Restore previous serialization formatting in Actuator responses

Fixes gh-33236

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/endpoint/jackson/JacksonEndpointAutoConfiguration.java

@@ -16,7 +16,9 @@
 
 package org.springframework.boot.actuate.autoconfigure.endpoint.jackson;
 
+import com.fasterxml.jackson.annotation.JsonInclude.Include;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
 
 import org.springframework.boot.actuate.endpoint.jackson.EndpointObjectMapper;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
@@ -42,7 +44,10 @@ public class JacksonEndpointAutoConfiguration {
 	@ConditionalOnProperty(name = "management.endpoints.jackson.isolated-object-mapper", matchIfMissing = true)
 	@ConditionalOnClass({ ObjectMapper.class, Jackson2ObjectMapperBuilder.class })
 	public EndpointObjectMapper endpointObjectMapper() {
-		ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json().build();
+		ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json()
+				.featuresToDisable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS,
+						SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS)
+				.serializationInclusion(Include.NON_NULL).build();
 		return () -> objectMapper;
 	}
 

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/endpoint/jackson/JacksonEndpointAutoConfigurationTests.java

@@ -16,6 +16,12 @@
 
 package org.springframework.boot.actuate.autoconfigure.endpoint.jackson;
 
+import java.time.Duration;
+import java.time.Instant;
+import java.time.format.DateTimeFormatter;
+import java.util.HashMap;
+import java.util.Map;
+
 import com.fasterxml.jackson.databind.ObjectMapper;
 import org.junit.jupiter.api.Test;
 
@@ -54,6 +60,37 @@ class JacksonEndpointAutoConfigurationTests {
 				.run((context) -> assertThat(context).doesNotHaveBean(EndpointObjectMapper.class));
 	}
 
+	@Test
+	void endpointObjectMapperDoesNotSerializeDatesAsTimestamps() {
+		this.runner.run((context) -> {
+			ObjectMapper objectMapper = context.getBean(EndpointObjectMapper.class).get();
+			Instant now = Instant.now();
+			String json = objectMapper.writeValueAsString(Map.of("timestamp", now));
+			assertThat(json).contains(DateTimeFormatter.ISO_INSTANT.format(now));
+		});
+	}
+
+	@Test
+	void endpointObjectMapperDoesNotSerializeDurationsAsTimestamps() {
+		this.runner.run((context) -> {
+			ObjectMapper objectMapper = context.getBean(EndpointObjectMapper.class).get();
+			Duration duration = Duration.ofSeconds(42);
+			String json = objectMapper.writeValueAsString(Map.of("duration", duration));
+			assertThat(json).contains(duration.toString());
+		});
+	}
+
+	@Test
+	void endpointObjectMapperDoesNotSerializeNullValues() {
+		this.runner.run((context) -> {
+			ObjectMapper objectMapper = context.getBean(EndpointObjectMapper.class).get();
+			HashMap<String, String> map = new HashMap<>();
+			map.put("key", null);
+			String json = objectMapper.writeValueAsString(map);
+			assertThat(json).isEqualTo("{}");
+		});
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class TestEndpointMapperConfiguration {
 

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/endpoint/web/documentation/AbstractEndpointDocumentationTests.java

@@ -26,10 +26,14 @@ import java.util.stream.Stream;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationFeature;
 
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.config.BeanPostProcessor;
 import org.springframework.boot.actuate.autoconfigure.endpoint.EndpointAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.endpoint.jackson.JacksonEndpointAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.endpoint.web.WebEndpointAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.endpoint.web.reactive.WebFluxEndpointManagementContextConfiguration;
 import org.springframework.boot.actuate.autoconfigure.endpoint.web.servlet.WebMvcEndpointManagementContextConfiguration;
+import org.springframework.boot.actuate.endpoint.jackson.EndpointObjectMapper;
 import org.springframework.boot.autoconfigure.ImportAutoConfiguration;
 import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
 import org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration;
@@ -38,6 +42,7 @@ import org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfig
 import org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.restdocs.operation.preprocess.ContentModifyingOperationPreprocessor;
 import org.springframework.restdocs.operation.preprocess.OperationPreprocessor;
@@ -54,8 +59,7 @@ import static org.springframework.restdocs.payload.PayloadDocumentation.fieldWit
  *
  * @author Andy Wilkinson
  */
-@TestPropertySource(properties = { "spring.jackson.serialization.indent_output=true",
+@TestPropertySource(properties = { "management.endpoints.web.exposure.include=*" })
-		"management.endpoints.web.exposure.include=*", "spring.jackson.default-property-inclusion=non_null" })
 public abstract class AbstractEndpointDocumentationTests {
 
 	protected static String describeEnumValues(Class<? extends Enum<?>> enumType) {
@@ -119,9 +123,26 @@ public abstract class AbstractEndpointDocumentationTests {
 			WebMvcAutoConfiguration.class, DispatcherServletAutoConfiguration.class, EndpointAutoConfiguration.class,
 			WebEndpointAutoConfiguration.class, WebMvcEndpointManagementContextConfiguration.class,
 			WebFluxEndpointManagementContextConfiguration.class, PropertyPlaceholderAutoConfiguration.class,
-			WebFluxAutoConfiguration.class, HttpHandlerAutoConfiguration.class })
+			WebFluxAutoConfiguration.class, HttpHandlerAutoConfiguration.class,
+			JacksonEndpointAutoConfiguration.class })
 	static class BaseDocumentationConfiguration {
 
+		@Bean
+		static BeanPostProcessor endpointObjectMapperBeanPostProcessor() {
+			return new BeanPostProcessor() {
+
+				@Override
+				public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
+					if (bean instanceof EndpointObjectMapper) {
+						return (EndpointObjectMapper) () -> ((EndpointObjectMapper) bean).get()
+								.enable(SerializationFeature.INDENT_OUTPUT);
+					}
+					return bean;
+				}
+
+			};
+		}
+
 	}
 
 }