How to do MongoDB query with JavaScript expression in Java code , like in Mongo shell

Question

1. I know how to query with JavaScript expression in Mongo shell ( collection name is resource_phys. field name is val which defined as String type and contains only numeric value ) :

//in Mongo shell:
var query1 = ("Number(this.val)>-1 && Number(this.val)<3")
db.resource_phys.find(query1)
//result found

2. Now, I want to do the same thing in Java code but cannot find any API to support JavaScript. I solicit your help to give some hints.

3.P.s. If the field val is numeric type, I am aware of using operator $gt and $lt :

//in Java codes:
DBCollection coll = db.getCollection("resource_phys");
DBObject query2 = new BasicDBObject("val",new BasicDBObject("$gt",-1).append("lt",3));
DBCursor cursor = coll.find(query2);
//result got in cursor

Neil Lunn · Accepted Answer · 2014-04-29 03:43:06Z

1

The form of query you are doing in the shell is actually just a shortcut form of the $where operator. So you would translate like this:

    DBObject query = new BasicDBObject(
            "$where",
            "Number(this.val)>-1 && Number(this.val)<3"
    );

Please note the documentation though, as running JavaScript is not a good idea for performance. You really should convert your strings to be actual numeric values.

answered Apr 29, 2014 at 3:43

Neil Lunn

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1 Comment

user3583514 Over a year ago

Amazing! Awesome!Fabulous!Thanks! ---I did tried using $where but not worked, but now your code works fine.so strange! And I did know the performance issue but just leave it right now...Thanks again!

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