Question

我有一个mongo聚合组查询：

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

我需要在Java Spring-Data-MongoDB中使用此查询，我目前的解决方案如下所示：

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

问题是我不知道如何为推送方法（版本，作者，dateAdded）添加更多字段。是否可以使用Spring-Data-MongoDB？

Answer 1

您可以直接将BasicDbObject传递给任何聚合管道阶段。

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

Answer 2

注意：MongoDBversión2.6 - 3.0（兼容的Java驱动程序）

我已经扩展org.springframework.data.mongodb.core.aggregation.AggregationOperation类来实现自定义toDBObject方法：

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);
    }

}

在你的情况下，它将是：

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();

希望这会对你有所帮助。

Answer 3

在新版本的spring-data-mongodb：2.x.x中，AggregationOperation需要返回Document而不是DBObject，因此更新后的类将是：

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);
    }
}

另外，为了更易于使用，我将添加实用程序接口（java 8+，对于Java 7或更低版本，您可以将其转换为类utils）：

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);
    }

}

然后我们可以将接口静态导入到我们的类中：

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

并将其与其他Spring数据AggregationOperation一起在聚合管道中使用，如下所示：

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

MongoDB $ aggregate $ push Java Spring Data中的多个字段

3 个答案: