Retrieving a single field from MongoDB using Selenium/Java - mongodb

Question

I'm just switching from MySQL to MongoDB and it's a little confusing. We have our database stored in MongoDB and using Java-Selenium in the front end. I am trying to retrieve just one single data from the database. The code below retrieves all the data present in the database:
DBCursor cursor = dbCollection.find();
while(cursor.hasNext())
{
int i=1;
System.out.println(cursor.next());
i++;
}
This is my database lets say:
{
"name" : "Su_123",
"email" : "test#gmail.com",
"_id" : ObjectId("12345656565656")
}
I want to retrieve just the email field (test#gmail.com) from the document where _id = ObjectId("12345656565656") and store this in a String field.
How do I go about coding this? find() retrieves the entire row.

Answer 1

For newer drivers, since 3.7.1
To get specific document that matches a filter:
Document doc = collection.find(eq("email", "test#gmail.com")).first();
It can be used to find the first document where the field email has the value test#gmail.com. And pass an eq filter object to specify the equality condition.
By the same logic using id:
Document document = myCollection.find(eq("_id", new ObjectId("12345656565656"))).first();
To get specific value of the field from selected document:
String value = (String) doc.get("email");
For older drivers like 2.14.2 and 2.13.3
To get a single document with a query:
BasicDBObject query = new BasicDBObject("email", "test#gmail.com");
cursor = coll.find(query);
try {
while(cursor.hasNext()) {
//System.out.println(cursor.next());
}
} finally {
cursor.close();
}
To see more details for newer Mongodb Java driver.
To see more details for older Mongodb Java driver.
To see more details from Mongodb Official Docs.