Fix Actuator with Jackson 2 but no spring-web

Previously, if Actuator was being used in a non-web app such that
spring-web was not on the classpath, the app would fail to start
if Jackson 2 was present. This occured as the auto-configuration
for the EndpointJackson2ObjectMapper tried to use spring-web's
Jackson2ObjectMapperBuilder that was not present.

This commit updates the auto-configuration to back off when
Jackson2ObjectMapperBuilder is absent, aligning it with the
behavior of JacksonEndpointAutoConfiguration in 3.5.

Fixes gh-47788

Author: wilkinsona

module/spring-boot-actuator-autoconfigure/build.gradle

@@ -48,6 +48,7 @@ dependencies {
 	testCompileOnly("com.google.code.findbugs:jsr305")
 
 	testRuntimeOnly("ch.qos.logback:logback-classic")
+	testRuntimeOnly("com.fasterxml.jackson.datatype:jackson-datatype-jsr310")
 }
 
 tasks.named("compileTestJava") {

module/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/endpoint/jackson/Jackson2EndpointAutoConfiguration.java

@@ -20,13 +20,11 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationFeature;
 
-import org.springframework.boot.actuate.endpoint.jackson.EndpointJackson2ObjectMapper;
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBooleanProperty;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.context.annotation.Bean;
-import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for Endpoint Jackson 2 support.
@@ -36,15 +34,15 @@
  * @deprecated since 4.0.0 for removal in 4.2.0 in favor of Jackson 3.
  */
 @AutoConfiguration
-@ConditionalOnClass(ObjectMapper.class)
+@ConditionalOnClass({ ObjectMapper.class, org.springframework.http.converter.json.Jackson2ObjectMapperBuilder.class })
 @Deprecated(since = "4.0.0", forRemoval = true)
 @SuppressWarnings("removal")
 public final class Jackson2EndpointAutoConfiguration {
 
 	@Bean
 	@ConditionalOnBooleanProperty(name = "management.endpoints.jackson.isolated-object-mapper", matchIfMissing = true)
-	EndpointJackson2ObjectMapper jackson2EndpointJsonMapper() {
-		ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json()
+	org.springframework.boot.actuate.endpoint.jackson.EndpointJackson2ObjectMapper jackson2EndpointJsonMapper() {
+		ObjectMapper objectMapper = org.springframework.http.converter.json.Jackson2ObjectMapperBuilder.json()
 			.featuresToDisable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS,
 					SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS)
 			.serializationInclusion(Include.NON_NULL)

module/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/endpoint/jackson/Jackson2EndpointAutoConfigurationTests.java

@@ -0,0 +1,135 @@
+/*
+ * 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.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;
+import tools.jackson.databind.json.JsonMapper;
+
+import org.springframework.boot.actuate.endpoint.jackson.EndpointJsonMapper;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.FilteredClassLoader;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link Jackson2EndpointAutoConfiguration}.
+ *
+ * @author Phillip Webb
+ * @author Andy Wilkinson
+ * @deprecated since 4.0.0 for removal in 4.2.0 in favor of Jackson 3
+ */
+@SuppressWarnings("removal")
+@Deprecated(since = "4.0.0", forRemoval = true)
+class Jackson2EndpointAutoConfigurationTests {
+
+	private final ApplicationContextRunner runner = new ApplicationContextRunner()
+		.withConfiguration(AutoConfigurations.of(Jackson2EndpointAutoConfiguration.class));
+
+	@Test
+	void endpointObjectMapperWhenNoProperty() {
+		this.runner.run((context) -> assertThat(context)
+			.hasSingleBean(org.springframework.boot.actuate.endpoint.jackson.EndpointJackson2ObjectMapper.class));
+	}
+
+	@Test
+	void endpointObjectMapperWhenPropertyTrue() {
+		this.runner.run((context) -> assertThat(context)
+			.hasSingleBean(org.springframework.boot.actuate.endpoint.jackson.EndpointJackson2ObjectMapper.class));
+	}
+
+	@Test
+	void endpointObjectMapperWhenPropertyFalse() {
+		this.runner.withPropertyValues("management.endpoints.jackson.isolated-object-mapper=false")
+			.run((context) -> assertThat(context)
+				.doesNotHaveBean(org.springframework.boot.actuate.endpoint.jackson.EndpointJackson2ObjectMapper.class));
+	}
+
+	@Test
+	void endpointObjectMapperWhenSpringWebIsAbsent() {
+		this.runner.withClassLoader(new FilteredClassLoader(Jackson2ObjectMapperBuilder.class))
+			.run((context) -> assertThat(context)
+				.doesNotHaveBean(org.springframework.boot.actuate.endpoint.jackson.EndpointJackson2ObjectMapper.class));
+	}
+
+	@Test
+	void endpointObjectMapperDoesNotSerializeDatesAsTimestamps() {
+		this.runner.run((context) -> {
+			ObjectMapper objectMapper = context
+				.getBean(org.springframework.boot.actuate.endpoint.jackson.EndpointJackson2ObjectMapper.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(org.springframework.boot.actuate.endpoint.jackson.EndpointJackson2ObjectMapper.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(org.springframework.boot.actuate.endpoint.jackson.EndpointJackson2ObjectMapper.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 {
+
+		@Bean
+		TestEndpointJsonMapper testEndpointJsonMapper() {
+			return new TestEndpointJsonMapper();
+		}
+
+	}
+
+	static class TestEndpointJsonMapper implements EndpointJsonMapper {
+
+		@Override
+		public JsonMapper get() {
+			return new JsonMapper();
+		}
+
+	}
+
+}

smoke-test/spring-boot-smoke-test-jackson2-only/build.gradle

@@ -31,4 +31,5 @@ dependencies {
 	testImplementation(project(":starter:spring-boot-starter-webmvc-test")) {
 		exclude module: 'spring-boot-starter-jackson'
 	}
+	testImplementation(project(":test-support:spring-boot-test-support"))
 }

smoke-test/spring-boot-smoke-test-jackson2-only/src/test/java/smoketest/jackson2/only/SampleJackson2OnlyWithoutSpringWebApplicationTests.java

@@ -0,0 +1,52 @@
+/*
+ * 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 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.boot.test.context.SpringBootTest;
+import org.springframework.boot.testsupport.classpath.ClassPathExclusions;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for Actuator running in {@link SampleJackson2OnlyApplication} with
+ * {@code spring-web} on the classpath.
+ *
+ * @author Andy Wilkinson
+ */
+@ClassPathExclusions("spring-web-*")
+@SpringBootTest(properties = "spring.jmx.enabled=true")
+class SampleJackson2OnlyWithoutSpringWebApplicationTests {
+
+	@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");
+	}
+
+}