Java中的MongoDB查询，在嵌套对象中搜索/查找

Question

I'm having a little trouble with a query in Java on a MongoDB.

I have the follow structure in the database:

            {
              "_id" : ObjectId("5059c214707747cbc5819f6f"),
              "id" : "7",
              "title" : "test4",
              "keywords" : "keyword 1, keyword 2",

              "partner" : {
                "id" : "1",
                "name" : "partner",
                "keywords" : "partner keyword 1, partner keyword 2"
              },
              "status" : {
                "id" : "0",
                "name" : "Expired"
              },

              "modified" : "2012-09-27"
            }

I want the query the database for the field 'Status.name', example SELECT * FROM table WHERE status.name = 'Expired'

How would I do such a query in Java for MongoDB?

Thanks for any help or suggestions!

Answer 1

Here is an example:

import com.mongodb.Mongo;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBCursor;
import com.mongodb.DB;

public class MongoTest {

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

        // connect to the local database server
        Mongo m = new Mongo();

        DB db = m.getDB( "test" );

        DBCollection coll = db.getCollection("test");

        // delete all the data from the 'test' collection
        coll.drop();

        // make a document
        BasicDBObject doc = new BasicDBObject();

        doc.put("id", 7);
        doc.put("title", "test4");
        doc.put("modified", "2012-09-27");

        BasicDBObject status = new BasicDBObject();

        status.put("id", "1");
        status.put("name", "Expired");

        doc.put("status", status);

        // insert
        coll.insert(doc);

        BasicDBObject query = new BasicDBObject("status.name", "Expired");

        //  run the query and print the results out
        DBCursor cursor = coll.find(query);

        try {
            while (cursor.hasNext()) {
                System.out.println(cursor.next());
            }
        } finally {
            cursor.close();
        }

        m.close();
    }
}

Answer 2

MongoDB uses a 'match object' as a query. So to find objects that have status.name equal to "Expired", you could feed an object like such:

{ "status.name": "Expired" }

From Java you'll need to create a DBOjbect like the above to use as the match (returning everything that ... matches with the match object) and send that to the database as a query. Assuming you'll have a connection to MongoDB from Java, use the find -method to execute the query you're after.

Answer 3

BasicDBObject query = new BasicDBObject();

List<BasicDBObject> ob = new ArrayList<BasicDBObject>();

ob.add(new BasicDBObject("status.name", "Expired"));

List<BasicDBObject> foundDocument =   table.find(query)into(new ArrayList<BasicDBObject>());

for (int i = 0; i < foundDocument.size(); i++) {

System.out.println(foundDocument.get(i));
}

This will print all the rows having status as "Expired"

Answer 4

With MongoDB Java Driver v3.2.2 you can do something like this:

FindIterable<Document> iterable = collection.find(Document.parse("{\"status.name\": \"Expired\"}"));

This returns all documents containing "Expired" in the status.name nested field.