Make Jackson date format and property naming strategy configurable

Allow the environment to be used to configure Jackson's date format
and property naming strategy

Closes gh-1628

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

@@ -16,11 +16,15 @@
 
 package org.springframework.boot.autoconfigure.jackson;
 
+import java.lang.reflect.Field;
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
 import java.util.Collection;
 import java.util.Map.Entry;
 
 import javax.annotation.PostConstruct;
 
+import org.springframework.beans.BeanUtils;
 import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.beans.factory.ListableBeanFactory;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -33,6 +37,8 @@ import org.springframework.boot.context.properties.EnableConfigurationProperties
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Primary;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
 
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.core.JsonParser;
@@ -40,6 +46,7 @@ import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.MapperFeature;
 import com.fasterxml.jackson.databind.Module;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.PropertyNamingStrategy;
 import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.datatype.joda.JodaModule;
 import com.fasterxml.jackson.datatype.jsr310.JSR310Module;
@@ -57,6 +64,7 @@ import com.fasterxml.jackson.datatype.jsr310.JSR310Module;
  *
  * @author Oliver Gierke
  * @author Andy Wilkinson
+ * @author Marcel Overdijk
  * @since 1.1.0
  */
 @Configuration
@@ -107,9 +115,65 @@ public class JacksonAutoConfiguration {
 			configureParserFeatures(objectMapper);
 			configureGeneratorFeatures(objectMapper);
 
+			configureDateFormat(objectMapper);
+			configurePropertyNamingStrategy(objectMapper);
+
 			return objectMapper;
 		}
 
+		private void configurePropertyNamingStrategy(ObjectMapper objectMapper) {
+			// We support a fully qualified class name extending Jackson's
+			// PropertyNamingStrategy or a string value corresponding to the constant
+			// names in PropertyNamingStrategy which hold default provided implementations
+			String propertyNamingStrategy = this.jacksonProperties
+					.getPropertyNamingStrategy();
+			if (propertyNamingStrategy != null) {
+				try {
+					Class<?> clazz = ClassUtils.forName(propertyNamingStrategy, null);
+					objectMapper
+							.setPropertyNamingStrategy((PropertyNamingStrategy) BeanUtils
+									.instantiateClass(clazz));
+				}
+				catch (ClassNotFoundException e) {
+					// Find the field (this way we automatically support new constants
+					// that may be added by Jackson in the future)
+					Field field = ReflectionUtils.findField(PropertyNamingStrategy.class,
+							propertyNamingStrategy, PropertyNamingStrategy.class);
+					if (field != null) {
+						try {
+							objectMapper
+									.setPropertyNamingStrategy((PropertyNamingStrategy) field
+											.get(null));
+						}
+						catch (Exception ex) {
+							throw new IllegalStateException(ex);
+						}
+					}
+					else {
+						throw new IllegalArgumentException("Constant named '"
+								+ propertyNamingStrategy + "' not found on "
+								+ PropertyNamingStrategy.class.getName());
+					}
+				}
+			}
+		}
+
+		private void configureDateFormat(ObjectMapper objectMapper) {
+			// We support a fully qualified class name extending DateFormat or a date
+			// pattern string value
+			String dateFormat = this.jacksonProperties.getDateFormat();
+			if (dateFormat != null) {
+				try {
+					Class<?> clazz = ClassUtils.forName(dateFormat, null);
+					objectMapper.setDateFormat((DateFormat) BeanUtils
+							.instantiateClass(clazz));
+				}
+				catch (ClassNotFoundException e) {
+					objectMapper.setDateFormat(new SimpleDateFormat(dateFormat));
+				}
+			}
+		}
+
 		private void configureDeserializationFeatures(ObjectMapper objectMapper) {
 			for (Entry<DeserializationFeature, Boolean> entry : this.jacksonProperties
 					.getDeserialization().entrySet()) {

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

@@ -31,11 +31,16 @@ import com.fasterxml.jackson.databind.SerializationFeature;
  * Configuration properties to configure Jackson
  *
  * @author Andy Wilkinson
+ * @author Marcel Overdijk
  * @since 1.2.0
  */
 @ConfigurationProperties(prefix = "spring.jackson")
 public class JacksonProperties {
 
