Apply spring.jackson.* config to HypermediaAutoConfiguration’s ObjectMapper

Previously, HypermediaAutoConfiguration would trigger the creation of
an ObjectMapper bean named _halObjectMapper. This bean did not have the
spring.jackson.* configuration applied to it, however its presence
would revent JacksonAutoConfiguration from creating its
ObjectMapper. This left the user with an ObjectMapper that did not
honour the spring.jackson.* configuration.

This commit updates HypermediaAutoConfiguration to use the
Jackson2ObjectMapperBuilder that may have been created by
JacksonAutoConfiguration. If the builder exists it is used to configure
the _halObjectMapper bean.

Fixes gh-1949

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/hateoas/HypermediaAutoConfiguration.java

@@ -16,12 +16,17 @@
 
 package org.springframework.boot.autoconfigure.hateoas;
 
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.config.BeanPostProcessor;
 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.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
+import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.hateoas.EntityLinks;
 import org.springframework.hateoas.LinkDiscoverers;
@@ -29,27 +34,63 @@ import org.springframework.hateoas.Resource;
 import org.springframework.hateoas.config.EnableEntityLinks;
 import org.springframework.hateoas.config.EnableHypermediaSupport;
 import org.springframework.hateoas.config.EnableHypermediaSupport.HypermediaType;
+import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
 import org.springframework.plugin.core.Plugin;
 import org.springframework.web.bind.annotation.RequestMapping;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for Spring HATEOAS's
  * {@link EnableHypermediaSupport}.
  *
  * @author Roy Clarkson
  * @author Oliver Gierke
+ * @author Andy Wilkinson
  * @since 1.1.0
  */
 @Configuration
 @ConditionalOnClass({ Resource.class, RequestMapping.class, Plugin.class })
 @ConditionalOnWebApplication
-@AutoConfigureAfter(WebMvcAutoConfiguration.class)
+@AutoConfigureAfter({ WebMvcAutoConfiguration.class, JacksonAutoConfiguration.class })
 public class HypermediaAutoConfiguration {
 
 	@Configuration
 	@ConditionalOnMissingBean(LinkDiscoverers.class)
 	@EnableHypermediaSupport(type = HypermediaType.HAL)
 	protected static class HypermediaConfiguration {
+
+		@ConditionalOnClass({ Jackson2ObjectMapperBuilder.class, ObjectMapper.class })
+		protected static class HalObjectMapperConfiguration {
+
+			@Autowired(required = false)
+			private Jackson2ObjectMapperBuilder objectMapperBuilder;
+
+			@Bean
+			public BeanPostProcessor halObjectMapperConfigurer() {
+				return new BeanPostProcessor() {
+
+					@Override
+					public Object postProcessAfterInitialization(Object bean,
+							String beanName) throws BeansException {
+						if (HalObjectMapperConfiguration.this.objectMapperBuilder != null
+								&& bean instanceof ObjectMapper
+								&& "_halObjectMapper".equals(beanName)) {
+							HalObjectMapperConfiguration.this.objectMapperBuilder
+									.configure((ObjectMapper) bean);
+						}
+						return bean;
+					}
+
+					@Override
+					public Object postProcessBeforeInitialization(Object bean,
+							String beanName) throws BeansException {
+						return bean;
+					}
+
+				};
+			}
+		}
 	}
 
 	@Configuration

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/hateoas/HypermediaAutoConfigurationTests.java

@@ -18,6 +18,8 @@ package org.springframework.boot.autoconfigure.hateoas;
 
 import org.junit.After;
 import org.junit.Test;
+import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
+import org.springframework.boot.test.EnvironmentTestUtils;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.hateoas.EntityLinks;
 import org.springframework.hateoas.LinkDiscoverer;
@@ -28,6 +30,9 @@ import org.springframework.hateoas.config.EnableHypermediaSupport.HypermediaType
 import org.springframework.hateoas.hal.HalLinkDiscoverer;
 import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 
@@ -78,6 +83,20 @@ public class HypermediaAutoConfigurationTests {
 		this.context.getBean(LinkDiscoverers.class);
 	}
 
+	@Test
+	public void jacksonConfigurationIsAppliedToTheHalObjectMapper() {
+		this.context = new AnnotationConfigWebApplicationContext();
+		this.context.register(HypermediaAutoConfiguration.class,
+				JacksonAutoConfiguration.class);
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"spring.jackson.serialization.INDENT_OUTPUT:true");
+		this.context.refresh();
+		ObjectMapper objectMapper = this.context.getBean("_halObjectMapper",
+				ObjectMapper.class);
+		assertTrue(objectMapper.getSerializationConfig().isEnabled(
+				SerializationFeature.INDENT_OUTPUT));
+	}
+
 	@Configuration
 	@EnableHypermediaSupport(type = HypermediaType.HAL)
 	static class SampleConfig {