Polishing.

Reorder methods and types. Rename MongoPersistentProperty.isOmitNullProperty to writeNullValues. Adapt caching MongoPersistentProperty and add tests.

Tweak Javadoc wording, add author and since tags.

See #3407
Original pull request: #3646.

Author: mp911de

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

@@ -103,6 +103,7 @@
  * @author Mark Paluch
  * @author Roman Puchkovskiy
  * @author Heesu Jung
+ * @author Divya Srivastava
  */
 public class MappingMongoConverter extends AbstractMongoConverter implements ApplicationContextAware {
 
@@ -737,20 +738,18 @@ private void writeProperties(Bson bson, MongoPersistentEntity<?> entity, Persist
 				continue;
 			}
 			if (prop.isAssociation()) {
+
 				writeAssociation(prop.getRequiredAssociation(), accessor, dbObjectAccessor);
 				continue;
 			}
 
 			Object value = accessor.getProperty(prop);
 
 			if (value == null) {
-				if(!prop.isPropertyOmittableOnNull()) {
-					writeSimpleInternal(value, bson , prop);
+				if (prop.writeNullValues()) {
+					dbObjectAccessor.put(prop, null);
 				}
-				continue;
-			}
-
-			if (!conversions.isSimpleType(value.getClass())) {
+			} else if (!conversions.isSimpleType(value.getClass())) {
 				writePropertyInternal(value, dbObjectAccessor, prop);
 			} else {
 				writeSimpleInternal(value, bson, prop);
@@ -763,7 +762,14 @@ private void writeAssociation(Association<MongoPersistentProperty> association,
 
 		MongoPersistentProperty inverseProp = association.getInverse();
 
-		writePropertyInternal(accessor.getProperty(inverseProp), dbObjectAccessor, inverseProp);
+		Object value = accessor.getProperty(inverseProp);
+
+		if (value == null && !inverseProp.isUnwrapped() && inverseProp.writeNullValues()) {
+			dbObjectAccessor.put(inverseProp, null);
+			return;
+		}
+
+		writePropertyInternal(value, dbObjectAccessor, inverseProp);
 	}
 
 	@SuppressWarnings({ "unchecked" })

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

@@ -41,6 +41,7 @@
  * @author Thomas Darimont
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Divya Srivastava
  */
 public class BasicMongoPersistentProperty extends AnnotationBasedPersistentProperty<MongoPersistentProperty>
 		implements MongoPersistentProperty {
@@ -214,6 +215,19 @@ public int getFieldOrder() {
 		return annotation != null ? annotation.order() : Integer.MAX_VALUE;
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.mapping.MongoPersistentProperty#skipNullValues()
+	 */
+	@Override
+	public boolean writeNullValues() {
+
+		org.springframework.data.mongodb.core.mapping.Field annotation = findAnnotation(
+				org.springframework.data.mongodb.core.mapping.Field.class);
+
+		return annotation != null && annotation.write() == Field.Write.ALWAYS;
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mapping.model.AbstractPersistentProperty#createAssociation()
@@ -286,17 +300,4 @@ public boolean isTextScoreProperty() {
 		return isAnnotationPresent(TextScore.class);
 	}
 
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.mapping.MongoPersistentProperty#isPropertyOmittableOnNull()
-	 */
-	public boolean isPropertyOmittableOnNull() {
-		org.springframework.data.mongodb.core.mapping.Field annotation = findAnnotation(
-				org.springframework.data.mongodb.core.mapping.Field.class);
-
-		if ( annotation != null && annotation.write().equals(Field.Write.ALWAYS) ) {
-			return false;
-		}
-		return true;
-	}
 }

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

@@ -33,6 +33,7 @@ public class CachingMongoPersistentProperty extends BasicMongoPersistentProperty
 	private boolean dbRefResolved;
 	private @Nullable DBRef dbref;
 	private @Nullable String fieldName;
+	private @Nullable Boolean writeNullValues;
 	private @Nullable Class<?> fieldType;
 	private @Nullable Boolean usePropertyAccess;
 	private @Nullable Boolean isTransient;
@@ -90,6 +91,20 @@ public String getFieldName() {
 		return this.fieldName;
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.mapping.BasicMongoPersistentProperty#skipNullValues()
+	 */
+	@Override
+	public boolean writeNullValues() {
+
+		if (this.writeNullValues == null) {
+			this.writeNullValues = super.writeNullValues();
+		}
+
+		return this.writeNullValues;
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.mapping.BasicMongoPersistentProperty#getFieldType()

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

@@ -28,27 +28,13 @@
  *
  * @author Oliver Gierke
  * @author Christoph Strobl
+ * @author Divya Srivastava
  */
 @Documented
 @Retention(RetentionPolicy.RUNTIME)
 @Target({ ElementType.FIELD, ElementType.METHOD, ElementType.ANNOTATION_TYPE })
 public @interface Field {
 
