DATAMONGO-1798 - Polishing.

Introduce FieldType to express the desired field type to use for MongoDB Id conversion. Adapt Querydsl Id conversion so Id values are converted in the QueryMapper and no longer in SpringDataMongodbSerializer.

Adapt tests. Move MongoId from o.s.d.mongodb to o.s.d.m.c.core. Javadoc, reference docs.

Original pull request: #617.

Author: mp911de

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

@@ -517,7 +517,7 @@ protected void writeInternal(@Nullable Object obj, Bson bson, @Nullable MongoPer
 
 		if (idProperty != null && !dbObjectAccessor.hasValue(idProperty)) {
 
-			Object value = idMapper.convertId(accessor.getProperty(idProperty), idProperty.getIdType());
+			Object value = idMapper.convertId(accessor.getProperty(idProperty), idProperty.getFieldType());
 
 			if (value != null) {
 				dbObjectAccessor.put(idProperty, value);
@@ -982,7 +982,8 @@ protected DBRef createDBRef(Object target, MongoPersistentProperty property) {
 				throw new MappingException("Cannot create a reference to an object with a NULL id.");
 			}
 
-			return dbRefResolver.createDbRef(property == null ? null : property.getDBRef(), entity, idMapper.convertId(id, idProperty != null ? idProperty.getIdType() : ObjectId.class));
+			return dbRefResolver.createDbRef(property == null ? null : property.getDBRef(), entity,
+					idMapper.convertId(id, idProperty != null ? idProperty.getFieldType() : ObjectId.class));
 		}
 
 		throw new MappingException("No id property found on class " + entity.getType());

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

@@ -89,8 +89,8 @@ default <S, T> T mapValueToTargetType(S source, Class<T> targetType, DbRefResolv
 					String collection = sourceDocument.getString("$ref");
 
 					MongoPersistentEntity<?> entity = getMappingContext().getPersistentEntity(targetType);
-					if (entity.getIdType() != null) {
-						id = convertId(id, entity.getIdType());
+					if (entity != null && entity.hasIdProperty()) {
+						id = convertId(id, entity.getIdProperty().getFieldType());
 					}
 
 					DBRef ref = sourceDocument.containsKey("$db") ? new DBRef(sourceDocument.getString("$db"), collection, id)
@@ -120,6 +120,7 @@ default <S, T> T mapValueToTargetType(S source, Class<T> targetType, DbRefResolv
 	 * Converts the given raw id value into either {@link ObjectId} or {@link String}.
 	 *
 	 * @param id
+	 * @param targetType
 	 * @return {@literal null} if source {@literal id} is already {@literal null}.
 	 * @since 2.2
 	 */
@@ -142,7 +143,8 @@ default Object convertId(@Nullable Object id, Class<?> targetType) {
 
 		try {
 			return getConversionService().canConvert(id.getClass(), targetType)
-					? getConversionService().convert(id, targetType) : convertToMongoType(id, null);
+					? getConversionService().convert(id, targetType)
+					: convertToMongoType(id, null);
 		} catch (ConversionException o_O) {
 			return convertToMongoType(id, null);
 		}

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

@@ -244,7 +244,16 @@ protected Entry<String, Object> getMappedObjectForField(Field field, Object rawV
 	 */
 	protected Field createPropertyField(@Nullable MongoPersistentEntity<?> entity, String key,
 			MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext) {
-		return entity == null ? new Field(key) : new MetadataBackedField(key, entity, mappingContext);
+
+		if (entity == null) {
+			return new Field(key);
+		}
+
+		if (Field.ID_KEY.equals(key)) {
+			return new MetadataBackedField(key, entity, mappingContext, entity.getIdProperty());
+		}
+
+		return new MetadataBackedField(key, entity, mappingContext);
 	}
 
 	/**
@@ -372,7 +381,7 @@ private boolean isIdField(Field documentField) {
 	}
 
 	private Class<?> getIdTypeForField(Field documentField) {
-		return isIdField(documentField) ? documentField.getProperty().getIdType() : ObjectId.class;
+		return isIdField(documentField) ? documentField.getProperty().getFieldType() : ObjectId.class;
 	}
 
