CODEWITHSUNDEEP
javaspringmongodbspring-dataspring-data-mongodb
user123
user123

Reputation: 577

How to project array element field in Spring Data Mongo DB Aggregation

How to project embedded array element field in Spring Data MongoDB Aggregation with the document sample below, I tried:

but didn't work.

Result document without projection:

{
    "id": "group1",
    "name": "Default Identity Management",
    "warningThreshold": 900000,
    "tariffId": "TR_0001",
    "active": false,
    "customers": [
        {
            "id": "1",
            "name": "David",
            "properties": [
                {
                    "name": "phone",
                    "value": "678"
                }
            ],
            "roles": [
                "dev"
            ]
        },
        {
            "id": "2",
            "name": "Peter",
            "properties": [
                {
                    "name": "phone",
                    "value": "770"
                }
            ],
            "roles": [
                "techsales",
                "dev"
            ]
        }
    ]
}

Expected document like this:

{
    "id" : "group1",
    "name" : "Group1",
    "tariffId" : "TR_0001",
    "warningThreshold" : 900000,
    "customers" : [
        {
            "id" : "1",
            "name" : "David",
            "properties" : [
                {
                    "name" : "phone",
                    "value" : "678"
                }
            ]
        },
        {
            "id" : "2",
            "name" : "Peter",
            "properties" : [
                {
                    "name" : "phone",
                    "value" : "770"
                }
            ]
        }
    ]
}

I would like to include customers[].id, customers[].name, customers[].properties.

Upvotes: 1

Views: 2753

Answers (1)

The Student Soul
The Student Soul

Reputation: 2492

I'd been trying to figure this out for a while now, but couldn't. And the other posts here on stackoverflow, and other places on the internet, didn't provide the solution I was looking for.

My problem was similar to the original author's: There's a document, which has a field which is an array of documents. I wanted to query all the top level fields in the document, and exclude a single field from the documents within the array.

s7vr's answer in the comments for the question did the job for me! Just re-posting that here since most people don't go through all the comments, and it is a really useful answer, that saved me from writing a lot of crappy code! :D

AggregationOperation project = new AggregationOperation() {
    @Override
    public Document toDocument(AggregationOperationContext aggregationOperationContext) {
        return new Document("$project", new Document("arrayField.nestedFieldToExclude", 0));
    }
};

With Lambda:

AggregationOperation project = aggregationOperationContext -> new Document("$project", new Document("arrayField.nestedFieldToExclude", 0));

Overall pipeline:

Aggregation aggregation = Aggregation.newAggregation(
    Aggregation.match(criteria),
    Aggregation.sort(Sort.Direction.DESC, "createdOn"),
    project);

I just wish there was a cleaner way to do this with the Spring MongoDB Data API directly, rather than using it this way with lambda functions.

Also, please note that the method AggregationOperation.toDocument(AggregationOperationContext aggregationOperationContext) has been deprecated as of spring-data-mongodb version 2.2.

Upvotes: 2

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