Spring Data MongoDB Aggregation using project and $map - spring

Question

I want to know the SpringData equivalent code for the following native mongoDB query.
{
$project: {
_id: "$_id",
login: "$login",
firstName: "$firstName",
lastName: "$lastName",
email: "$email",
deactivateFlag: "$deactivateFlag",
createdOn: "$createdOn",
createdBy: {
"$map": {
"input": "$created_by",
"as": "u",
"in": {
"name": {
"$concat": ["$$u.firstName", " ", "$$u.lastName"]
},
}
}
}
}
}

Answer 1

This is an old question but if anyone else finds it on a Google search this is how to solve it. In fact you can do this for any complex mongodb query that Spring JPA can't handle out of the box.
You need to write a custom Document to inject into the projection. The example is in Kotlin but you'll get the idea for Java. I've not tested it properly but should get you what you want.
val mapExpression = BasicDBObject()
mapExpression["input"] = "\$created_by"
mapExpression["as"] = "u"
val concat = BasicDBObject("\$concat", listOf("\$\$u.firstName", " ", "\$\$u.lastName"))
mapExpression["in"] = BasicDBObject("name", concat)
val createdByFilter = Document("\$map", mapExpression)
project("_id", "login", "firstName", "lastName", "email", "deactivateFlag", "createdOn").and(createdByFilter).`as`("createdBy")