 	/**
@@ -477,7 +486,7 @@ protected Object convertAssociation(@Nullable Object source, @Nullable MongoPers
 
 			DBRef ref = (DBRef) source;
 			Object id = convertId(ref.getId(),
-					property != null && property.isIdProperty() ? property.getIdType() : ObjectId.class);
+					property != null && property.isIdProperty() ? property.getFieldType() : ObjectId.class);
 
 			if (StringUtils.hasText(ref.getDatabaseName())) {
 				return new DBRef(ref.getDatabaseName(), ref.getCollectionName(), id);
@@ -572,9 +581,10 @@ public Object convertId(@Nullable Object id) {
 	}
 
 	/**
-	 * Converts the given raw id value into either {@link ObjectId} or {@literal targetType}.
+	 * Converts the given raw id value into either {@link ObjectId} or {@link Class targetType}.
 	 *
 	 * @param id can be {@literal null}.
+	 * @param targetType
 	 * @return the converted {@literal id} or {@literal null} if the source was already {@literal null}.
 	 * @since 2.2
 	 */

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

@@ -67,8 +67,7 @@ public class BasicMongoPersistentProperty extends AnnotationBasedPersistentPrope
 	/**
 	 * Creates a new {@link BasicMongoPersistentProperty}.
 	 *
-	 * @param field
-	 * @param propertyDescriptor
+	 * @param property
 	 * @param owner
 	 * @param simpleTypeHolder
 	 * @param fieldNamingStrategy
@@ -144,6 +143,32 @@ public String getFieldName() {
 		return fieldName;
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.mapping.MongoPersistentProperty#getFieldType()
+	 */
+	@Override
+	public Class<?> getFieldType() {
+
+		if (!isIdProperty()) {
+			return getType();
+		}
+
+		MongoId idAnnotation = findAnnotation(MongoId.class);
+
+		if (idAnnotation == null) {
+			return FieldType.OBJECT_ID.getJavaClass();
+		}
+
+		FieldType fieldType = idAnnotation.targetType();
+
+		if (fieldType == FieldType.IMPLICIT) {
+			return getType();
+		}
+
+		return fieldType.getJavaClass();
+	}
+
 	/**
 	 * @return true if {@link org.springframework.data.mongodb.core.mapping.Field} having non blank
 	 *         {@link org.springframework.data.mongodb.core.mapping.Field#value()} present.

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

@@ -33,6 +33,7 @@ public class CachingMongoPersistentProperty extends BasicMongoPersistentProperty
 	private @Nullable boolean dbRefResolved;
 	private @Nullable DBRef dbref;
 	private @Nullable String fieldName;
+	private @Nullable Class<?> fieldType;
 	private @Nullable Boolean usePropertyAccess;
 	private @Nullable Boolean isTransient;
 
@@ -89,6 +90,20 @@ public String getFieldName() {
 		return this.fieldName;
 	}
 
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.mapping.BasicMongoPersistentProperty#getFieldType()
+	 */
+	@Override
+	public Class<?> getFieldType() {
+
+		if (this.fieldType == null) {
+			this.fieldType = super.getFieldType();
+		}
+
+		return this.fieldType;
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mapping.model.AnnotationBasedPersistentProperty#usePropertyAccess()

