Execute mongoDB shell like query using a java class

Question

Using a java class i want to execute MongoDB shell query stored in a String variable.Currently i am using the following code.

String query="db.INSTANT.insert( { item: 'card', qty: 12 } )";
MongoClient mongo = new MongoClient("localhost",27017);
DB db = mongo.getDB("mydb");
db.eval(query);

The above code works fine for insert. But i want to execute find statement like query=db.INSTANT.find({"item":"card"}).Is there any way to execute this query and print the collection set.

Marco · Accepted Answer · 2018-12-21 08:51:39Z

1

Assuming that the function of eval has been deprecated since version 3.0.

The helper db.eval() in the Java Driver wraps the mongo eval command, So you can evaluate JavaScript code this way

String query="db.INSTANT.find( { item: 'card', qty: 12 } ).toArray()";

answered Dec 21, 2018 at 8:51

Marco

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5 Comments

Nandu Over a year ago

I want to print the result set. Can you please demonstrate it with a sample code.

Marco Over a year ago

You can cast result as (List<BasicDBObject>) db.eval(query);

Nandu Over a year ago

I typecasted like "List<BasicDBObject> ob =(List<BasicDBObject>) db.eval(query);" and I am getting this exception. "Exception in thread "main" java.lang.ClassCastException: com.mongodb.BasicDBObject cannot be cast to java.util.List at com.sixdee.demo.MongoQuery.main(MongoQuery.java:23)". What goes wrong in it.

Marco Over a year ago

Did you add the "toArray()"?

Nandu Over a year ago

Thank you.It is working. Is there any another way to do this. My intention is to execute normal MongoDB query using a java class.

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