Register jackson-datatype-jdk7 module when using Java 7

Issue: SPR-13354

build.gradle

@@ -730,6 +730,7 @@ project("spring-web") {
 			exclude group: "org.apache.taglibs", module: "taglibs-standard-spec"
 		}
 		testCompile("com.fasterxml.jackson.datatype:jackson-datatype-joda:${jackson2Version}")
+		testCompile("com.fasterxml.jackson.datatype:jackson-datatype-jdk7:${jackson2Version}")
 		testCompile("com.fasterxml.jackson.datatype:jackson-datatype-jdk8:${jackson2Version}")
 		testRuntime("com.sun.mail:javax.mail:${javamailVersion}")
 	}

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

@@ -663,6 +663,18 @@ public class Jackson2ObjectMapperBuilder {
 
 	@SuppressWarnings("unchecked")
 	private void registerWellKnownModulesIfAvailable(ObjectMapper objectMapper) {
+		// Java 7 java.nio.file.Path class present?
+		if (ClassUtils.isPresent("java.nio.file.Path", this.moduleClassLoader)) {
+			try {
+				Class<? extends Module> jdk7Module = (Class<? extends Module>)
+						ClassUtils.forName("com.fasterxml.jackson.datatype.jdk7.Jdk7Module", this.moduleClassLoader);
+				objectMapper.registerModule(BeanUtils.instantiate(jdk7Module));
+			}
+			catch (ClassNotFoundException ex) {
+				// jackson-datatype-jdk7 not available
+			}
+		}
+
 		// Java 8 java.util.Optional class present?
 		if (ClassUtils.isPresent("java.util.Optional", this.moduleClassLoader)) {
 			try {

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

@@ -18,6 +18,8 @@ package org.springframework.http.converter.json;
 
 import java.io.IOException;
 import java.io.UnsupportedEncodingException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.text.SimpleDateFormat;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -244,6 +246,9 @@ public class Jackson2ObjectMapperBuilderTests {
 		DateTime dateTime = new DateTime(timestamp, DateTimeZone.UTC);
 		assertEquals(timestamp.toString(), new String(objectMapper.writeValueAsBytes(dateTime), "UTF-8"));
 
+		Path file = Paths.get("foo");
+		assertEquals("\"foo\"", new String(objectMapper.writeValueAsBytes(file), "UTF-8"));
+
 		Optional<String> optional = Optional.of("test");
 		assertEquals("\"test\"", new String(objectMapper.writeValueAsBytes(optional), "UTF-8"));
 	}