Support isolated actuator ObjectMapper

Add `OperationResponseBody` tagging interface that can be used
to trigger the use of an isolated ObjectMapper specifically for
actuator responses.

The isolated mapper is provided by an `EndpointObjectMapper`
bean which is auto-configured unless specifically disabled
by the user.

WebMVC, WebFlux and Jersey integrations have been updated
to provide a link between the `OperationResponseBody` type
and the endpoint `ObjectMapper`.

See gh-20291

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

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.endpoint.jackson;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import org.springframework.boot.actuate.endpoint.jackson.EndpointObjectMapper;
+import org.springframework.boot.autoconfigure.AutoConfigureAfter;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
+
+/**
+ * {@link EnableAutoConfiguration Auto-configuration} for Endpoint Jackson support.
+ *
+ * @author Phillip Webb
+ * @since 3.0.0
+ */
+@Configuration(proxyBeanMethods = false)
+@AutoConfigureAfter(JacksonAutoConfiguration.class)
+public class JacksonEndpointAutoConfiguration {
+
+	@Bean
+	@ConditionalOnProperty(name = "management.endpoints.jackson.isolated-object-mapper", matchIfMissing = true)
+	@ConditionalOnClass({ ObjectMapper.class, Jackson2ObjectMapperBuilder.class })
+	public EndpointObjectMapper endpointObjectMapper() {
+		ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json().build();
+		return () -> objectMapper;
+	}
+
+}

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

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Actuator Jackson auto-configuration.
+ */
+package org.springframework.boot.actuate.autoconfigure.endpoint.jackson;

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/endpoint/web/jersey/JerseyWebEndpointManagementContextConfiguration.java

@@ -23,6 +23,10 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Objects;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+import jakarta.annotation.Priority;
+import jakarta.ws.rs.Priorities;
+import jakarta.ws.rs.ext.ContextResolver;
 import org.glassfish.jersey.server.ResourceConfig;
 import org.glassfish.jersey.server.model.Resource;
 
@@ -35,7 +39,9 @@ import org.springframework.boot.actuate.autoconfigure.web.server.ConditionalOnMa
 import org.springframework.boot.actuate.autoconfigure.web.server.ManagementPortType;
 import org.springframework.boot.actuate.endpoint.EndpointId;
 import org.springframework.boot.actuate.endpoint.ExposableEndpoint;
+import org.springframework.boot.actuate.endpoint.OperationResponseBody;
 import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
+import org.springframework.boot.actuate.endpoint.jackson.EndpointObjectMapper;
 import org.springframework.boot.actuate.endpoint.web.EndpointLinksResolver;
 import org.springframework.boot.actuate.endpoint.web.EndpointMapping;
 import org.springframework.boot.actuate.endpoint.web.EndpointMediaTypes;
@@ -53,6 +59,7 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
+import org.springframework.boot.autoconfigure.jersey.ResourceConfigCustomizer;
 import org.springframework.context.annotation.Bean;
 import org.springframework.core.env.Environment;
 import org.springframework.util.StringUtils;
@@ -98,6 +105,13 @@ class JerseyWebEndpointManagementContextConfiguration {
 		return new JerseyAdditionalHealthEndpointPathsManagementResourcesRegistrar(health, healthEndpointGroups);
 	}
 
+	@Bean
+	@ConditionalOnBean(EndpointObjectMapper.class)
+	ResourceConfigCustomizer endpointObjectMapperResourceConfigCustomizer(EndpointObjectMapper endpointObjectMapper) {
+		return (config) -> config.register(new EndpointObjectMapperContextResolver(endpointObjectMapper),
+				ContextResolver.class);
+	}
+
 	private boolean shouldRegisterLinksMapping(WebEndpointProperties properties, Environment environment,
 			String basePath) {
 		return properties.getDiscovery().isEnabled() && (StringUtils.hasText(basePath)
@@ -192,4 +206,24 @@ class JerseyWebEndpointManagementContextConfiguration {
 
