Mongo query to filter inner Arraylist items in Spring Boot using Mongo Template

Question

Below is my DOCUMENT:

@Document(collection = "products")
@Data
@EqualsAndHashCode
public class Product {

    @Id
    private String id;

    @Field("lang_content_list")
    private List<ProductLangContent> contentList;

    @Data
    public static class ProductLangContent {
        @Field("lang")
        private String lang;
    }

}

I want to get only those contentList where lang = 'en'. lang is unique within innner list.

Note: I am using Mongotemplate

My sample json is:

{
    "_id" : ObjectId("5d2040f9f7c5ac1e9d8ef712"),
    "lang_content_list" : [ 
        {
            "lang" : "en"
        }, 
        {
            "lang" : "np"
        }
    ]
    "_class" : "com.sn.application.model.Product"
}

Desired query result is:

{
    "_id" : ObjectId("5d2040f9f7c5ac1e9d8ef712"),
    "lang_content_list" : [ 
        {
            "lang" : "en"
        }
    ]
}

I tried couple of queries but got no luck:

Aggregation aggregation = newAggregation(
                   project().and(filter("contentList")
                     .as("item")
                     .by(valueOf(
                          "item.lang")
                           .equalToValue(
                          "en")))
                  .as("contentList")
        );
        List<Product> results = mongoTemplate.aggregate(aggregation, Product.class, Product.class).getMappedResults();

output is: contentList is null.

Tried:

Criteria elementMatchCriteria = Criteria.where("contentList").elemMatch(Criteria.where("lang").is("en"));

It gives all elements in contentList. I don't want that. I want only one object in inner list where lan = 'en' .

Huge Thank you in advance.

Tried:

AggregationOperation match = Aggregation.match(Criteria.where("contentList.lang").is("en"));
        AggregationOperation unwind = Aggregation.unwind("contentList");
        AggregationOperation group = Aggregation.group("id")            
                .push("contentList").as("contentList");

        List<AggregationOperation> operations = new ArrayList<>();
        operations.add(match);
        operations.add(unwind);
        operations.add(match);
        operations.add(group);
        Aggregation aggregation = Aggregation.newAggregation(operations);
        List<Product> results = mongoTemplate.aggregate(aggregation, Product.class, Product.class).getMappedResults();
        System.out.println(results.get(0).getContentList() != null);

output is: false. Inner array object is coming as null.

Rajat Goel · Accepted Answer · 2019-07-08 07:14:04Z

3

Your document has an array field "contentList" which will be having multiple "lang". I'm assuming you want to filter/get all those documents in which atleast one "lang" in "contentList" is "en". Then use :

Criteria elementMatchCriteria = Criteria.where("contentList.lang").is("en"));

If you want only that object in the inner array where lang='en', you need to use aggregation pipeline like:

Link: https://mongoplayground.net/p/JaJ7420i4qJ

db.collection.aggregate([
  {
    $match: {
      "lang_content_list.lang": "en"
    }
  },
  {
    $unwind: "$lang_content_list"
  },
  {
    $match: {
      "lang_content_list.lang": "en"
    }
  },
  {
    $group: {
      "_id": "$_id",
      "_class": {
        $first: "$_class"
      },
      "lang_content_list": {
        $push: "$lang_content_list"
      }
    }
  }
])

The reason for using the last group stage is that in your object, contentList is an array so we need to wrap lang object as array, otherwise not needed if you can change return type object.

In Spring MongoTemplate code:

AggregationOperation match = Aggregation.match(Criteria.where("lang_content_list.lang").is("en"));
AggregationOperation unwind = Aggregation.unwind("lang_content_list");
AggregationOperation group = Aggregation.group("_id")             
        .first("_class").as("_class")                
        .push("lang_content_list").as("lang_content_list");

List<AggregationOperation> operations = new ArrayList<>();
operations.add(match);
operations.add(unwind);
operations.add(match);
operations.add(group);
Aggregation aggregation = Aggregation.newAggregation(operations);
List<Product> results = mongoTemplate.aggregate(aggregation, Product.class, Product.class).getMappedResults();

edited Jul 8, 2019 at 7:14

answered Jul 7, 2019 at 17:14

Rajat Goel

2,3051 gold badge20 silver badges37 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Nabin Kumar Khatiwada Over a year ago

Thank you. But i want only that object in the inner array where lang='en'. Is there a way to filter it out? I have updated question for better understanding.

Rajat Goel Over a year ago

updated answer for only that object in the inner array where lang='en'

Nabin Kumar Khatiwada Over a year ago

Sorry for interruption, can you update query for syntax MongoTemplate package i'm using is: org.springframework.data.mongodb.core.MongoTemplate;

Nabin Kumar Khatiwada Over a year ago

Hey thanks a lot. I found a solution after trying for sometime from your suggestion. Thanks alot.

Nabin Kumar Khatiwada Over a year ago

Hi, @Rajat Goel ,can you help me out once again. I have question posted in following link: stackoverflow.com/questions/57132939/…

Collectives™ on Stack Overflow

Mongo query to filter inner Arraylist items in Spring Boot using Mongo Template

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related