MongoDB aggregation condition translated to JAVA driver

Question

I'm relatively new to MongoDB and I'm currently working with java towards a "find by most tags matching" solution to information within a collection.

I'm stuck now trying to translate a MongoDB shell operation to the JAVA driver version (this sintaxis is part of the definitions needed )

$cond:[{$eq: ["$tags", 200]}, 1, 0]

What would be a correct JAVA implementation for the sentence above?

Thank you in advance

Miguel Cartagena · Accepted Answer · 2012-12-16 18:35:54Z

2

Whatever the $cond object where in your aggregation operation, to build it to should do something like this:

BasicDBList eqList = new BasicDBList();
eqList.add("$tags");
eqList.add(200);

DBObject eqObject = BasicDBObjectBuilder.start()
    .add("$eq", eqList)
    .get();

BasicDBList condList = new BasicDBList();
condList.add(eqObject);
condList.add(1);
condList.add(0);

DBObject condObject = BasicDBObjectBuilder.start()
    .add("$cond", condList)
    .get();

I'm confusing about your aggregation operation, could you give more details?

answered Dec 16, 2012 at 18:35

Miguel Cartagena

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1 Comment

jmikola Over a year ago

It looks like the OP just needed help creating the DBObject, but to answer your question, $cond is one of the aggregation framework expressions (like a SQL IF() function).

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