 	}
 
+	/**
+	 * {@link ContextResolver} used to obtain the {@link ObjectMapper} that should be used
+	 * for {@link OperationResponseBody} instances.
+	 */
+	@Priority(Priorities.USER - 100)
+	private static final class EndpointObjectMapperContextResolver implements ContextResolver<ObjectMapper> {
+
+		private final EndpointObjectMapper endpointObjectMapper;
+
+		private EndpointObjectMapperContextResolver(EndpointObjectMapper endpointObjectMapper) {
+			this.endpointObjectMapper = endpointObjectMapper;
+		}
+
+		@Override
+		public ObjectMapper getContext(Class<?> type) {
+			return OperationResponseBody.class.isAssignableFrom(type) ? this.endpointObjectMapper.get() : null;
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/endpoint/web/reactive/WebFluxEndpointManagementContextConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -17,9 +17,16 @@
 package org.springframework.boot.actuate.autoconfigure.endpoint.web.reactive;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.BeanPostProcessor;
 import org.springframework.boot.actuate.autoconfigure.endpoint.condition.ConditionalOnAvailableEndpoint;
 import org.springframework.boot.actuate.autoconfigure.endpoint.expose.EndpointExposure;
 import org.springframework.boot.actuate.autoconfigure.endpoint.web.CorsEndpointProperties;
@@ -28,7 +35,9 @@ import org.springframework.boot.actuate.autoconfigure.web.ManagementContextConfi
 import org.springframework.boot.actuate.autoconfigure.web.server.ConditionalOnManagementPort;
 import org.springframework.boot.actuate.autoconfigure.web.server.ManagementPortType;
 import org.springframework.boot.actuate.endpoint.ExposableEndpoint;
+import org.springframework.boot.actuate.endpoint.OperationResponseBody;
 import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
+import org.springframework.boot.actuate.endpoint.jackson.EndpointObjectMapper;
 import org.springframework.boot.actuate.endpoint.web.EndpointLinksResolver;
 import org.springframework.boot.actuate.endpoint.web.EndpointMapping;
 import org.springframework.boot.actuate.endpoint.web.EndpointMediaTypes;
@@ -48,7 +57,14 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplicat
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Role;
+import org.springframework.core.codec.Encoder;
 import org.springframework.core.env.Environment;
+import org.springframework.http.MediaType;
+import org.springframework.http.codec.EncoderHttpMessageWriter;
+import org.springframework.http.codec.HttpMessageWriter;
+import org.springframework.http.codec.ServerCodecConfigurer;
+import org.springframework.http.codec.json.Jackson2JsonEncoder;
 import org.springframework.http.server.reactive.HttpHandler;
 import org.springframework.util.StringUtils;
 import org.springframework.web.reactive.DispatcherHandler;
@@ -114,4 +130,55 @@ public class WebFluxEndpointManagementContextConfiguration {
 				corsProperties.toCorsConfiguration());
 	}
 
+	@Bean
+	@ConditionalOnBean(EndpointObjectMapper.class)
+	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
+	static ServerCodecConfigurerEndpointObjectMapperBeanPostProcessor serverCodecConfigurerEndpointObjectMapperBeanPostProcessor(
+			EndpointObjectMapper endpointObjectMapper) {
+		return new ServerCodecConfigurerEndpointObjectMapperBeanPostProcessor(endpointObjectMapper);
+	}
+
+	/**
+	 * {@link BeanPostProcessor} to apply {@link EndpointObjectMapper} for
+	 * {@link OperationResponseBody} to {@link Jackson2JsonEncoder} instances.
+	 */
+	private static class ServerCodecConfigurerEndpointObjectMapperBeanPostProcessor implements BeanPostProcessor {
+
+		private static final List<MediaType> MEDIA_TYPES = Collections
+				.unmodifiableList(Arrays.asList(MediaType.APPLICATION_JSON, new MediaType("application", "*+json")));
+
+		private final EndpointObjectMapper endpointObjectMapper;
+
+		ServerCodecConfigurerEndpointObjectMapperBeanPostProcessor(EndpointObjectMapper endpointObjectMapper) {
+			this.endpointObjectMapper = endpointObjectMapper;
+		}
+
+		@Override
+		public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
+			if (bean instanceof ServerCodecConfigurer) {
+				process((ServerCodecConfigurer) bean);
+			}
+			return bean;
+		}
+
+		private void process(ServerCodecConfigurer configurer) {
+			for (HttpMessageWriter<?> writer : configurer.getWriters()) {
+				if (writer instanceof EncoderHttpMessageWriter) {
+					process(((EncoderHttpMessageWriter<?>) writer).getEncoder());
+				}
+			}
+		}
+
+		private void process(Encoder<?> encoder) {
+			if (encoder instanceof Jackson2JsonEncoder) {
+				Jackson2JsonEncoder jackson2JsonEncoder = (Jackson2JsonEncoder) encoder;
+				jackson2JsonEncoder.registerObjectMappersForType(OperationResponseBody.class, (associations) -> {
+					ObjectMapper objectMapper = this.endpointObjectMapper.get();
+					MEDIA_TYPES.forEach((mimeType) -> associations.put(mimeType, objectMapper));
+				});
+			}
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/endpoint/web/servlet/WebMvcEndpointManagementContextConfiguration.java