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

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2018 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.mongodb.core.mapping;
+
+import org.bson.types.ObjectId;
+
+/**
+ * Enumeration of field value types that can be used to represent a {@link org.bson.Document} field value. This
+ * enumeration contains a subset of {@link org.bson.BsonType} that is supported by the mapping and conversion
+ * components.
+ * <p/>
+ * Bson types are identified by a {@code byte} {@link #getBsonType() value}. This enumeration typically returns the
+ * according bson type value except for {@link #IMPLICIT} which is a marker to derive the field type from a property.
+ * 
+ * @author Mark Paluch
+ * @since 2.2
+ * @see org.bson.BsonType
+ */
+public enum FieldType {
+
+	/**
+	 * Implicit type that is derived from the property value.
+	 */
+	IMPLICIT(-1, Object.class), STRING(2, String.class), OBJECT_ID(7, ObjectId.class);
+
+	private final int bsonType;
+	private final Class<?> javaClass;
+
+	FieldType(int bsonType, Class<?> javaClass) {
+
+		this.bsonType = bsonType;
+		this.javaClass = javaClass;
+	}
+
+	/**
+	 * Returns the BSON type identifier. Can be {@code -1} if {@link FieldType} maps to a synthetic Bson type.
+	 * 
+	 * @return the BSON type identifier. Can be {@code -1} if {@link FieldType} maps to a synthetic Bson type.
+	 */
+	public int getBsonType() {
+		return bsonType;
+	}
+
+	/**
+	 * Returns the Java class used to represent the type.
+	 * 
+	 * @return the Java class used to represent the type.
+	 */
+	public Class<?> getJavaClass() {
+		return javaClass;
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/MongoId.java renamed to spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/MongoId.java

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.springframework.data.mongodb;
+package org.springframework.data.mongodb.core.mapping;
 
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
@@ -24,14 +24,16 @@
 import org.springframework.data.annotation.Id;
 
 /**
- * {@link MongoId} represents a MongoDB specific {@link Id} annotation that allows tweaking {@literal id} conversion. By
- * default {@link Object Class<Object>} will be used as the {@literal id's} target type. This means that the
- * actual property value is used. No conversion attempts to any other type is made. <br />
+ * {@link MongoId} represents a MongoDB specific {@link Id} annotation that allows customizing {@literal id} conversion.
+ * Id properties use {@link org.springframework.data.mongodb.core.mapping.FieldType#IMPLICIT} as the default
+ * {@literal id's} target type. This means that the actual property value is used. No conversion attempts to any other
+ * type are made. <br />
  * In contrast to {@link Id &#64;Id}, {@link String} {@literal id's} are stored as the such even when the actual value
  * represents a valid {@link org.bson.types.ObjectId#isValid(String) ObjectId hex String}. To trigger {@link String} to
- * {@link org.bson.types.ObjectId} conversion use {@link MongoId#targetType() &#64;MongoId(ObjectId.class)}.
+ * {@link org.bson.types.ObjectId} conversion use {@link MongoId#targetType() &#64;MongoId(FieldType.OBJECT_ID)}.
  *
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 2.2
  */
 @Id
@@ -44,16 +46,16 @@
 	 * @see #targetType()
 	 */
 	@AliasFor("targetType")
-	Class<?> value() default Object.class;
+	FieldType value() default FieldType.IMPLICIT;
 
 	/**
-	 * Get the preferred {@literal _id} type to be used. Defaulted to {@link Object Class&lt;Object&gt;} which used the
-	 * property's type. If defined different, the given value is attempted to be converted into the desired target type
-	 * via {@link org.springframework.data.mongodb.core.convert.MongoConverter#convertId(Object, Class)}.
+	 * Get the preferred {@literal _id} type to be used. Defaults to {@link FieldType#IMPLICIT} which uses the property's
+	 * type. If defined different, the given value is attempted to be converted into the desired target type via
+	 * {@link org.springframework.data.mongodb.core.convert.MongoConverter#convertId(Object, Class)}.
 	 *
-	 * @return the preferred {@literal id} type. {@link Object Class&lt;Object&gt;} by default.
+	 * @return the preferred {@literal id} type. {@link FieldType#IMPLICIT} by default.
 	 */
 	@AliasFor("value")
-	Class<?> targetType() default Object.class;
+	FieldType targetType() default FieldType.IMPLICIT;
 
 }

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

@@ -59,20 +59,4 @@ public interface MongoPersistentEntity<T> extends PersistentEntity<T, MongoPersi
 	 */
 	boolean hasTextScoreProperty();
 
