MappingMongoConverter problem: ConversionContext#convert does not try to use custom converters first

[xjme]

Hi, we upgraded from spring boot 2.4.3 to version 2.5.0. In the new version of SB, the spring data mongo db was updated from version 3.1.5 to 3.2.1.

We encountered a problem during the conversion of an object implementing java.util.Map, for which, however, we have implemented a custom converter.

The problem is that the custom converter is not called, the default mapConverter is used instead.

When I compare the previous code of MappingMongoConverter, more precisely code related to converting a property value, it was first checked whether a value with a certain type has a custom conversion defined. This is not the case in the new version of spring data mongodb, more precisely within ConversionContext#convert method.

For clarity, I present the differences between the individual versions of MappingMongoConvertor:

Spring Data MongoDb 3.2.1

MappingMongoConverter#getPropertyValue

@Nullable
@SuppressWarnings("unchecked")
public <T> T getPropertyValue(MongoPersistentProperty property) {

	String expression = property.getSpelExpression();
	Object value = expression != null ? evaluator.evaluate(expression) : accessor.get(property);

	if (value == null) {
		return null;
	}

	return (T) context.convert(value, property.getTypeInformation());
}

MappingMongoConverter.ConversionContext#convert

public <S extends Object> S convert(Object source, TypeInformation<? extends S> typeHint) {

	Assert.notNull(typeHint, "TypeInformation must not be null");

	if (source instanceof Collection) {

		Class<?> rawType = typeHint.getType();
		if (!Object.class.equals(rawType)) {
			if (!rawType.isArray() && !ClassUtils.isAssignable(Iterable.class, rawType)) {
				throw new MappingException(
						String.format(INCOMPATIBLE_TYPES, source, source.getClass(), rawType, getPath()));
			}
		}

		if (typeHint.isCollectionLike() || typeHint.getType().isAssignableFrom(Collection.class)) {
			return (S) collectionConverter.convert(this, (Collection<?>) source, typeHint);
		}
	}

	if (typeHint.isMap()) { // this causes a problem, it should be converted using custom map converter, not this.mapConverter
		return (S) mapConverter.convert(this, (Bson) source, typeHint);
	}

	if (source instanceof DBRef) {
		return (S) dbRefConverter.convert(this, (DBRef) source, typeHint);
	}

	if (source instanceof Collection) {
		throw new MappingException(
				String.format(INCOMPATIBLE_TYPES, source, BasicDBList.class, typeHint.getType(), getPath()));
	}

	if (source instanceof Bson) {
		return (S) documentConverter.convert(this, (Bson) source, typeHint);
	}

	return (S) elementConverter.convert(source, typeHint);
}

vs.

Spring Data MongoDb 3.1.5

MappingMongoConverter#getPropertyValue

@Nullable
public <T> T getPropertyValue(MongoPersistentProperty property) {

	String expression = property.getSpelExpression();
	Object value = expression != null ? evaluator.evaluate(expression) : accessor.get(property);

	if (value == null) {
		return null;
	}

	return readValue(value, property.getTypeInformation(), path);
}

MappingMongoConverter#readValue

@Nullable
@SuppressWarnings("unchecked")
<T> T readValue(Object value, TypeInformation<?> type, ObjectPath path) {

	Class<?> rawType = type.getType();

	if (conversions.hasCustomReadTarget(value.getClass(), rawType)) { // this check picks the custom converter
		return (T) conversionService.convert(value, rawType);
	} else if (value instanceof DBRef) {
		return potentiallyReadOrResolveDbRef((DBRef) value, type, path, rawType);
	} else if (value instanceof List) {
		return (T) readCollectionOrArray(type, (List<Object>) value, path);
	} else if (value instanceof Document) {
		return (T) read(type, (Document) value, path);
	} else if (value instanceof DBObject) {
		return (T) read(type, (BasicDBObject) value, path);
	} else {
		return (T) getPotentiallyConvertedSimpleRead(value, rawType);
	}
}

[christophstrobl]

thanks for reporting! we'll look into it.