DATAREST-1321 - Lookup types can now produce non-String reference values.

Previously we assumed lookup types to always result in String based values. We now loosen that constraint to also allow other scalar types, mostly targeting numeric types like long and integer.

Author: odrotbohm

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

@@ -763,7 +763,10 @@ private RepositoryInvokingDeserializer(RepositoryInvokerFactory factory, Persist
 		 */
 		@Override
 		public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
-			return invoker.invokeFindById(p.getValueAsString());
+
+			Object id = p.getCurrentToken().isNumeric() ? p.getValueAsLong() : p.getValueAsString();
+
+			return invoker.invokeFindById(id).orElse(null);
 		}
 	}
 
@@ -785,23 +788,22 @@ public void serialize(Object value, JsonGenerator gen, SerializerProvider provid
 				gen.writeStartArray();
 
 				for (Object element : (Collection<?>) value) {
-					gen.writeString(getLookupKey(element));
+					gen.writeObject(getLookupKey(element));
 				}
 
 				gen.writeEndArray();
 
 			} else {
-				gen.writeString(getLookupKey(value));
+				gen.writeObject(getLookupKey(value));
 			}
 		}
 
-		private String getLookupKey(Object value) {
-
-			Optional<EntityLookup<Object>> map = lookups.getPluginFor(value.getClass()).map(CastUtils::cast);
+		private Object getLookupKey(Object value) {
 
-			return map
+			return lookups.getPluginFor(value.getClass()) //
+					.<EntityLookup<Object>> map(CastUtils::cast)
 					.orElseThrow(() -> new IllegalArgumentException("No EntityLookup found for " + value.getClass().getName()))
-					.getResourceIdentifier(value).toString();
+					.getResourceIdentifier(value);
 		}
 	}
 }

spring-data-rest-webmvc/src/test/java/org/springframework/data/rest/webmvc/json/PersistentEntityJackson2ModuleUnitTests.java

@@ -16,12 +16,16 @@
 package org.springframework.data.rest.webmvc.json;
 
 import static org.assertj.core.api.Assertions.*;
+import static org.mockito.ArgumentMatchers.*;
 import static org.mockito.Mockito.*;
 
+import lombok.Getter;
+
 import java.io.IOException;
 import java.net.URI;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.Optional;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -32,9 +36,11 @@
 import org.springframework.data.keyvalue.core.mapping.context.KeyValueMappingContext;
 import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.context.PersistentEntities;
+import org.springframework.data.repository.support.RepositoryInvoker;
 import org.springframework.data.repository.support.RepositoryInvokerFactory;
 import org.springframework.data.rest.core.UriToEntityConverter;
 import org.springframework.data.rest.core.mapping.ResourceMappings;
+import org.springframework.data.rest.core.support.EntityLookup;
 import org.springframework.data.rest.core.support.SelfLinkProvider;
 import org.springframework.data.rest.core.util.Java8PluginRegistry;
 import org.springframework.data.rest.webmvc.EmbeddedResourcesAssembler;
@@ -49,6 +55,8 @@
 import org.springframework.hateoas.UriTemplate;
 import org.springframework.hateoas.mvc.ResourceProcessorInvoker;
 
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonInclude.Include;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -69,6 +77,7 @@ public class PersistentEntityJackson2ModuleUnitTests {
 	@Mock EntityLinks entityLinks;
 	@Mock ResourceMappings mappings;
 	@Mock SelfLinkProvider selfLinks;
+	@Mock RepositoryInvokerFactory factory;
 
 	PersistentEntities persistentEntities;
 	ObjectMapper mapper;
@@ -90,9 +99,9 @@ public void setUp() {
 		SimpleModule module = new SimpleModule();
 
 		module.setSerializerModifier(new AssociationOmittingSerializerModifier(persistentEntities, associations,
-				nestedEntitySerializer, new LookupObjectSerializer(Java8PluginRegistry.empty())));
-		module.setDeserializerModifier(new AssociationUriResolvingDeserializerModifier(persistentEntities, associations,
-				converter, mock(RepositoryInvokerFactory.class)));
+				nestedEntitySerializer, new LookupObjectSerializer(Java8PluginRegistry.of(Arrays.asList(new HomeLookup())))));
+		module.setDeserializerModifier(
+				new AssociationUriResolvingDeserializerModifier(persistentEntities, associations, converter, factory));
 
 		this.mapper = new ObjectMapper();
 		this.mapper.registerModule(module);
@@ -135,20 +144,80 @@ public void resolvesReferenceToSubtypeCorrectly() throws IOException {
 		assertThat(petOwner.getPet()).isNotNull();
 	}
 
-	static class PetOwner {
+	@Test // DATAREST-1321
+	public void allowsNumericIdsForLookupTypes() throws Exception {
 
-		Pet pet;
+		RepositoryInvoker invoker = mock(RepositoryInvoker.class);
+		when(invoker.invokeFindById(any(Long.class))).thenReturn(Optional.of(new Home()));
+
+		when(factory.getInvokerFor(Home.class)).thenReturn(invoker);
+
+		PersistentProperty<?> property = persistentEntities.getRequiredPersistentEntity(PetOwner.class)
+				.getRequiredPersistentProperty("home");
+
+		when(associations.isLookupType(property)).thenReturn(true);
+
+		PetOwner petOwner = mapper.readValue("{\"home\": 1 }", PetOwner.class);
+
+		assertThat(petOwner).isNotNull();
+		assertThat(petOwner.getHome()).isInstanceOf(Home.class);
+	}
+
+	@Test // DATAREST-1321
+	public void serializesNonStringLookupValues() throws Exception {
+
+		// Given Pet defined as lookup type
+		PersistentProperty<?> property = persistentEntities.getRequiredPersistentEntity(PetOwner.class)
+				.getRequiredPersistentProperty("home");
+		when(associations.isLookupType(property)).thenReturn(true);
+
+		// When a Pet is rendered
+		PetOwner owner = new PetOwner();
+		owner.home = new Home();
 
-		public Pet getPet() {
-			return pet;
+		String result = mapper.writeValueAsString(owner);
+
+		// The it appears as numeric value
+		assertThat(JsonPath.parse(result).read("$.home", Integer.class)) //
+				.isEqualTo(41);
+	}
+
+	/**
+	 * @author Oliver Gierke
+	 */
+	private static class HomeLookup implements EntityLookup<Home> {
+
+		@Override
+		public Object getResourceIdentifier(Home entity) {
+			return 41;
+		}
+
+		@Override
+		public boolean supports(Class<?> delimiter) {
+			return delimiter.equals(Home.class);
+		}
+
+		@Override
+		public Optional<Home> lookupEntity(Object id) {
+			return Optional.of(new Home());
 		}
 	}
 
+	@Getter
+	@JsonInclude(Include.NON_NULL)
+	static class PetOwner {
+
+		Pet pet;
+		Home home;
+	}
+
 	@JsonTypeInfo(include = JsonTypeInfo.As.PROPERTY, use = JsonTypeInfo.Id.MINIMAL_CLASS)
 	static class Pet {}
 
 	static class Cat extends Pet {}
 
+	static class Home {}
+
 	static class Sample {
 		public @JsonProperty("foo") String name;
 	}