Allow Jackson's serialization inclusion to be configured via the env

This commit adds support for configuring an ObjectMapper's
serialization inclusion using the environment via the
spring.jackson.serialization-inclusion property. The property's value
should be one of the values on the JsonInclude.Include enumeration.
Relaxed binding of the property value to the enum is supported. For
example:

spring.jackson.serialization-inclusion: non_null

Closes gh-2532

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

@@ -176,6 +176,10 @@ public Jackson2ObjectMapperBuilder jacksonObjectMapperBuilder() {
 			if (isJsonPrettyPrint != null && isJsonPrettyPrint) {
 				builder.featuresToEnable(SerializationFeature.INDENT_OUTPUT);
 			}
+			if (this.jacksonProperties.getSerializationInclusion() != null) {
+				builder.serializationInclusion(this.jacksonProperties
+						.getSerializationInclusion());
+			}
 			configureFeatures(builder, this.jacksonProperties.getDeserialization());
 			configureFeatures(builder, this.jacksonProperties.getSerialization());
 			configureFeatures(builder, this.jacksonProperties.getMapper());

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

@@ -21,6 +21,7 @@
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
 
+import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.databind.DeserializationFeature;
@@ -45,8 +46,7 @@ public class JacksonProperties {
 
 	/**
 	 * Joda date time format string (yyyy-MM-dd HH:mm:ss). If not configured,
-	 * "date-format" will be used as a fallback if it is configured with a format
-	 * string.
+	 * "date-format" will be used as a fallback if it is configured with a format string.
 	 */
 	private String jodaDateTimeFormat;
 
@@ -82,6 +82,12 @@ public class JacksonProperties {
 	 */
 	private Map<JsonGenerator.Feature, Boolean> generator = new HashMap<JsonGenerator.Feature, Boolean>();
 
+	/**
+	 * Controls the inclusion of properties during serialization. Configured with one of
+	 * the values in Jackson's JsonInclude.Include enumeration.
+	 */
+	private JsonInclude.Include serializationInclusion;
+
 	public String getDateFormat() {
 		return this.dateFormat;
 	}
@@ -126,4 +132,12 @@ public Map<JsonGenerator.Feature, Boolean> getGenerator() {
 		return this.generator;
 	}
 
+	public JsonInclude.Include getSerializationInclusion() {
+		return this.serializationInclusion;
+	}
+
+	public void setSerializationInclusion(JsonInclude.Include serializationInclusion) {
+		this.serializationInclusion = serializationInclusion;
+	}
+
 }

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jackson/JacksonAutoConfigurationTests.java

@@ -37,6 +37,7 @@
 import org.springframework.context.annotation.Primary;
 import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
 
+import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.core.JsonProcessingException;
@@ -387,6 +388,28 @@ public void moduleBeansAndWellKnownModulesAreRegisteredWithTheObjectMapperBuilde
 		assertThat(objectMapper.canSerialize(LocalDateTime.class), is(true));
 	}
 
+	@Test
+	public void defaultSerializationInclusion() {
+		this.context.register(JacksonAutoConfiguration.class);
+		this.context.refresh();
+		ObjectMapper objectMapper = this.context.getBean(
+				Jackson2ObjectMapperBuilder.class).build();
+		assertThat(objectMapper.getSerializationConfig().getSerializationInclusion(),
+				is(JsonInclude.Include.ALWAYS));
+	}
+
+	@Test
+	public void customSerializationInclusion() {
+		this.context.register(JacksonAutoConfiguration.class);
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"spring.jackson.serialization-inclusion:non_null");
+		this.context.refresh();
+		ObjectMapper objectMapper = this.context.getBean(
+				Jackson2ObjectMapperBuilder.class).build();
+		assertThat(objectMapper.getSerializationConfig().getSerializationInclusion(),
+				is(JsonInclude.Include.NON_NULL));
+	}
+
 	@Configuration
 	protected static class MockObjectMapperConfig {
 

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -142,6 +142,7 @@ content into your application; rather pick only the properties that you need.
 	spring.jackson.mapper.*= # see Jackson's MapperFeature
 	spring.jackson.parser.*= # see Jackson's JsonParser.Feature
 	spring.jackson.serialization.*= # see Jackson's SerializationFeature
+	spring.jackson.serialization-inclusion= # Controls the inclusion of properties during serialization (see Jackson's JsonInclude.Include)
 
 	# THYMELEAF ({sc-spring-boot-autoconfigure}/thymeleaf/ThymeleafAutoConfiguration.{sc-ext}[ThymeleafAutoConfiguration])
 	spring.thymeleaf.check-template-location=true