How to use ConcatArrays in Spring Data MongoDB - spring

Question

I have the following JS code:
$concatArrays: [
"$some.path",
[
{
"foo": "baz",
"x": 5
}
]
]
How do I do the same with ArrayOperators.ConcatArrays?

Answer 1

Toy can use like following. You can pass the aggregation expresion or reference field name in concat(). So what you can do is, you can add the new array before concat() like
db.collection.aggregate([
{
$addFields: {
secondArray: [
{ "foo": "baz", "x": 5 }
]
}
},
{
"$project": {
combined: {
"$concatArrays": [ "$path", "$secondArray" ]
}
}
}
])
Working Mongo playground
ArrayOperators.ConcatArrays concatArrays = ArrayOperators.ConcatArrays
.arrayOf("path")
.concat("secondArray");

Answer 2

Assuming the array field is defined as follows in a document:
{
"_id": ObjectId("60bdc6b228acee4a5a6e1736"),
"some" : {
"path" : [
{
"foo" : "bar",
"x" : 99
}
]
},
}
The following Spring Data MongoDB code returns the result- an array with two elements. The array field "some.path" and the input array myArr are concatenated using the ArrayOperators.ConcatArrays API.
String json = "{ 'foo': 'baz', 'x': 5 }";
Document doc = Document.parse(json);
List<Document> myArr = Arrays.asList(doc);
MongoOperations mongoOps = new MongoTemplate(MongoClients.create(), "testDB");
Aggregation agg = newAggregation(
addFields()
.addFieldWithValue("myArr", myArr)
.build(),
addFields()
.addField("result").withValue(ConcatArrays.arrayOf("$some.path").concat("$myArr"))
.build()
);
AggregationResults<Document> results = mongoOps.aggregate(agg, "testColl", Document.class);