In MongoDB Java Driver how do you use $filter

Question

I have a query that works in MQL. I need to translate it into Java. The query in MQL looks like this

db.<collection>.aggregate( [
            {
                $project: {
                    "MonitoringLocationIdentifier": 1,
                    epochTimes: {
                        $filter: {
                            input: "$epochTimes",
                            as: "epochTime",
                            cond: { $and: [ {$gte: [ "$$epochTime", NumberLong("0") ]}, {$lte: ["$$epochTime", NumberLong("558268020000")]} ]}
                        }
                    },
                }
            }
        ] )

The collection contains documents that look like this

{"_id" : ObjectId("633218dfec534a6fe90106b8"), 
 "MonitoringLocationIdentifier": "Site1", 
 "epochTimes" : [ NumberLong("451058760000"), NumberLong("558189720000"), NumberLong("516460860000") ] }

I am trying to get all the documents in the collection but filter the "epochTimes" for every document by a min/max.

Any Java Driver wizards out there?

Answer 1

I searched for mongodb java aggregation and Google yielded this "Java - Aggregation Pipeline" article from them. It walks through some examples, but also mentions that the Compass tool has an Export Pipeline to Specific Language functionality.

So after opening Compass I used CREATE NEW -> Pipeline from text and pasted in your MQL from above. After it was loaded I clicked EXPORT TO LANGUAGE , chose JAVA in the drop down, added Include Import Statements and it produced the following:

import java.util.Arrays;
import org.bson.Document;

Arrays.asList(new Document("$project", 
    new Document("MonitoringLocationIdentifier", 1L)
            .append("epochTimes", 
    new Document("$filter", 
    new Document("input", "$epochTimes")
                    .append("as", "epochTime")
                    .append("cond", 
    new Document("$and", Arrays.asList(new Document("$gte", Arrays.asList("$$epochTime", 0L)), 
                            new Document("$lte", Arrays.asList("$$epochTime", 558268020000L)))))))))

(There is also a Include Driver Syntax button that seems to be even more verbose if needed).

So I'm no Java Driver wizard, but hope this helps anyway!