-	/**
-	 * Enumeration of write strategies for a field with null value.It decides whether a field with null value has to be
-	 * written to the resulting document to be saved to the database.
-	 */
-	enum Write{
-		/*
-		 * The field will always be written to the database irrespective of null value.
-		 */
-		ALWAYS,
-		/*
-		 * The field will only be written to the database if it has a non null value.
-		 */
-		NON_NULL
-	}
-
 	/**
 	 * The key to be used to store the field inside the document. Alias for {@link #name()}.
 	 *
@@ -82,12 +68,32 @@ enum Write{
 	FieldType targetType() default FieldType.IMPLICIT;
 
 	/**
-	 * If set to {@link Write#NON_NULL} {@literal null} values will be omitted.
-	 * Setting the value to {@link Write#ALWAYS} explicitly adds an entry for the given field
-	 * holding {@literal null} as a value {@code 'fieldName' : null }.
+	 * Write rules when to include a property value upon conversion. If set to {@link Write#NON_NULL} (default)
+	 * {@literal null} values are not written to the target {@code Document}. Setting the value to {@link Write#ALWAYS}
+	 * explicitly adds an entry for the given field holding {@literal null} as a value {@code 'fieldName' : null }.
 	 * <p />
-	 * <strong>NOTE</strong> Setting the value to {@link Write#ALWAYS} may lead to increased document size.
+	 * <strong>NOTE</strong>Setting the value to {@link Write#ALWAYS} may lead to increased document size.
+	 *
 	 * @return {@link Write#NON_NULL} by default.
+	 * @since 3.3
 	 */
 	Write write() default Write.NON_NULL;
+
+	/**
+	 * Enumeration of write strategies to define when a property is included for write conversion.
+	 *
+	 * @since 3.3
+	 */
+	enum Write {
+
+		/**
+		 * Value that indicates that property is to be always included, independent of value of the property.
+		 */
+		ALWAYS,
+
+		/**
+		 * Value that indicates that only properties with non-{@literal null} values are to be included.
+		 */
+		NON_NULL
+	}
 }

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

@@ -28,6 +28,7 @@
  * @author Patryk Wasik
  * @author Thomas Darimont
  * @author Christoph Strobl
+ * @author Divya Srivastava
  */
 public interface MongoPersistentProperty extends PersistentProperty<MongoPersistentProperty> {
 
@@ -54,6 +55,15 @@ public interface MongoPersistentProperty extends PersistentProperty<MongoPersist
 	 */
 	int getFieldOrder();
 
+	/**
+	 * Returns whether the property should be written to the database if its value is {@literal null}.
+	 *
+	 * @return
+	 * @since 3.3
+	 * @see Field.Write
+	 */
+	boolean writeNullValues();
+
 	/**
 	 * Returns whether the property is a {@link com.mongodb.DBRef}. If this returns {@literal true} you can expect
 	 * {@link #getDBRef()} to return an non-{@literal null} value.
@@ -104,24 +114,6 @@ public interface MongoPersistentProperty extends PersistentProperty<MongoPersist
 	 * @since 1.6
 	 */
 	boolean isTextScoreProperty();
-	
-	/**
-	 * Returns whether the property is to be written to the document if the value is null <br/>
-	 * It's annotated with {@link Field.Write}.
-	 *
-	 * @return
-	 * @since 1.6
-	 */
-	boolean isPropertyOmittableOnNull(); 
-
-	/**
-	 * Returns whether the property is to be written to the document if the value is null <br/>
-	 * It's annotated with {@link omitNull}.
-	 *
-	 * @return
-	 * @since 1.6
-	 */
-	boolean isOmitNullProperty(); 
 
 	/**
 	 * Returns the {@link DBRef} if the property is a reference.

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

@@ -63,6 +63,11 @@ public int getFieldOrder() {
 		return delegate.getFieldOrder();
 	}
 
+	@Override
+	public boolean writeNullValues() {
+		return delegate.writeNullValues();
+	}
+
 	@Override
 	public boolean isDbReference() {
 		return delegate.isDbReference();
@@ -92,11 +97,6 @@ public boolean isExplicitLanguageProperty() {
 	public boolean isTextScoreProperty() {
 		return delegate.isTextScoreProperty();
 	}
-	
-	@Override
-	public boolean isOmitNullProperty() {
-		return delegate.isOmitNullProperty();
-	}
 
 	@Override
 	@Nullable
@@ -321,8 +321,4 @@ public <T> PersistentPropertyAccessor<T> getAccessorForOwner(T owner) {
 		return delegate.getAccessorForOwner(owner);
 	}
 
-	@Override
-	public boolean isPropertyOmittableOnNull() {
-		return delegate.isPropertyOmittableOnNull();
-	}
 }