Auto-detect Kotlin Jackson module

Issue: SPR-14108

Author: sdeleuze

build.gradle

@@ -739,6 +739,7 @@ project("spring-web") {
 		}
 		testCompile("com.fasterxml.jackson.datatype:jackson-datatype-joda:${jackson2Version}")
 		testCompile("com.fasterxml.jackson.datatype:jackson-datatype-jdk8:${jackson2Version}")
+		testCompile("com.fasterxml.jackson.module:jackson-module-kotlin:${jackson2Version}")
 		testRuntime("com.sun.mail:javax.mail:${javamailVersion}")
 	}
 }

spring-web/src/main/java/org/springframework/http/converter/json/Jackson2ObjectMapperBuilder.java

@@ -75,6 +75,7 @@
  * <li><a href="https://github.com/FasterXML/jackson-datatype-jdk8">jackson-datatype-jdk8</a>: support for other Java 8 types like {@link java.util.Optional}</li>
  * <li><a href="https://github.com/FasterXML/jackson-datatype-jsr310">jackson-datatype-jsr310</a>: support for Java 8 Date & Time API types</li>
  * <li><a href="https://github.com/FasterXML/jackson-datatype-joda">jackson-datatype-joda</a>: support for Joda-Time types</li>
+ * <li><a href="https://github.com/FasterXML/jackson-module-kotlin">jackson-module-kotlin</a>: support for Kotlin classes and data classes</li>
  * </ul>
  *
  * <p>Compatible with Jackson 2.6 and higher, as of Spring 4.3.
@@ -747,6 +748,18 @@ private void registerWellKnownModulesIfAvailable(ObjectMapper objectMapper) {
 				// jackson-datatype-joda not available
 			}
 		}
+
+		// Kotlin present?
+		if (ClassUtils.isPresent("kotlin.Unit", this.moduleClassLoader)) {
+			try {
+				Class<? extends Module> kotlinModule = (Class<? extends Module>)
+						ClassUtils.forName("com.fasterxml.jackson.module.kotlin.KotlinModule", this.moduleClassLoader);
+				objectMapper.registerModule(BeanUtils.instantiate(kotlinModule));
+			}
+			catch (ClassNotFoundException ex) {
+				// jackson-module-kotlin not available
+			}
+		}
 	}
 
 

spring-web/src/main/java/org/springframework/http/converter/json/Jackson2ObjectMapperFactoryBean.java

@@ -116,6 +116,7 @@
  * <li><a href="https://github.com/FasterXML/jackson-datatype-jdk8">jackson-datatype-jdk8</a>: support for other Java 8 types like {@link java.util.Optional}</li>
  * <li><a href="https://github.com/FasterXML/jackson-datatype-jsr310">jackson-datatype-jsr310</a>: support for Java 8 Date & Time API types</li>
  * <li><a href="https://github.com/FasterXML/jackson-datatype-joda">jackson-datatype-joda</a>: support for Joda-Time types</li>
+ * <li><a href="https://github.com/FasterXML/jackson-module-kotlin">jackson-module-kotlin</a>: support for Kotlin classes and data classes</li>
  * </ul>
  *
  * <p>In case you want to configure Jackson's {@link ObjectMapper} with a custom {@link Module},

spring-web/src/test/java/org/springframework/http/converter/json/Jackson2ObjectMapperBuilderTests.java

@@ -65,6 +65,7 @@
 import com.fasterxml.jackson.databind.type.SimpleType;
 import com.fasterxml.jackson.dataformat.xml.XmlMapper;
 
+import kotlin.ranges.IntRange;
 import org.joda.time.DateTime;
 import org.joda.time.DateTimeZone;
 import org.junit.Test;
@@ -255,6 +256,10 @@ public void wellKnownModules() throws JsonProcessingException, UnsupportedEncodi
 
 		Optional<String> optional = Optional.of("test");
 		assertEquals("\"test\"", new String(objectMapper.writeValueAsBytes(optional), "UTF-8"));
+
+		// Kotlin module
+		IntRange range = new IntRange(1, 3);
+		assertEquals("{\"start\":1,\"end\":3}", new String(objectMapper.writeValueAsBytes(range), "UTF-8"));
 	}
 
 	@Test // SPR-12634
@@ -328,8 +333,8 @@ public void mixIn() {
 		Class<?> target = String.class;
 		Class<?> mixInSource = Object.class;
 
-		ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json().mixIn(target,
-				mixInSource).build();
+		ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json().modules()
+				.mixIn(target, mixInSource).build();
 
 		assertEquals(1, objectMapper.mixInCount());
 		assertSame(mixInSource, objectMapper.findMixInClassFor(target));
@@ -342,7 +347,8 @@ public void mixIns() {
 		Map<Class<?>, Class<?>> mixIns = new HashMap<Class<?>, Class<?>>();
 		mixIns.put(target, mixInSource);
 
-		ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json().mixIns(mixIns).build();
+		ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json().modules()
+				.mixIns(mixIns).build();
 
 		assertEquals(1, objectMapper.mixInCount());
 		assertSame(mixInSource, objectMapper.findMixInClassFor(target));

spring-web/src/test/java/org/springframework/http/converter/json/Jackson2ObjectMapperFactoryBeanTests.java

@@ -285,6 +285,7 @@ public void setMixIns() {
 		Map<Class<?>, Class<?>> mixIns = new HashMap<Class<?>, Class<?>>();
 		mixIns.put(target, mixinSource);
 
+		this.factory.setModules(Collections.emptyList());
 		this.factory.setMixIns(mixIns);
 		this.factory.afterPropertiesSet();
 		ObjectMapper objectMapper = this.factory.getObject();