+	private String dateFormat;
+
+	private String propertyNamingStrategy;
+
 	private Map<SerializationFeature, Boolean> serialization = new HashMap<SerializationFeature, Boolean>();
 
 	private Map<DeserializationFeature, Boolean> deserialization = new HashMap<DeserializationFeature, Boolean>();
@@ -46,6 +51,22 @@ public class JacksonProperties {
 
 	private Map<JsonGenerator.Feature, Boolean> generator = new HashMap<JsonGenerator.Feature, Boolean>();
 
+	public String getDateFormat() {
+		return this.dateFormat;
+	}
+
+	public void setDateFormat(String dateFormat) {
+		this.dateFormat = dateFormat;
+	}
+
+	public String getPropertyNamingStrategy() {
+		return this.propertyNamingStrategy;
+	}
+
+	public void setPropertyNamingStrategy(String propertyNamingStrategy) {
+		this.propertyNamingStrategy = propertyNamingStrategy;
+	}
+
 	public Map<SerializationFeature, Boolean> getSerialization() {
 		return this.serialization;
 	}

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

@@ -17,8 +17,11 @@
 package org.springframework.boot.autoconfigure.jackson;
 
 import java.io.IOException;
+import java.text.SimpleDateFormat;
+import java.util.Date;
 import java.util.Map;
 
+import org.joda.time.DateTime;
 import org.joda.time.LocalDateTime;
 import org.junit.After;
 import org.junit.Before;
@@ -60,6 +63,8 @@ import static org.mockito.Mockito.verify;
  *
  * @author Dave Syer
  * @author Oliver Gierke
+ * @author Andy Wilkinson
+ * @author Marcel Overdijk
  */
 public class JacksonAutoConfigurationTests {
 
@@ -108,6 +113,110 @@ public class JacksonAutoConfigurationTests {
 		assertEquals("{\"foo\":\"bar\"}", mapper.writeValueAsString(new Foo()));
 	}
 
