How to read array from mongoDB document in java?

Question

When I try to put this type1 array from mongoDB document , I can take that as an array through java by doing code like :

BasicDBList listEditionsAssets = (BasicDBList) nextAssets.get("areas");

following is type1 array :

{
 "ClientId" : "212",
 "UserId" :"212",
 "areas" : [
   {
     "Area 1" : "Chicago"
     "Area 2" : "LA",
     "Area 3" : "Boston" 
  ]
}

But,following is the data I have in mongoDB document :

following is 'type2' array :

{
 "ClientId" : "212",
 "UserId" :"212",
 "areas" : ["Chicago","LA","Boston" ]
}

When I try to retrieve "areas" array in java by using BasicDBList, it comes as "null". Because java is taking it as String. When I take it as

BasicDBObject result = (BasicDBObject) it.next();
String areas = (String) result.get("areas");

I can read is as String.

So how can I read "areas" in type2 document as an Array in java and not the String ?

Are you sure type2.areas is an array? I've tested on my local with mongo-java-driver 3.4.2. It does return a list with (List) dbObject.get("areas") — bvrakvs
– bvrakvs, Commented Mar 23, 2017 at 12:13
My object -> { "areas" : ["1", "2"] } and the result of above get with list casting -> ["1", "2"] — bvrakvs
– bvrakvs, Commented Mar 23, 2017 at 12:25
Hi, I am getting List as "null". I tried to take it as String and it shows the result.. BasicDBObject result = (BasicDBObject) it.next(); String areas = (result.getString("areas")); System.out.println(areas); Can't guess why getting the List null...can you please suggest have any idea? — Deva
– Deva, Commented Mar 24, 2017 at 11:02

An4o · Accepted Answer · 2021-07-16 18:48:44Z

1

The only significant difference between reading an array and reading a document is that, since the elements of an array do not have names, there is no field name to read, only a series of values:

reader.readStartArray();

while (reader.readBsonType() != BsonType.END_OF_DOCUMENT) {
    switch (reader.getCurrentBsonType()) {
        case INT32:
            int intValue = reader.readInt32();
            break;
        case INT64:
            long longValue = reader.readInt64();
            break;
        // ... handle each supported field type
    }
}

reader.readEndArray();

answered Jul 16, 2021 at 18:48

An4o

111 bronze badge

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

Collectives™ on Stack Overflow

How to read array from mongoDB document in java?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related