@@ -17,9 +17,14 @@
 package org.springframework.boot.actuate.autoconfigure.endpoint.web.servlet;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.boot.actuate.autoconfigure.endpoint.condition.ConditionalOnAvailableEndpoint;
 import org.springframework.boot.actuate.autoconfigure.endpoint.expose.EndpointExposure;
 import org.springframework.boot.actuate.autoconfigure.endpoint.web.CorsEndpointProperties;
@@ -28,7 +33,9 @@ import org.springframework.boot.actuate.autoconfigure.web.ManagementContextConfi
 import org.springframework.boot.actuate.autoconfigure.web.server.ConditionalOnManagementPort;
 import org.springframework.boot.actuate.autoconfigure.web.server.ManagementPortType;
 import org.springframework.boot.actuate.endpoint.ExposableEndpoint;
+import org.springframework.boot.actuate.endpoint.OperationResponseBody;
 import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
+import org.springframework.boot.actuate.endpoint.jackson.EndpointObjectMapper;
 import org.springframework.boot.actuate.endpoint.web.EndpointLinksResolver;
 import org.springframework.boot.actuate.endpoint.web.EndpointMapping;
 import org.springframework.boot.actuate.endpoint.web.EndpointMediaTypes;
@@ -49,9 +56,14 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplicat
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Role;
 import org.springframework.core.env.Environment;
+import org.springframework.http.MediaType;
+import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
 import org.springframework.util.StringUtils;
 import org.springframework.web.servlet.DispatcherServlet;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 
 /**
  * {@link ManagementContextConfiguration @ManagementContextConfiguration} for Spring MVC
@@ -116,4 +128,46 @@ public class WebMvcEndpointManagementContextConfiguration {
 				corsProperties.toCorsConfiguration());
 	}
 
+	@Bean
+	@ConditionalOnBean(EndpointObjectMapper.class)
+	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
+	static EndpointObjectMapperWebMvcConfigurer endpointObjectMapperWebMvcConfigurer(
+			EndpointObjectMapper endpointObjectMapper) {
+		return new EndpointObjectMapperWebMvcConfigurer(endpointObjectMapper);
+	}
+
+	/**
+	 * {@link WebMvcConfigurer} to apply {@link EndpointObjectMapper} for
+	 * {@link OperationResponseBody} to {@link MappingJackson2HttpMessageConverter}
+	 * instances.
+	 */
+	static class EndpointObjectMapperWebMvcConfigurer implements WebMvcConfigurer {
+
+		private static final List<MediaType> MEDIA_TYPES = Collections
+				.unmodifiableList(Arrays.asList(MediaType.APPLICATION_JSON, new MediaType("application", "*+json")));
+
+		private final EndpointObjectMapper endpointObjectMapper;
+
+		EndpointObjectMapperWebMvcConfigurer(EndpointObjectMapper endpointObjectMapper) {
+			this.endpointObjectMapper = endpointObjectMapper;
+		}
+
+		@Override
+		public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
+			for (HttpMessageConverter<?> converter : converters) {
+				if (converter instanceof MappingJackson2HttpMessageConverter) {
+					configure((MappingJackson2HttpMessageConverter) converter);
+				}
+			}
+		}
+
+		private void configure(MappingJackson2HttpMessageConverter converter) {
+			converter.registerObjectMappersForType(OperationResponseBody.class, (associations) -> {
+				ObjectMapper objectMapper = this.endpointObjectMapper.get();
+				MEDIA_TYPES.forEach((mimeType) -> associations.put(mimeType, objectMapper));
+			});
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -60,6 +60,12 @@
       "type": "java.lang.Boolean",
       "description": "Whether to enable or disable all endpoints by default."
     },
+    {
+      "name": "management.endpoints.jackson.isolated-object-mapper",
+      "type": "java.lang.Boolean",
+      "description": "Whether to use an isolated object mapper to serialize endpoint JSON.",
+      "defaultValue": true
+    },
     {
       "name": "management.endpoints.jmx.domain",
       "defaultValue": "org.springframework.boot"

