Stuck on an issue?

Lightrun Answers was designed to reduce the constant googling that comes with debugging 3rd party libraries. It collects links to all the places you might be looking at while hunting down a tough bug.

And, if you’re still stuck at the end, we’re happy to hop on a call to see how we can help out.

Support for $ projection

See original GitHub issue

Hello, first of all thanks for the great work 😃

We are using a custom query in our project with projection, but it seems that mongo-java-server does not support such kind of projection. The query looks for objects which have a specific nested object in an array and the query returns the object with only the matching nested object in the array. It looks like this:

@Query(value = "{ 'states': { $elemMatch: { 'state': { $eq: \"INSTALLED\" }, 'internalID': { $eq: ?0 } } } }", fields = "{ 'states.$': 1, 'serialnumber': 1 }") List<MyObject> findWithCustomQuery(String internalID);

So if we have a object like this:

object1:
|---serialnumber: 1234
|---states:
     |---[0]
           |---state: INSTALLED
           |---internalID: abc123
     |---[1]
           |---state: UPDATE
           |---internalID: abc456
object2:
|---serialnumber: 5678
|---states:
     |---[0]
           |---state: UPDATE
           |---internalID: abc123
     |---[1]
           |---state: UPDATE
           |---internalID: abc456

and the query is done with internalID abc123 only the first object containing an array with the matching object should be returned. This works in mongo 3.6, but not with mongo-java-server. If I use mongo-java-server all fields of the array are set to null and all objects in the array are returned. So the expected result would be:

object1:
|---serialnumber: 1234
|---states:
     |---[0]
           |---state: INSTALLED
           |---internalID: abc123

But we actually get:

object1:
|---serialnumber: 1234
|---states:
     |---[0]
           |---state: null
           |---internalID: null
     |---[1]
           |---state: null
           |---internalID: null

Any help is appreciated!