Separate the configuration/creation of the default ObjectMapper

bean from the registration of Jackson modules to avoid circular creation
of the default ObjectMapper bean (and thus failing to obtain the ObjectMapper
and registering the module(s)).

Fixes gh-1132

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jackson/JacksonAutoConfiguration.java

@@ -55,26 +55,11 @@ import com.fasterxml.jackson.datatype.jsr310.JSR310Module;
  */
 @Configuration
 @ConditionalOnClass(ObjectMapper.class)
-@EnableConfigurationProperties(HttpMapperProperties.class)
 public class JacksonAutoConfiguration {
 
-	@Autowired
-	private HttpMapperProperties properties = new HttpMapperProperties();
-
 	@Autowired
 	private ListableBeanFactory beanFactory;
 
-	@Bean
-	@Primary
-	@ConditionalOnMissingBean
-	public ObjectMapper jacksonObjectMapper() {
-		ObjectMapper objectMapper = new ObjectMapper();
-		if (this.properties.isJsonSortKeys()) {
-			objectMapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);
-		}
-		return objectMapper;
-	}
-
 	@PostConstruct
 	private void registerModulesWithObjectMappers() {
 		Collection<Module> modules = getBeans(Module.class);
@@ -88,6 +73,27 @@ public class JacksonAutoConfiguration {
 				.values();
 	}
 
+    @Configuration
+    @ConditionalOnClass(ObjectMapper.class)
+    @EnableConfigurationProperties(HttpMapperProperties.class)
+    static class JacksonObjectMapperAutoConfiguration {
+
+        @Autowired
+       	private HttpMapperProperties properties = new HttpMapperProperties();
+
+        @Bean
+       	@Primary
+       	@ConditionalOnMissingBean
+       	public ObjectMapper jacksonObjectMapper() {
+       		ObjectMapper objectMapper = new ObjectMapper();
+       		if (this.properties.isJsonSortKeys()) {
+       			objectMapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);
+       		}
+       		return objectMapper;
+       	}
+
+    }
+
 	@Configuration
 	@ConditionalOnClass(JodaModule.class)
 	static class JodaModuleAutoConfiguration {