How to update field type in a document using Java MongoDB Reactive driver?

Question

I have a document in MongoDB collection:

  {
    "fOne": "strValue",
    "fTwo": {
      "nestedFArray": [
        {
          "dateF": "2010-01-02T13:00:01"
        },
        {
          "dateF": "2010-01-02T13:00:01"
        }
      ],
      "nestedFObject": {
        "anotherDateF": "2010-01-02T13:00:01"
      }
    }
  }

fields fTwo.nestedFArray[0].dateF, fTwo.nestedFArray[1].dateF, fTwo.nestedFObject.anotherDateF stored as a string type; How to replace types of this field with DateTime type when I have a json paths for fields using java mongo reactive driver?

$.fTwo.nestedFArray[0].dateF

$.fTwo.nestedFArray[1].dateF

$.fTwo.nestedFObject.anotherDateF

score 1 · Answer 1 · answered Dec 31 '19 at 17:32

The query is an aggregation which converts the string date values to Date values. The result list from the aggregation is iterated and the modified documents are updated in a for-loop. Note the code assumes a collection with multiple input documents.

The Java Code:

import org.bson.Document;
import org.bson.conversions.Bson;
import org.bson.types.ObjectId;
import com.mongodb.reactivestreams.client.MongoClient;
import com.mongodb.reactivestreams.client.MongoClients;
import com.mongodb.reactivestreams.client.MongoCollection;
import com.mongodb.reactivestreams.client.MongoDatabase;
import com.mongodb.client.model.UpdateOneModel;
import com.mongodb.client.model.WriteModel;
import com.mongodb.bulk.BulkWriteResult;
import java.util.*;

public class MongoReact {

    public static void main(String[] args) 
            throws Throwable {

        MongoClient mongoClient = MongoClients.create();
        MongoDatabase db = mongoClient.getDatabase("testdb");
        MongoCollection<Document> collection = db.getCollection("test");

        List<Bson> pipeline =    
            Arrays.asList(
                new Document("$project", 
                    new Document("fTwo.nestedFObject.anotherDateF", 
                        new Document("$dateFromString", 
                            new Document("dateString", "$fTwo.nestedFObject.anotherDateF")
                        )
                    )
                    .append("fTwo.nestedFArray",
                        new Document("$map", 
                            new Document("input", "$fTwo.nestedFArray") 
                                .append("as", "e")
                                .append("in",
                                    new Document("dateF",
                                        new Document("$dateFromString", 
                                            new Document("dateString", "$$e.dateF")
                                        )
                                    )
                                )
                            )
                        )
                )
            );

        SubscriberHelpers.ObservableSubscriber<Document> querySubscriber =
            new SubscriberHelpers.ObservableSubscriber<Document>();
        collection.aggregate(pipeline).subscribe(querySubscriber);
        querySubscriber.await();
        List<Document> resultDocs = querySubscriber.getReceived();

        List<WriteModel<Document>> updates = new ArrayList<>();

        for (Document doc : resultDocs) {
            ObjectId id = (ObjectId) doc.get("_id");
            Document f2Doc = (Document) doc.get("fTwo");
            updates.add(new UpdateOneModel<Document>(
                                new Document("_id", id), 
                                new Document("$set", new Document("fTwo", f2Doc))
            ));
        }

        SubscriberHelpers.PrintSubscriber<BulkWriteResult> updateSubscriber = 
            new SubscriberHelpers.PrintSubscriber<BulkWriteResult>("Bulk write results: %s");
        collection.bulkWrite(updates).subscribe(updateSubscriber);
        updateSubscriber.await();

        mongoClient.close();
    }
}

NOTES:

The SubscriberHelpers is a utility class used in the above code. I have used it as shown in the Quick Tour (with examples) section of the Reactive Streams Java Driver page.

The source code for the SubscriberHelpers.java can be found at: mongo-java-driver-reactivestreams/examples/tour/src/main/tour/. The usage of the code and examples source code is also there - you can compile and use it.

I have used MongoDB server 4.0, Java SE 8, MongoDB Reactive Streams driver 1.10.0 and mongodb-driver-async 3.9.0 to work with the above code.

How to update field type in a document using Java MongoDB Reactive driver?

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