MongoClient Bring back individual items in an array if they match using Java

I have a document...

doc =  
    { 
        "Loan_Num"       : "Loan002",
        "Info" : "Loan for processing details."
        "Loan_Items" :   [
                            {
                                "Invoice_Num"  : "32134324",
                                "Quantity"  : 1,
                                "Amount_Required" : "£4"
                            },

                            {
                                "Book_Barcode"  : "22222",
                                "Quantity"  : 1,
                                "Amount_Required" : "£2"
                                "Amount_Payed" : true
                            }
                        ]
    };

I'm trying to create a query to bring back any results that have the "Amount_Required" key but don't have the "Amount_Payed" key.

So from the above document I would expect this result...

    { 
        "Loan_Num"       : "Loan002",
        "Info" : "Loan for processing details."
        "Loan_Items" :   [
                            {
                                "Invoice_Num"  : "32134324",
                                "Quantity"  : 1,
                                "Amount_Required" : "£4"
                            }
                        ]
    };

This is my Java code...

 BasicDBObject searchQuery = new BasicDBObject();
    searchQuery.append("Loan_Num", "Loan002");
    searchQuery.append("Loan_Items.Fine_Amount", new BasicDBObject("$exists", true));
    searchQuery.append("Loan_Items.Fine_Payed", new BasicDBObject("$exists", false));

Problem being is it doesn't return anything since the "Amount_Played" exists in the second element in the array. How could I achieve this result ? - Many Thanks

You could try using $elemMatch:

Your query would look something like this:

db.collection.find({"Loan_Items" : {$elemMatch : { "Amount_Required" : { $exists : true}, "Amount_Payed" : { $exists : false}}}})

Hope this helps!