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

@@ -17,6 +17,7 @@ org.springframework.boot.actuate.autoconfigure.couchbase.CouchbaseReactiveHealth
 org.springframework.boot.actuate.autoconfigure.data.elasticsearch.ElasticsearchReactiveHealthContributorAutoConfiguration
 org.springframework.boot.actuate.autoconfigure.elasticsearch.ElasticsearchRestHealthContributorAutoConfiguration
 org.springframework.boot.actuate.autoconfigure.endpoint.EndpointAutoConfiguration
+org.springframework.boot.actuate.autoconfigure.endpoint.jackson.JacksonEndpointAutoConfiguration
 org.springframework.boot.actuate.autoconfigure.endpoint.jmx.JmxEndpointAutoConfiguration
 org.springframework.boot.actuate.autoconfigure.endpoint.web.WebEndpointAutoConfiguration
 org.springframework.boot.actuate.autoconfigure.env.EnvironmentEndpointAutoConfiguration

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

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.endpoint.jackson;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.actuate.endpoint.jackson.EndpointObjectMapper;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link JacksonEndpointAutoConfiguration}.
+ *
+ * @author Phillip Webb
+ */
+class JacksonEndpointAutoConfigurationTests {
+
+	private ApplicationContextRunner runner = new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(JacksonEndpointAutoConfiguration.class));
+
+	@Test
+	void endpointObjectMapperWhenNoProperty() {
+		this.runner.run((context) -> assertThat(context).hasSingleBean(EndpointObjectMapper.class));
+	}
+
+	@Test
+	void endpointObjectMapperWhenPropertyTrue() {
+		this.runner.withPropertyValues("management.endpoints.jackson.isolated-object-mapper=true")
+				.run((context) -> assertThat(context).hasSingleBean(EndpointObjectMapper.class));
+	}
+
+	@Test
+	void endpointObjectMapperWhenPropertyFalse() {
+		this.runner.withPropertyValues("management.endpoints.jackson.isolated-object-mapper=false")
+				.run((context) -> assertThat(context).doesNotHaveBean(EndpointObjectMapper.class));
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class TestEndpointMapperConfiguration {
+
+		@Bean
+		TestEndpointObjectMapper testEndpointObjectMapper() {
+			return new TestEndpointObjectMapper();
+		}
+
+	}
+
+	static class TestEndpointObjectMapper implements EndpointObjectMapper {
+
+		@Override
+		public ObjectMapper get() {
+			return null;
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/integrationtest/EndpointObjectMapperConfiguration.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.integrationtest;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import com.fasterxml.jackson.databind.ser.std.StdScalarSerializer;
+
+import org.springframework.boot.actuate.endpoint.jackson.EndpointObjectMapper;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
+
+/**
+ * {@link Configuration @Configuration} that creates an {@link EndpointObjectMapper} that
+ * reverses all strings.
+ *
+ * @author Phillip Webb
+ */
+@Configuration
+class EndpointObjectMapperConfiguration {
+
+	@Bean
+	EndpointObjectMapper endpointObjectMapper() {
+		SimpleModule module = new SimpleModule();
+		module.addSerializer(String.class, new ReverseStringSerializer());
+		ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json().modules(module).build();
+		return () -> objectMapper;
+	}
+
+	static class ReverseStringSerializer extends StdScalarSerializer<Object> {
+
+		ReverseStringSerializer() {
+			super(String.class, false);
+		}
+
+		@Override
+		public boolean isEmpty(SerializerProvider prov, Object value) {
+			return ((String) value).isEmpty();
+		}
+
+		@Override
+		public void serialize(Object value, JsonGenerator gen, SerializerProvider provider) throws IOException {
+			serialize(value, gen);
+		}
+
+		@Override
+		public final void serializeWithType(Object value, JsonGenerator gen, SerializerProvider provider,
+				TypeSerializer typeSer) throws IOException {
+			serialize(value, gen);
+		}
+
+		private void serialize(Object value, JsonGenerator gen) throws IOException {
+			StringBuilder builder = new StringBuilder((String) value);
+			gen.writeString(builder.reverse().toString());
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/integrationtest/JerseyEndpointIntegrationTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.actuate.autoconfigure.integrationtest;
 
