How to query a array of json in a mongodb document using spring data mongodb

Question

I am using spring data mongodb sdk to query mongo db.

The document in mongoDb looks like this:

{
 "data": {
     "suggestions":[
         {
            "key": "take",
             "value": 1

         },
         {
            "key": "donttake",
             "value": 0

         }
      ]
  }  
}

In my api request I have a structure similar to "suggestions" element above. I want to create a query criteria where "is" clause should be the value of "suggestions" element in the api request.

I tried the following code using spring data mongo db:

JsonParser jsonParser = new JsonParser();
ObjectMapper objMapper = new ObjectMapper();
String jsonArrayString = objMapper.writeValueAsString(apirequest.getSuggestions());
JsonArray arrayFromString = jsonParser.parse(jsonArrayString).getAsJsonArray();

criteria = Criteria.where("data.suggestions").is(arrayFromString);

The problem with this code is that when I debug and see the query that gets created using criteria above, I goes in as $java: [{"key": "take", "value": 1}]

Therefore, it can't match it with the mongo document and doesn't fetch me any result.

Is there another way to query and array of documents in mongodb from spring data mongo ?

Hary · Accepted Answer · 2018-01-16 15:28:43Z

4

I followed a completely different approach by reading some information on querying arrays in mongodb available at

https://docs.mongodb.com/manual/tutorial/query-array-of-documents/

I used elemMatch to solve this problem as follows:

Let's say my API request gets mapped to and object suggestions and keyVal is an object that stores the keyVal pair.

for (KeyVal keyVal: suggestions()){

  Criteria c = 
         Criteria.where("key").is(keyVal.key()).and("value").is(keyVal.value());
  criteria = Criteria.where("data.suggestions").elemMatch(c); 
}

Then criteria can be used in a mongo Query

Also, keep in mind that elemMatch doesn't care about the ordering of elements inside a document in an array. So that way, elemMatch solves the purpose well.

answered Jan 16, 2018 at 15:28

Hary

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1 Comment

Tim Biegeleisen Over a year ago

For anyone looking for a simple example of how to search JSON objects within an array in some outer enclosing key, this Q&A hits the nail on the head +1.

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