DATAREST-575 - Fixed property lookup in MappedProperties.

Previously, MappedProperties didn't handle Jackson properties correctly, that do not expose a PersistentProperty, e.g. transient ones. That led to potential nullPointerExceptions in clients as the guarding hasPersistentPropertyForField(…) still answered true, as the backing cache contained an entry with a null value. We now skip those properties completely.

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

@@ -49,6 +49,9 @@ class MappedProperties {
 	 */
 	private MappedProperties(PersistentEntity<?, ?> entity, BeanDescription description) {
 
+		Assert.notNull(entity, "Entity must not be null!");
+		Assert.notNull(description, "BeanDescription must not be null!");
+
 		this.propertyToFieldName = new HashMap<PersistentProperty<?>, String>();
 		this.fieldNameToProperty = new HashMap<String, PersistentProperty<?>>();
 
@@ -56,8 +59,10 @@ class MappedProperties {
 
 			PersistentProperty<?> persistentProperty = entity.getPersistentProperty(property.getInternalName());
 
-			propertyToFieldName.put(persistentProperty, property.getName());
-			fieldNameToProperty.put(property.getName(), persistentProperty);
+			if (persistentProperty != null) {
+				propertyToFieldName.put(persistentProperty, property.getName());
+				fieldNameToProperty.put(property.getName(), persistentProperty);
+			}
 		}
 	}
 
@@ -100,7 +105,7 @@ class MappedProperties {
 
 	/**
 	 * @param fieldName must not be empty or {@literal null}.
-	 * @return
+	 * @return the {@link PersistentProperty} backing the field with the field name.
 	 */
 	public PersistentProperty<?> getPersistentProperty(String fieldName) {
 

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

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.rest.webmvc.json;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+import org.springframework.data.annotation.Transient;
+import org.springframework.data.keyvalue.core.mapping.KeyValuePersistentEntity;
+import org.springframework.data.keyvalue.core.mapping.context.KeyValueMappingContext;
+
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+/**
+ * Unit tests for {@link MappedProperties}.
+ * 
+ * @author Oliver Gierke
+ */
+public class MappedPropertiesUnitTests {
+
+	ObjectMapper mapper = new ObjectMapper();
+	KeyValueMappingContext context = new KeyValueMappingContext();
+	KeyValuePersistentEntity<?> entity = context.getPersistentEntity(Sample.class);
+	MappedProperties properties = MappedProperties.fromJacksonProperties(entity, mapper);
+
+	/**
+	 * @see DATAREST-575
+	 */
+	@Test
+	public void doesNotExposeMappedPropertyForNonSpringDataPersistentProperty() {
+
+		assertThat(properties.hasPersistentPropertyForField("notExposedBySpringData"), is(false));
+		assertThat(properties.getPersistentProperty("notExposedBySpringData"), is(nullValue()));
+	}
+
+	/**
+	 * @see DATAREST-575
+	 */
+	@Test
+	public void doesNotExposeMappedPropertyForNonJacksonProperty() {
+
+		assertThat(properties.hasPersistentPropertyForField("notExposedByJackson"), is(false));
+		assertThat(properties.getPersistentProperty("notExposedByJackson"), is(nullValue()));
+	}
+
+	/**
+	 * @see DATAREST-575
+	 */
+	@Test
+	public void exposesProperty() {
+
+		assertThat(properties.hasPersistentPropertyForField("exposedProperty"), is(true));
+		assertThat(properties.getPersistentProperty("exposedProperty"), is(notNullValue()));
+	}
+
+	/**
+	 * @see DATAREST-575
+	 */
+	@Test
+	public void exposesRenamedPropertyByExternalName() {
+
+		assertThat(properties.hasPersistentPropertyForField("email"), is(true));
+		assertThat(properties.getPersistentProperty("email"), is(notNullValue()));
+		assertThat(properties.getMappedName(entity.getPersistentProperty("emailAddress")), is("email"));
+	}
+
+	static class Sample {
+
+		public @Transient String notExposedBySpringData;
+		public @JsonIgnore String notExposedByJackson;
+		public String exposedProperty;
+		public @JsonProperty("email") String emailAddress;
+	}
+}