MongoDB $aggregate $push multiple fields in Java S

问题:

I have a mongo aggregate group query:

db.wizard.aggregate(
{
$group: {
    _id: "$title",
    versions: { $push: {version:"$version", author:"$author", dateAdded:"$dateAdded"}}
    }
})

I need this query in Java Spring-Data-MongoDB, my current solution looks like this:

    Aggregation agg = Aggregation.newAggregation(
            Aggregation.group("title").
                    push("version").as("versions")
    );

Problem is that i don't know how to add more fields to push method (version, author, dateAdded). Is it possible with Spring-Data-MongoDB?

回答1:

You can directly pass the BasicDbObject to any of the aggregation pipeline stage.

Aggregation agg = newAggregation(
            group("title").
            push(new BasicDBObject
                   ("version", "$version").append
                   ("author", "$author").append
                   ("dateAdded", "$dateAdded")).as("versions"));

回答2:

Note: MongoDB versión 2.6 - 3.0 (compatible Java driver)

I've extended org.springframework.data.mongodb.core.aggregation.AggregationOperation class to implement custom toDBObject method:

public class GenericAggregationOperation implements AggregationOperation {

    private String operator;
    private DBObject query;

    /**
     * Default constructor.
     * 
     * @param operator MongoDB operator ($group, $sort, $project, etc..)
     * @param query MongoDB aggregation query step string
     */
    public GenericAggregationOperation(String operator, String query) {
        this(operator, (DBObject) JSON.parse(query));
    }

    /**
     * Default constructor.
     * 
     * @param operator MongoDB operator ($group, $sort, $project, etc..)
     * @param query MongoDB aggregation query step DBObject
     */
    public GenericAggregationOperation(String operator, DBObject query) {
        this.operator = operator;
        this.query    = query;
    }

    @Override
    public DBObject toDBObject(AggregationOperationContext context) {

        return new BasicDBObject(operator, query);
    }

}

In your case, it would be:

List<AggregationOperation> list = new ArrayList<AggregationOperation>();
lista.add(new GenericAggregationOperation("$group", "{ \"_id\": \"$title\", \"versions\": { \"$push\": { \"version\":\"$version\", \"author\":\"$author\", \"dateAdded\":\"$dateAdded\"}} }"));

TypedAggregation<EpisodeIndexDto> agg = Aggregation.newAggregation(
    YourClassTitleVersion.class, list);
mongoOperations.aggregate(agg, YourClassTitleVersion.class,
    YourClassTitleVersion.class).getMappedResults();

Hope this helps you.

回答3:

In the new version spring-data-mongodb:2.x.x the AggregationOperation need to return Document instead of DBObject, so the updated class will be:

import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import org.bson.Document;
import org.springframework.data.mongodb.core.aggregation.AggregationOperation;
import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;

public class GenericAggregationOperation implements AggregationOperation {

    private String operator;
    private DBObject query;

    public GenericAggregationOperation(String operator, DBObject query) {
        this.operator = operator;
        this.query = query;
    }

    public GenericAggregationOperation(String operator, String query) {
        this(operator, BasicDBObject.parse(query));
    }

    @Override
    public Document toDocument(AggregationOperationContext context) {
        return new Document(operator, query);
    }
}

Plus to make it easier to be used I'll add utility interface (java 8+, for java 7 or lower you can convert this to class utils instead):

import com.mongodb.DBObject;
import org.springframework.data.mongodb.core.aggregation.AggregationOperation;

public interface GenericAggregationUtils {

    static AggregationOperation aggregate(String operation, String query) {
        return new GenericAggregationOperation(operation, query);
    }

    static AggregationOperation aggregate(String operation, DBObject query) {
        return new GenericAggregationOperation(operation, query);
    }

}

And then we can static import the interface into our class:

import static com.example.mongodb.aggregation.GenericAggregationUtils.*;

And use it in the aggregation pipeline together with other spring data AggregationOperation like this:

Aggregation aggregation = newAggregation(YourDocCollection.class,
    aggregate("$group", "{ \"_id\": \"$title\", \"versions\": { \"$push\": { \"version\":\"$version\", \"author\":\"$author\", \"dateAdded\":\"$dateAdded\"}} }"),
    sort(Sort.Direction.ASC, "title"),
    ...
);