-	/**
-	 * Returns the entities {@literal id} type of {@literal null} if the entity has no {@literal id} property.
-	 *
-	 * @return {@literal null} if the entity does not have an {@link #hasIdProperty() id property}.
-	 * @since 2.2
-	 */
-	@Nullable
-	default Class<?> getIdType() {
-
-		if (!hasIdProperty()) {
-			return null;
-		}
-
-		return getIdProperty().getIdType();
-	}
-
 }

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

@@ -15,12 +15,10 @@
  */
 package org.springframework.data.mongodb.core.mapping;
 
-import org.bson.types.ObjectId;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.annotation.Id;
 import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.PersistentProperty;
-import org.springframework.data.mongodb.MongoId;
 import org.springframework.lang.Nullable;
 
 /**
@@ -40,6 +38,15 @@ public interface MongoPersistentProperty extends PersistentProperty<MongoPersist
 	 */
 	String getFieldName();
 
+	/**
+	 * Returns the {@link Class Java FieldType} of the field a property is persisted to.
+	 *
+	 * @return
+	 * @since 2.2
+	 * @see FieldType
+	 */
+	Class<?> getFieldType();
+
 	/**
 	 * Returns the order of the field if defined. Will return -1 if undefined.
 	 *
@@ -63,33 +70,6 @@ public interface MongoPersistentProperty extends PersistentProperty<MongoPersist
 	 */
 	boolean isExplicitIdProperty();
 
-	/**
-	 * Get the target id type to be used when writing the actual id value.
-	 *
-	 * @return The properties actual type of {@link Object Class&lt;Object&gt;} for properties using the native property
-	 *         type. <br />
-	 *         {@link org.bson.types.ObjectId Class&lt;ObjectId&gt;} indicates the attempt to parse the given raw value as
-	 *         {@link org.bson.types.ObjectId}.
-	 * @throws IllegalStateException if the property is not considered an id property. Please make sure to check
-	 *           {@link #isIdProperty()}.
-	 * @since 2.2
-	 */
-	default Class<?> getIdType() {
-
-		if (!isIdProperty()) {
-
-			throw new IllegalStateException(String.format("Property '%s' is not considerd an 'id' property",
-					getField() != null ? getField().getName() : getFieldName()));
-		}
-
-		MongoId idAnnotation = findAnnotation(MongoId.class);
-		if (idAnnotation == null) {
-			return ObjectId.class;
-		}
-
-		return Object.class.equals(idAnnotation.targetType()) ? getActualType() : idAnnotation.targetType();
-	}
-
 	/**
 	 * Returns true whether the property indicates the documents language either by having a {@link #getFieldName()} equal
 	 * to {@literal language} or being annotated with {@link Language}.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/SpringDataMongodbSerializer.java

@@ -120,28 +120,9 @@ protected Document asDocument(@Nullable String key, @Nullable Object value) {
 
 		value = value instanceof Optional ? ((Optional) value).orElse(null) : value;
 
-		if (ID_KEY.equals(key) || (key != null && key.endsWith("." + ID_KEY))) {
-			return convertId(key, value);
-		}
-
 		return super.asDocument(key, value instanceof Pattern ? value : converter.convertToMongoType(value));
 	}
 
-	/**
-	 * Convert a given, already known to be an {@literal id} or even a nested document id, value into the according id
-	 * representation following the conversion rules of {@link QueryMapper#convertId(Object)}.
-	 *
-	 * @param key the property path to the given value.
-	 * @param idValue the raw {@literal id} value.
-	 * @return the {@literal id} representation in the required format.
-	 */
-	private Document convertId(String key, Object idValue) {
-
-		Object convertedId = mapper.convertId(idValue);
-
-		return mapper.getMappedObject(super.asDocument(key, convertedId), Optional.empty());
-	}
-
 	/*
 	 * (non-Javadoc)
 	 * @see com.querydsl.mongodb.MongodbSerializer#isReference(com.querydsl.core.types.Path)