Support JMX endpoints when only Jackson 2 is present

Closes gh-47688

module/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/endpoint/jmx/JmxEndpointAutoConfiguration.java

@@ -18,6 +18,7 @@ package org.springframework.boot.actuate.autoconfigure.endpoint.jmx;
 
 import javax.management.MBeanServer;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
 import tools.jackson.databind.json.JsonMapper;
 
 import org.springframework.beans.factory.ObjectProvider;
@@ -44,6 +45,7 @@ import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBooleanProperty;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnSingleCandidate;
 import org.springframework.boot.autoconfigure.condition.SearchStrategy;
 import org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration;
@@ -133,4 +135,24 @@ public final class JmxEndpointAutoConfiguration {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnClass(ObjectMapper.class)
+	@ConditionalOnMissingClass("tools.jackson.databind.json.JsonMapper")
+	@Deprecated(since = "4.2.0", forRemoval = true)
+	@SuppressWarnings("removal")
+	static class JmxJackson2EndpointConfiguration {
+
+		@Bean
+		@ConditionalOnSingleCandidate(MBeanServer.class)
+		JmxEndpointExporter jmxMBeanExporter(MBeanServer mBeanServer,
+				EndpointObjectNameFactory endpointObjectNameFactory, ObjectProvider<ObjectMapper> objectMapper,
+				JmxEndpointsSupplier jmxEndpointsSupplier) {
+			JmxOperationResponseMapper responseMapper = new org.springframework.boot.actuate.endpoint.jmx.Jackson2JmxOperationResponseMapper(
+					objectMapper.getIfAvailable());
+			return new JmxEndpointExporter(mBeanServer, endpointObjectNameFactory, responseMapper,
+					jmxEndpointsSupplier.getEndpoints());
+		}
+
+	}
+
 }

module/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/jmx/Jackson2JmxOperationResponseMapper.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2012-present 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.jmx;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+
+import com.fasterxml.jackson.databind.JavaType;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.jspecify.annotations.Nullable;
+
+import org.springframework.lang.Contract;
+
+/**
+ * {@link JmxOperationResponseMapper} that delegates to a Jackson 2 {@link ObjectMapper}
+ * to return a JSON response.
+ *
+ * @author Stephane Nicoll
+ * @since 4.0.0
+ * @deprecated since 4.0.0 for removal in 4.2.0 in favor of
+ * {@link JacksonJmxOperationResponseMapper}.
+ */
+@Deprecated(since = "4.0.0", forRemoval = true)
+public class Jackson2JmxOperationResponseMapper implements JmxOperationResponseMapper {
+
+	private final ObjectMapper objectMapper;
+
+	private final JavaType listType;
+
+	private final JavaType mapType;
+
+	public Jackson2JmxOperationResponseMapper(@Nullable ObjectMapper objectMapper) {
+		this.objectMapper = (objectMapper != null) ? objectMapper : new ObjectMapper();
+		this.listType = this.objectMapper.getTypeFactory().constructParametricType(List.class, Object.class);
+		this.mapType = this.objectMapper.getTypeFactory()
+			.constructParametricType(Map.class, String.class, Object.class);
+	}
+
+	@Override
+	public Class<?> mapResponseType(Class<?> responseType) {
+		if (CharSequence.class.isAssignableFrom(responseType)) {
+			return String.class;
+		}
+		if (responseType.isArray() || Collection.class.isAssignableFrom(responseType)) {
+			return List.class;
+		}
+		return Map.class;
+	}
+
+	@Override
+	@Contract("!null -> !null")
+	public @Nullable Object mapResponse(@Nullable Object response) {
+		if (response == null) {
+			return null;
+		}
+		if (response instanceof CharSequence) {
+			return response.toString();
+		}
+		if (response.getClass().isArray() || response instanceof Collection) {
+			return this.objectMapper.convertValue(response, this.listType);
+		}
+		return this.objectMapper.convertValue(response, this.mapType);
+	}
+
+}

smoke-test/spring-boot-smoke-test-jackson2-only/src/main/resources/application.properties

@@ -1 +1,3 @@
+management.endpoints.jmx.exposure.include=*
 management.endpoints.web.exposure.include=*
+

smoke-test/spring-boot-smoke-test-jackson2-only/src/test/java/smoketest/jackson2/only/SampleJackson2OnlyApplicationTests.java

@@ -16,8 +16,12 @@
 
 package smoketest.jackson2.only;
 
+import java.lang.management.ManagementFactory;
 import java.util.Map;
 
+import javax.management.MBeanServer;
+import javax.management.ObjectName;
+
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.annotation.Autowired;
@@ -33,7 +37,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  *
  * @author Andy Wilkinson
  */
-@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT, properties = "spring.jmx.enabled=true")
 @AutoConfigureRestTestClient
 class SampleJackson2OnlyApplicationTests {
 
@@ -64,4 +68,14 @@ class SampleJackson2OnlyApplicationTests {
 			.value((body) -> assertThat(body).containsOnlyKeys("_links"));
 	}
 
+	@Test
+	@SuppressWarnings("unchecked")
+	void jmxEndpointsShouldWork() throws Exception {
+		MBeanServer mbeanServer = ManagementFactory.getPlatformMBeanServer();
+		Map<String, Object> result = (Map<String, Object>) mbeanServer.invoke(
+				ObjectName.getInstance("org.springframework.boot:type=Endpoint,name=Configprops"),
+				"configurationProperties", new Object[0], null);
+		assertThat(result).containsOnlyKeys("contexts");
+	}
+
 }