+	/*
+	 * ObjectMapper does not contain method to get the date format of the mapper. See
+	 * https://github.com/FasterXML/jackson-databind/issues/559 If such a method will be
+	 * provided below tests can be simplified.
+	 */
+
+	@Test
+	public void noCustomDateFormat() throws Exception {
+		this.context.register(JacksonAutoConfiguration.class);
+		this.context.refresh();
+		ObjectMapper mapper = this.context.getBean(ObjectMapper.class);
+		Date date = new DateTime(1988, 6, 25, 20, 30).toDate();
+		assertEquals(String.valueOf(date.getTime()), mapper.writeValueAsString(date));
+	}
+
+	@Test
+	public void customDateFormat() throws Exception {
+		this.context.register(JacksonAutoConfiguration.class);
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"spring.jackson.date-format:yyyyMMddHHmmss");
+		this.context.refresh();
+		ObjectMapper mapper = this.context.getBean(ObjectMapper.class);
+		Date date = new DateTime(1988, 6, 25, 20, 30).toDate();
+		assertEquals("\"19880625203000\"", mapper.writeValueAsString(date));
+	}
+
+	@Test
+	public void customDateFormatClass() throws Exception {
+		this.context.register(JacksonAutoConfiguration.class);
+		EnvironmentTestUtils
+				.addEnvironment(
+						this.context,
+						"spring.jackson.date-format:org.springframework.boot.autoconfigure.jackson.JacksonAutoConfigurationTests.MyDateFormat");
+		this.context.refresh();
+		ObjectMapper mapper = this.context.getBean(ObjectMapper.class);
+		Date date = new DateTime(1988, 6, 25, 20, 30).toDate();
+		assertEquals("\"1988-06-25 20:30:00\"", mapper.writeValueAsString(date));
+	}
+
+	public static class MyDateFormat extends SimpleDateFormat {
+
+		public MyDateFormat() {
+			super("yyyy-MM-dd HH:mm:ss");
+		}
+	}
+
+	/*
+	 * ObjectMapper does not contain method to get the property naming strategy of the
+	 * mapper. See https://github.com/FasterXML/jackson-databind/issues/559 If such a
+	 * method will be provided below tests can be simplified.
+	 */
+
+	@Test
+	public void noCustomPropertyNamingStrategy() throws Exception {
+		this.context.register(JacksonAutoConfiguration.class);
+		this.context.refresh();
+		ObjectMapper mapper = this.context.getBean(ObjectMapper.class);
+		assertEquals("{\"propertyName\":null}", mapper.writeValueAsString(new Bar()));
+	}
+
+	@Test
+	public void customPropertyNamingStrategyCamelCaseToLowerCaseWithUnderscores()
+			throws Exception {
+		this.context.register(JacksonAutoConfiguration.class);
+		EnvironmentTestUtils
+				.addEnvironment(this.context,
+						"spring.jackson.property-naming-strategy:CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES");
+		this.context.refresh();
+		ObjectMapper mapper = this.context.getBean(ObjectMapper.class);
+		assertEquals("{\"property_name\":null}", mapper.writeValueAsString(new Bar()));
+	}
+
+	@Test
+	public void customPropertyNamingStrategyPascalCaseToCamelCase() throws Exception {
+		this.context.register(JacksonAutoConfiguration.class);
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"spring.jackson.property-naming-strategy:PASCAL_CASE_TO_CAMEL_CASE");
+		this.context.refresh();
+		ObjectMapper mapper = this.context.getBean(ObjectMapper.class);
+		assertEquals("{\"PropertyName\":null}", mapper.writeValueAsString(new Bar()));
+	}
+
+	@Test
+	public void customPropertyNamingStrategyLowerCase() throws Exception {
+		this.context.register(JacksonAutoConfiguration.class);
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"spring.jackson.property-naming-strategy:LOWER_CASE");
+		this.context.refresh();
+		ObjectMapper mapper = this.context.getBean(ObjectMapper.class);
+		assertEquals("{\"propertyname\":null}", mapper.writeValueAsString(new Bar()));
+	}
+
+	@Test
+	public void customPropertyNamingStrategyClass() throws Exception {
+		this.context.register(JacksonAutoConfiguration.class);
+		EnvironmentTestUtils
+				.addEnvironment(
+						this.context,
+						"spring.jackson.property-naming-strategy:com.fasterxml.jackson.databind.PropertyNamingStrategy.LowerCaseWithUnderscoresStrategy");
+		this.context.refresh();
+		ObjectMapper mapper = this.context.getBean(ObjectMapper.class);
+		assertEquals("{\"property_name\":null}", mapper.writeValueAsString(new Bar()));
+	}
+
 	@Test
 	public void enableSerializationFeature() throws Exception {
 		this.context.register(JacksonAutoConfiguration.class);
@@ -297,4 +406,16 @@ public class JacksonAutoConfigurationTests {
 
 	}
 
+	protected static class Bar {
+
+		private String propertyName;
+
+		public String getPropertyName() {
+			return this.propertyName;
+		}
+
+		public void setPropertyName(String propertyName) {
+			this.propertyName = propertyName;
+		}
+	}
 }

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

@@ -94,6 +94,8 @@ content into your application; rather pick only the properties that you need.
 	spring.resources.add-mappings=true # if default mappings should be added
 
 	# JACKSON ({sc-spring-boot-autoconfigure}}/jackson/JacksonProperties.{sc-ext}[JacksonProperties])
+	spring.jackson.date-format= # Date format string (e.g. yyyy-MM-dd HH:mm:ss), or a fully-qualified date format class name (e.g. com.fasterxml.jackson.databind.util.ISO8601DateFormat)
+	spring.jackson.property-naming-strategy= # One of the constants on Jackson's PropertyNamingStrategy (e.g. CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES) or the fully-qualified class name of a PropertyNamingStrategy subclass
 	spring.jackson.deserialization.*= # see Jackson's DeserializationFeature
 	spring.jackson.generator.*= # see Jackson's JsonGenerator.Feature
 	spring.jackson.mapper.*= # see Jackson's MapperFeature