjectMapper(), patterns);
+		this(JacksonUtils.enhancedObjectMapper(), patterns);
 	}
 
 	/**
@@ -222,7 +219,7 @@ public class DefaultKafkaHeaderMapper extends AbstractKafkaHeaderMapper {
 	}
 
 	/**
-	 * Set to true to encode String-valued headers as JSON ("..."), by default just the
+	 * Set to true to encode String-valued headers as JSON string ("..."), by default just the
 	 * raw String value is converted to a byte array using the configured charset. Set to
 	 * true if a consumer of the outbound record is using Spring for Apache Kafka version
 	 * less than 2.3
@@ -234,8 +231,15 @@ public class DefaultKafkaHeaderMapper extends AbstractKafkaHeaderMapper {
 	}
 
 	/**
-	 * Add packages to the trusted packages list (default {@code java.util, java.lang}) used
+	 * Add packages to the trusted packages list used
 	 * when constructing objects from JSON.
+	 * By default, the following packages are trusted:
+	 * <ul>
+	 *	<li>java.lang</li>
+	 *  <li>java.net</li>
+	 *  <li>java.util</li>
+	 *  <li>org.springframework.util</li>
+	 * </ul>
 	 * If any of the supplied packages is {@code "*"}, all packages are trusted.
 	 * If a class for a non-trusted package is encountered, the header is returned to the
 	 * application with value of type {@link NonTrustedHeaderType}.
@@ -286,7 +290,6 @@ public class DefaultKafkaHeaderMapper extends AbstractKafkaHeaderMapper {
 						}
 						if (!encodeToJson && valueToAdd instanceof String) {
 							target.add(new RecordHeader(key, ((String) valueToAdd).getBytes(getCharset())));
-							className = JAVA_LANG_STRING;
 						}
 						else {
 							target.add(new RecordHeader(key, headerObjectMapper.writeValueAsBytes(valueToAdd)));
@@ -294,12 +297,12 @@ public class DefaultKafkaHeaderMapper extends AbstractKafkaHeaderMapper {
 						jsonHeaders.put(key, className);
 					}
 					catch (Exception e) {
-						logger.debug(e, () -> "Could not map " + key + " with type " + rawValue.getClass().getName());
+						logger.error(e, () -> "Could not map " + key + " with type " + rawValue.getClass().getName());
 					}
 				}
 			}
 		});
-		if (jsonHeaders.size() > 0) {
+		if (!jsonHeaders.isEmpty()) {
 			try {
 				target.add(new RecordHeader(JSON_TYPES, headerObjectMapper.writeValueAsBytes(jsonHeaders)));
 			}
@@ -321,7 +324,7 @@ public class DefaultKafkaHeaderMapper extends AbstractKafkaHeaderMapper {
 				headers.put(headerName, new String(header.value(), getCharset()));
 			}
 			else if (!(headerName.equals(JSON_TYPES)) && matchesForInbound(headerName)) {
-				if (jsonTypes != null && jsonTypes.containsKey(headerName)) {
+				if (jsonTypes.containsKey(headerName)) {
 					String requestedType = jsonTypes.get(headerName);
 					populateJsonValueHeader(header, requestedType, headers);
 				}
@@ -355,8 +358,7 @@ public class DefaultKafkaHeaderMapper extends AbstractKafkaHeaderMapper {
 				}
 				catch (IOException e) {
 					logger.error(e, () ->
-							"Could not decode json type: " + new String(header.value()) + " for key: "
-									+ header.key());
+							"Could not decode json type: " + requestedType + " for key: " + header.key());
 					headers.put(header.key(), header.value());
 				}
 			}
@@ -385,18 +387,16 @@ public class DefaultKafkaHeaderMapper extends AbstractKafkaHeaderMapper {
 		return value;
 	}
 
-	@SuppressWarnings("unchecked")
-	@Nullable
 	private Map<String, String> decodeJsonTypes(Headers source) {
-		Map<String, String> types = null;
+		Map<String, String> types = Collections.emptyMap();
 		Header jsonTypes = source.lastHeader(JSON_TYPES);
 		if (jsonTypes != null) {
 			ObjectMapper headerObjectMapper = getObjectMapper();
 			try {
-				types = headerObjectMapper.readValue(jsonTypes.value(), Map.class);
+				types = headerObjectMapper.readValue(jsonTypes.value(), new TypeReference<>() { });
 			}
 			catch (IOException e) {
-				logger.error(e, () -> "Could not decode json types: " + new String(jsonTypes.value()));
+				logger.error(e, () -> "Could not decode json types: " + new String(jsonTypes.value(), StandardCharsets.UTF_8));
 			}
 		}
 		return types;