+import java.nio.charset.StandardCharsets;
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -44,6 +45,8 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.test.web.reactive.server.WebTestClient;
 import org.springframework.web.servlet.DispatcherServlet;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 /**
  * Integration tests for the Jersey actuator endpoints.
  *
@@ -87,7 +90,22 @@ class JerseyEndpointIntegrationTests {
 					.responseTimeout(Duration.ofMinutes(5)).build();
 			client.get().uri("/actuator").exchange().expectStatus().isUnauthorized();
 		});
+	}
 
+	@Test
+	void endpointObjectMapperCanBeApplied() {
+		WebApplicationContextRunner contextRunner = getContextRunner(new Class<?>[] { EndpointsConfiguration.class,
+				ResourceConfigConfiguration.class, EndpointObjectMapperConfiguration.class });
+		contextRunner.run((context) -> {
+			int port = context.getSourceApplicationContext(AnnotationConfigServletWebServerApplicationContext.class)
+					.getWebServer().getPort();
+			WebTestClient client = WebTestClient.bindToServer().baseUrl("http://localhost:" + port)
+					.responseTimeout(Duration.ofMinutes(5)).build();
+			client.get().uri("/actuator/beans").exchange().expectStatus().isOk().expectBody().consumeWith((result) -> {
+				String json = new String(result.getResponseBody(), StandardCharsets.UTF_8);
+				assertThat(json).contains("\"scope\":\"notelgnis\"");
+			});
+		});
 	}
 
 	protected void testJerseyEndpoints(Class<?>[] userConfigurations) {

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/integrationtest/WebFluxEndpointIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 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 +16,8 @@
 
 package org.springframework.boot.actuate.autoconfigure.integrationtest;
 
+import java.nio.charset.StandardCharsets;
+
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.actuate.autoconfigure.beans.BeansEndpointAutoConfiguration;
@@ -36,6 +38,8 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.test.web.reactive.server.WebTestClient;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 /**
  * Integration tests for the WebFlux actuator endpoints.
  *
@@ -68,6 +72,19 @@ class WebFluxEndpointIntegrationTests {
 		});
 	}
 
+	@Test
+	void endpointObjectMapperCanBeApplied() {
+		this.contextRunner.withUserConfiguration(EndpointObjectMapperConfiguration.class)
+				.withPropertyValues("management.endpoints.web.exposure.include:*").run((context) -> {
+					WebTestClient client = createWebTestClient(context);
+					client.get().uri("/actuator/beans").exchange().expectStatus().isOk().expectBody()
+							.consumeWith((result) -> {
+								String json = new String(result.getResponseBody(), StandardCharsets.UTF_8);
+								assertThat(json).contains("\"scope\":\"notelgnis\"");
+							});
+				});
+	}
+
 	private WebTestClient createWebTestClient(ApplicationContext context) {
 		return WebTestClient.bindToApplicationContext(context).configureClient().baseUrl("https://spring.example.org")
 				.build();

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/integrationtest/WebMvcEndpointIntegrationTests.java

@@ -52,6 +52,7 @@ import org.springframework.mock.web.MockServletContext;
 import org.springframework.security.authentication.TestingAuthenticationToken;
 import org.springframework.security.test.context.TestSecurityContextHolder;
 import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.MvcResult;
 import org.springframework.test.web.servlet.setup.DefaultMockMvcBuilder;
 import org.springframework.test.web.servlet.setup.MockMvcBuilders;
 import org.springframework.test.web.servlet.setup.MockMvcConfigurer;
@@ -140,6 +141,16 @@ class WebMvcEndpointIntegrationTests {
 		mockMvc.perform(get("/actuator").accept("*/*")).andExpect(status().isNotFound());
 	}
 
