@DocumentReference does not work as a drop-in replacement of @DBRef

[ntf]

Hi there,

I came across the new feature @DocumentReference as I was working on something that needs support of another new feature TimeSeries .

I was trying to use @DocumentReference on a new field as I want to store ["612cf1ef637b391363f1392e"] instead of the DbRef equivalent ["{ \"$ref\" : \"COLLECTION_NAME\", \"$id\" : \"612cf1ef637b391363f1392e\" }"]

Following the documentation here: https://docs.spring.io/spring-data/mongodb/docs/3.3.0-M2/reference/html/#mapping-usage.document-references

I thought I could use (Kotlin)

@DocumentReference(collection = "COLLECTION_NAME", lookup = "{ '_id' : ?#{#target} }")
var myList: List<MyListItem> = mutableListOf()

as a drop-in replacement of

@DBRef

But unfortunately it doesn't work as I expected.

I tried both MongoRepository and MongoTemplate and both complain about missing a converter from a String to MyListItem.

With the help of a debugger, I think it should be related to this block of code.

https://github.com/spring-projects/spring-data-mongodb/blob/3.3.0-M2/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/MappingMongoConverter.java#L2068

I was expecting there is a block of code similar to the DbRef that help resolving DocumentReference.

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

[christophstrobl]

From reading the description I cannot spot what exactly the issue might be, given that the tests, in MongoTemplateDocumentReferenceTests that should cover this, pass.
Do you have a minimal sample (something that we can unzip or git clone, build, and deploy) that reproduces the problem? This would help us identify the issue.

[ntf]

I crafted this example just now with Spring Initializr.

test-mongo-documentreference.zip

Attached belo MongoDb datatabase view on Intellij IDEA.

Caused by: org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [java.lang.String] to type [com.example.demo.models.Instrument]
at org.springframework.core.convert.support.GenericConversionService.handleConverterNotFound(GenericConversionService.java:322) ~[spring-core-5.3.9.jar:5.3.9]
at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:195) ~[spring-core-5.3.9.jar:5.3.9]
at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:175) ~[spring-core-5.3.9.jar:5.3.9]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.doConvert(MappingMongoConverter.java:1679) ~[spring-data-mongodb-3.3.0-M2.jar:3.3.0-M2]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.doConvert(MappingMongoConverter.java:1671) ~[spring-data-mongodb-3.3.0-M2.jar:3.3.0-M2]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.getPotentiallyConvertedSimpleRead(MappingMongoConverter.java:1192) ~[spring-data-mongodb-3.3.0-M2.jar:3.3.0-M2]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.getPotentiallyConvertedSimpleRead(MappingMongoConverter.java:1166) ~[spring-data-mongodb-3.3.0-M2.jar:3.3.0-M2]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter$ConversionContext.convert(MappingMongoConverter.java:2068) ~[spring-data-mongodb-3.3.0-M2.jar:3.3.0-M2]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readCollectionOrArray(MappingMongoConverter.java:1276) ~[spring-data-mongodb-3.3.0-M2.jar:3.3.0-M2]
at org.springframework.data.mongodb.core.convert.MappingMongoConverter$ConversionContext.convert(MappingMongoConverter.java:2038) ~[spring-data-mongodb-3.3.0-M2.jar:3.3.0-M2]
.....
at com.example.demo.DemoApplication.run(DemoApplication.kt:36) ~[main/:na]

[christophstrobl]

Thanks for the sample. There's been an update on constructor argument handling in the recent M3 release that fixes parameter conversion. However the sample reveals another issue in expression evaluation (#3842) that needs to be targeted before RC1.

[ntf]

You are welcome and glad this helps.

[christophstrobl]

I think we can close this one because #3842 has been resolved meanwhile. If you're still having trouble please feel free to drop a note and reopen the issue.

[ntf]

Thanks @christophstrobl , although I don't understand how the change set in #3842 fixed this issue but I will take some time to upgrade and revert if it doesn't fix the issue.