DATAMONGO-553 - MappingMongoConverter now uses MongoPersistentProperty.usePropertyAccess() to decide whether to use property access.

Introduced usePropertyAccess() method on MongoPersistentProperty and added an implementation that forces that into being true for Throwable.cause as using the field would cause a cycle as it points to this in the first place but rather massages the value in the getter.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/MappingMongoConverter.java

@@ -346,13 +346,14 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 
 		final BeanWrapper<MongoPersistentEntity<Object>, Object> wrapper = BeanWrapper.create(obj, conversionService);
-
-		// Write the ID
 		final MongoPersistentProperty idProperty = entity.getIdProperty();
+
 		if (!dbo.containsField("_id") && null != idProperty) {
 
+			boolean fieldAccessOnly = idProperty.usePropertyAccess() ? false : useFieldAccessOnly;
+
 			try {
-				Object id = wrapper.getProperty(idProperty, Object.class, useFieldAccessOnly);
+				Object id = wrapper.getProperty(idProperty, Object.class, fieldAccessOnly);
 				dbo.put("_id", idMapper.convertId(id));
 			} catch (ConversionException ignored) {
 			}
@@ -366,7 +367,9 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 					return;
 				}
 
-				Object propertyObj = wrapper.getProperty(prop, prop.getType(), useFieldAccessOnly);
+				boolean fieldAccessOnly = prop.usePropertyAccess() ? false : useFieldAccessOnly;
+
+				Object propertyObj = wrapper.getProperty(prop, prop.getType(), fieldAccessOnly);
 
 				if (null != propertyObj) {
 					if (!conversions.isSimpleType(propertyObj.getClass())) {

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentProperty.java

@@ -27,6 +27,7 @@ import org.slf4j.LoggerFactory;
 import org.springframework.data.mapping.Association;
 import org.springframework.data.mapping.model.AnnotationBasedPersistentProperty;
 import org.springframework.data.mapping.model.SimpleTypeHolder;
+import org.springframework.util.ReflectionUtils;
 import org.springframework.util.StringUtils;
 
 import com.mongodb.DBObject;
@@ -46,6 +47,8 @@ public class BasicMongoPersistentProperty extends AnnotationBasedPersistentPrope
 	private static final Set<Class<?>> SUPPORTED_ID_TYPES = new HashSet<Class<?>>();
 	private static final Set<String> SUPPORTED_ID_PROPERTY_NAMES = new HashSet<String>();
 
+	private static final Field CAUSE_FIELD;
+
 	static {
 		SUPPORTED_ID_TYPES.add(ObjectId.class);
 		SUPPORTED_ID_TYPES.add(String.class);
@@ -53,6 +56,8 @@ public class BasicMongoPersistentProperty extends AnnotationBasedPersistentPrope
 
 		SUPPORTED_ID_PROPERTY_NAMES.add("id");
 		SUPPORTED_ID_PROPERTY_NAMES.add("_id");
+
+		CAUSE_FIELD = ReflectionUtils.findField(Throwable.class, "cause");
 	}
 
 	/**
@@ -155,4 +160,12 @@ public class BasicMongoPersistentProperty extends AnnotationBasedPersistentPrope
 	public boolean isVersionProperty() {
 		return getField().isAnnotationPresent(Version.class);
 	}
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.mapping.MongoPersistentProperty#usePropertyAccess()
+	 */
+	public boolean usePropertyAccess() {
+		return CAUSE_FIELD.equals(getField());
+	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/MongoPersistentProperty.java

@@ -80,4 +80,12 @@ public interface MongoPersistentProperty extends PersistentProperty<MongoPersist
 			return source.getFieldName();
 		}
 	}
+
+	/**
+	 * Returns whether property access shall be used for reading the property value. This means it will use the getter
+	 * instead of field access.
+	 * 
+	 * @return
+	 */
+	boolean usePropertyAccess();
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/SimpleMongoMappingContext.java

@@ -123,6 +123,13 @@ public class SimpleMongoMappingContext extends
 			return false;
 		}
 
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.mapping.MongoPersistentProperty#usePropertyAccess()
+		 */
+		public boolean usePropertyAccess() {
+			return false;
+		}
 	}
 
 	static class SimpleMongoPersistentEntity<T> extends BasicPersistentEntity<T, MongoPersistentProperty> implements

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/MappingMongoConverterUnitTests.java

@@ -918,7 +918,7 @@ public class MappingMongoConverterUnitTests {
 		Object contacts = result.get("contacts");
 		assertThat(contacts, is(instanceOf(Collection.class)));
 		assertThat(((Collection<?>) contacts).size(), is(2));
-		assertThat(((Collection<Object>) contacts), hasItem(nullValue()));
+		assertThat((Collection<Object>) contacts, hasItem(nullValue()));
 	}
 
 	/**
@@ -1310,6 +1310,19 @@ public class MappingMongoConverterUnitTests {
 		assertThat(type.toString(), is("_"));
 	}
 
+	/**
+	 * @see DATAMONGO-533
+	 */
+	@Test
+	public void marshalsThrowableCorrectly() {
+
+		ThrowableWrapper wrapper = new ThrowableWrapper();
+		wrapper.throwable = new Exception();
+
+		DBObject dbObject = new BasicDBObject();
+		converter.write(wrapper, dbObject);
+	}
+
 	static class GenericType<T> {
 		T content;
 	}
@@ -1498,6 +1511,11 @@ public class MappingMongoConverterUnitTests {
 		String name;
 	}
 
+	static class ThrowableWrapper {
+
+		Throwable throwable;
+	}
+
 	private class LocalDateToDateConverter implements Converter<LocalDate, Date> {
 
 		public Date convert(LocalDate source) {

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentPropertyUnitTests.java

@@ -68,6 +68,16 @@ public class BasicMongoPersistentPropertyUnitTests {
 		getPropertyFor(ReflectionUtils.findField(Person.class, "ssn"));
 	}
 
+	/**
+	 * @see DATAMONGO-553
+	 */
+	@Test
+	public void usesPropertyAccessForThrowableCause() {
+
+		MongoPersistentProperty property = getPropertyFor(ReflectionUtils.findField(Throwable.class, "cause"));
+		assertThat(property.usePropertyAccess(), is(true));
+	}
+
 	private MongoPersistentProperty getPropertyFor(Field field) {
 		return new BasicMongoPersistentProperty(field, null, entity, new SimpleTypeHolder());
 	}