Add nullSafeValue method that accepts a mapper Function

Update `JsonObjectDeserializer` with a `nullSafeValue` method that
accepts a mapper `Function`

Closes gh-42972

Author: philwebb

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/json/JsonTestIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -16,6 +16,9 @@
 
 package org.springframework.boot.test.autoconfigure.json;
 
+import java.util.Date;
+import java.util.UUID;
+
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.annotation.Autowired;
@@ -75,7 +78,7 @@ void jacksonBasic() throws Exception {
 
 	@Test
 	void jacksonCustom() throws Exception {
-		ExampleCustomObject object = new ExampleCustomObject("spring");
+		ExampleCustomObject object = new ExampleCustomObject("spring", new Date(), UUID.randomUUID());
 		assertThat(this.jacksonCustomJson.write(object)).isEqualToJson("example.json");
 	}
 

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/json/app/ExampleCustomObject.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -16,35 +16,17 @@
 
 package org.springframework.boot.test.autoconfigure.json.app;
 
+import java.util.Date;
+import java.util.UUID;
+
 /**
  * Example object to read/write as JSON through {@link ExampleJsonComponent}.
  *
  * @author Phillip Webb
+ * @param value the value
+ * @param date a date
+ * @param uuid a uuid
  */
-public class ExampleCustomObject {
-
-	private final String value;
-
-	public ExampleCustomObject(String value) {
-		this.value = value;
-	}
-
-	@Override
-	public boolean equals(Object obj) {
-		if (obj != null && obj.getClass() == getClass()) {
-			return this.value.equals(((ExampleCustomObject) obj).value);
-		}
-		return false;
-	}
-
-	@Override
-	public int hashCode() {
-		return this.value.hashCode();
-	}
-
-	@Override
-	public String toString() {
-		return this.value;
-	}
+public record ExampleCustomObject(String value, Date date, UUID uuid) {
 
 }

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/json/app/ExampleJsonComponent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -17,6 +17,8 @@
 package org.springframework.boot.test.autoconfigure.json.app;
 
 import java.io.IOException;
+import java.util.Date;
+import java.util.UUID;
 
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.core.JsonParser;
@@ -44,7 +46,9 @@ static class Serializer extends JsonObjectSerializer<ExampleCustomObject> {
 		@Override
 		protected void serializeObject(ExampleCustomObject value, JsonGenerator jgen, SerializerProvider provider)
 				throws IOException {
-			jgen.writeStringField("value", value.toString());
+			jgen.writeStringField("value", value.value());
+			jgen.writeNumberField("date", value.date().getTime());
+			jgen.writeStringField("uuid", value.uuid().toString());
 		}
 
 	}
@@ -54,7 +58,10 @@ static class Deserializer extends JsonObjectDeserializer<ExampleCustomObject> {
 		@Override
 		protected ExampleCustomObject deserializeObject(JsonParser jsonParser, DeserializationContext context,
 				ObjectCodec codec, JsonNode tree) throws IOException {
-			return new ExampleCustomObject(nullSafeValue(tree.get("value"), String.class));
+			String value = nullSafeValue(tree.get("value"), String.class);
+			Date date = nullSafeValue(tree.get("date"), Integer.class, Date::new);
+			UUID uuid = nullSafeValue(tree.get("uuid"), String.class, UUID::fromString);
+			return new ExampleCustomObject(value, date, uuid);
 		}
 
 	}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/jackson/JsonObjectDeserializer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2024 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.io.IOException;
 import java.math.BigDecimal;
 import java.math.BigInteger;
+import java.util.function.Function;
 
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.core.ObjectCodec;
@@ -72,6 +73,24 @@ public final T deserialize(JsonParser jp, DeserializationContext ctxt) throws IO
 	protected abstract T deserializeObject(JsonParser jsonParser, DeserializationContext context, ObjectCodec codec,
 			JsonNode tree) throws IOException;
 
+	/**
+	 * Helper method to extract a value from the given {@code jsonNode} or return
+	 * {@code null} when the node itself is {@code null}.
+	 * @param jsonNode the source node (may be {@code null})
+	 * @param type the data type. May be {@link String}, {@link Boolean}, {@link Long},
+	 * {@link Integer}, {@link Short}, {@link Double}, {@link Float}, {@link BigDecimal}
+	 * or {@link BigInteger}.
+	 * @param <D> the data type requested
+	 * @param <R> the result type
+	 * @param mapper a mapper to convert the value when it is not {@code null}
+	 * @return the node value or {@code null}
+	 * @since 3.4.0
+	 */
+	protected final <D, R> R nullSafeValue(JsonNode jsonNode, Class<D> type, Function<D, R> mapper) {
+		D value = nullSafeValue(jsonNode, type);
+		return (value != null) ? mapper.apply(value) : null;
+	}
+
 	/**
 	 * Helper method to extract a value from the given {@code jsonNode} or return
 	 * {@code null} when the node itself is {@code null}.