Support virtual threads for Jackson pool.

Author: youssef3wi

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

@@ -31,6 +31,8 @@
 import com.fasterxml.jackson.annotation.JsonAutoDetect;
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.PropertyAccessor;
+import com.fasterxml.jackson.core.JsonFactory;
+import com.fasterxml.jackson.core.util.JsonRecyclerPools;
 import com.fasterxml.jackson.databind.Module;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.PropertyNamingStrategies;
@@ -49,6 +51,7 @@
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.jackson.JacksonProperties.ConstructorDetectorStrategy;
+import org.springframework.boot.autoconfigure.thread.Threading;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.jackson.JsonComponentModule;
 import org.springframework.boot.jackson.JsonMixinModule;
@@ -59,6 +62,7 @@
 import org.springframework.context.annotation.Primary;
 import org.springframework.context.annotation.Scope;
 import org.springframework.core.Ordered;
+import org.springframework.core.env.Environment;
 import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
@@ -127,8 +131,14 @@ static class JacksonObjectMapperConfiguration {
 		@Bean
 		@Primary
 		@ConditionalOnMissingBean
-		ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {
-			return builder.createXmlMapper(false).build();
+		ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder, Environment environment) {
+			builder = builder.createXmlMapper(false);
+			JsonFactory factory = JsonFactory.builder().build();
+			if (Threading.VIRTUAL.isActive(environment)) {
+				factory.setRecyclerPool(JsonRecyclerPools.sharedLockFreePool());
+			}
+
+			return builder.build();
 		}
 
 	}

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jackson/JacksonAutoConfigurationTests.java

@@ -29,9 +29,12 @@
 import com.fasterxml.jackson.annotation.JsonCreator.Mode;
 import com.fasterxml.jackson.annotation.JsonFormat;
 import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.core.JsonFactory;
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.core.ObjectCodec;
+import com.fasterxml.jackson.core.util.JsonRecyclerPools.LockFreePool;
+import com.fasterxml.jackson.core.util.JsonRecyclerPools.ThreadLocalPool;
 import com.fasterxml.jackson.databind.AnnotationIntrospector;
 import com.fasterxml.jackson.databind.DeserializationConfig;
 import com.fasterxml.jackson.databind.DeserializationFeature;
@@ -53,6 +56,8 @@
 import com.fasterxml.jackson.module.paramnames.ParameterNamesModule;
 import org.assertj.core.api.InstanceOfAssertFactories;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledOnJre;
+import org.junit.jupiter.api.condition.JRE;
 
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.predicate.ReflectionHintsPredicates;
@@ -491,6 +496,27 @@ void shouldRegisterPropertyNamingStrategyHints() {
 				"UPPER_CAMEL_CASE", "SNAKE_CASE", "UPPER_SNAKE_CASE", "LOWER_CASE", "KEBAB_CASE", "LOWER_DOT_CASE");
 	}
 
+	@Test
+	void shouldUseThreadLocalPool() {
+		this.contextRunner.withPropertyValues("spring.threads.virtual.enabled:false").run((context) -> {
+			ObjectMapper mapper = context.getBean(ObjectMapper.class);
+			assertThat(mapper).extracting(ObjectMapper::getFactory)
+				.extracting(JsonFactory::_getRecyclerPool)
+				.isInstanceOf(ThreadLocalPool.class);
+		});
+	}
+
+	@Test
+	@EnabledOnJre(JRE.JAVA_21)
+	void shouldUseVirtualThread() {
+		this.contextRunner.withPropertyValues("spring.threads.virtual.enabled:true").run((context) -> {
+			ObjectMapper mapper = context.getBean(ObjectMapper.class);
+			assertThat(mapper).extracting(ObjectMapper::getFactory)
+				.extracting(JsonFactory::_getRecyclerPool)
+				.isInstanceOf(LockFreePool.class);
+		});
+	}
+
 	private void shouldRegisterPropertyNamingStrategyHints(Class<?> type, String... fieldNames) {
 		RuntimeHints hints = new RuntimeHints();
 		new JacksonAutoConfigurationRuntimeHints().registerHints(hints, getClass().getClassLoader());