DATAREST-864 - NestedEntitySerializer now handles Maps correctly.

Previously, NestedEntitySerializer failed to handle Maps correctly as the logic to convert the found values to nested resources tried to handle the values as is, not explicitly looking at the values instead.

We now use an explicit code path to turn the values into resources so that links pointing to other resources are rendered correctly.

Original pull request: spring-projects#219.

Author: odrotbohm

spring-data-rest-tests/spring-data-rest-tests-mongodb/src/main/java/org/springframework/data/rest/tests/mongodb/User.java

@@ -15,9 +15,13 @@
  */
 package org.springframework.data.rest.tests.mongodb;
 
+import lombok.Value;
+
 import java.math.BigInteger;
 import java.time.LocalDateTime;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 
 import org.springframework.data.annotation.ReadOnlyProperty;
@@ -47,6 +51,7 @@ public static enum Gender {
 	public org.joda.time.LocalDateTime jodaDateTime;
 	public TypeWithPattern pattern;
 	public @DBRef(lazy = true) List<User> colleagues;
+	public Map<String, Nested> colleaguesMap = new HashMap<String, Nested>();
 
 	public static class EmailAddress {
 
@@ -67,4 +72,10 @@ public String toString() {
 	}
 
 	public static class TypeWithPattern {}
+
+	@Value
+	public static class Nested {
+		public @DBRef(lazy = true) User user;
+		public String foo = "foo";
+	}
 }

spring-data-rest-tests/spring-data-rest-tests-mongodb/src/test/java/org/springframework/data/rest/webmvc/json/PersistentEntitySerializationTests.java

@@ -19,6 +19,7 @@
 import static org.hamcrest.Matchers.*;
 
 import java.util.Arrays;
+import java.util.HashMap;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -36,6 +37,8 @@
 import org.springframework.data.rest.tests.mongodb.MongoDbRepositoryConfig;
 import org.springframework.data.rest.tests.mongodb.User;
 import org.springframework.data.rest.tests.mongodb.User.Gender;
+import org.springframework.data.rest.tests.mongodb.User.Nested;
+import org.springframework.data.rest.tests.mongodb.UserRepository;
 import org.springframework.data.rest.webmvc.PersistentEntityResource;
 import org.springframework.hateoas.Link;
 import org.springframework.hateoas.LinkDiscoverer;
@@ -65,6 +68,7 @@ public class PersistentEntitySerializationTests {
 
 	@Autowired ObjectMapper mapper;
 	@Autowired Repositories repositories;
+	@Autowired UserRepository users;
 
 	@Configuration
 	static class TestConfig extends RepositoryTestsConfig {
@@ -122,4 +126,21 @@ public void serializesEmbeddedReferencesCorrectly() throws Exception {
 	public void deserializesTranslatedEnumProperty() throws Exception {
 		assertThat(mapper.readValue("{ \"gender\" : \"Male\" }", User.class).gender, is(Gender.MALE));
 	}
+
+	/**
+	 * @see DATAREST-864
+	 */
+	@Test
+	public void createsNestedResourceForMap() throws Exception {
+
+		User dave = users.save(new User());
+		dave.colleaguesMap = new HashMap<String, Nested>();
+		dave.colleaguesMap.put("carter", new Nested(users.save(new User())));
+
+		PersistentEntityResource resource = PersistentEntityResource
+				.build(dave, repositories.getPersistentEntity(User.class)).build();
+
+		assertThat(JsonPath.parse(mapper.writeValueAsString(resource)).read("$.colleaguesMap.carter._links.user.href",
+				String.class), is(notNullValue()));
+	}
 }

spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/json/PersistentEntityJackson2Module.java

@@ -24,6 +24,8 @@
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -351,6 +353,17 @@ public void serialize(Object value, JsonGenerator gen, SerializerProvider provid
 
 				provider.defaultSerializeValue(resources, gen);
 
+			} else if (value instanceof Map) {
+
+				Map<?, ?> source = (Map<?, ?>) value;
+				Map<Object, Object> resources = CollectionFactory.createMap(value.getClass(), source.size());
+
+				for (Entry<?, ?> entry : source.entrySet()) {
+					resources.put(entry.getKey(), toResource(entry.getValue()));
+				}
+
+				provider.defaultSerializeValue(resources, gen);
+
 			} else {
 				provider.defaultSerializeValue(toResource(value), gen);
 			}