+	@Test
+	void endpointObjectMapperCanBeApplied() throws Exception {
+		this.context = new AnnotationConfigServletWebApplicationContext();
+		this.context.register(EndpointObjectMapperConfiguration.class, DefaultConfiguration.class);
+		TestPropertyValues.of("management.endpoints.web.exposure.include=*").applyTo(this.context);
+		MockMvc mockMvc = doCreateMockMvc();
+		MvcResult result = mockMvc.perform(get("/actuator/beans")).andExpect(status().isOk()).andReturn();
+		assertThat(result.getResponse().getContentAsString()).contains("\"scope\":\"notelgnis\"");
+	}
+
 	private MockMvc createSecureMockMvc() {
 		return doCreateMockMvc(springSecurity());
 	}

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/Operation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -32,7 +32,9 @@ public interface Operation {
 	OperationType getType();
 
 	/**
-	 * Invoke the underlying operation using the given {@code context}.
+	 * Invoke the underlying operation using the given {@code context}. Results intended
+	 * to be returned in the body of the response should additionally implement
+	 * {@link OperationResponseBody}.
 	 * @param context the context in to use when invoking the operation
 	 * @return the result of the operation, may be {@code null}
 	 */

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/OperationResponseBody.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.endpoint;
+
+import java.util.Map;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+/**
+ * Tagging interface used to indicate that an operation result is intended to be returned
+ * in the body of the response. Primarily intended to support JSON serialzation using an
+ * endpoint specific {@link ObjectMapper}.
+ *
+ * @author Phillip Webb
+ * @since 3.0.0
+ */
+public interface OperationResponseBody {
+
+	/**
+	 * Return a {@link OperationResponseBody} {@link Map} instance containing entires from
+	 * the given {@code map}.
+	 * @param <K> the key type
+	 * @param <V> the value type
+	 * @param map the source map or {@code null}
+	 * @return a {@link OperationResponseBody} version of the map or {@code null}
+	 */
+	static <K, V> Map<K, V> of(Map<K, V> map) {
+		return (map != null) ? new OperationResponseBodyMap<>(map) : null;
+	}
+
+}

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/OperationResponseBodyMap.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.endpoint;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * {@link LinkedHashMap} to support {@link OperationResponseBody#of(java.util.Map)}.
+ *
+ * @param <K> the key type
+ * @param <V> the value type
+ * @author Phillip Webb
+ */
+class OperationResponseBodyMap<K, V> extends LinkedHashMap<K, V> implements OperationResponseBody {
+
+	OperationResponseBodyMap(Map<? extends K, ? extends V> map) {
+		super(map);
+	}
+
+}

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

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.endpoint.jackson;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import org.springframework.boot.actuate.endpoint.OperationResponseBody;
+
+/**
+ * Interface used to supply the {@link ObjectMapper} that should be used when serializing
+ * {@link OperationResponseBody} endpoint results.
+ *
+ * @author Phillip Webb
+ * @since 3.0.0
+ * @see OperationResponseBody
+ */
+public interface EndpointObjectMapper {
+
+	/**
+	 * Return the {@link ObjectMapper} that should be used to serialize
+	 * {@link OperationResponseBody} endpoint results.
+	 * @return the object mapper
+	 */
+	ObjectMapper get();
+
+}

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/jackson/package-info.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Jackson support classes for actuator endpoints.
+ */
+package org.springframework.boot.actuate.endpoint.jackson;

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/OperationResponseBodyTests.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2012-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.endpoint;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.entry;
+
+/**
+ * Tests for {@link OperationResponseBody}.
+ *
+ * @author Phillip Webb
+ */
+class OperationResponseBodyTests {
+
+	@Test
+	void ofMapReturnsOperationResponseBody() {
+		LinkedHashMap<String, String> map = new LinkedHashMap<>();
+		map.put("one", "1");
+		map.put("two", "2");
+		Map<String, String> mapDescriptor = OperationResponseBody.of(map);
+		assertThat(mapDescriptor).containsExactly(entry("one", "1"), entry("two", "2"));
+		assertThat(mapDescriptor).isInstanceOf(OperationResponseBody.class);
+	}
+
+}