Example usage for org.springframework.data.mongodb.core.aggregation Aggregation limit

Introduction

In this page you can find the example usage for org.springframework.data.mongodb.core.aggregation Aggregation limit.

Prototype

public static LimitOperation limit(long maxElements) 

Source Link

Document

Creates a new LimitOperation limiting the result to the given number of elements.

Usage

From source file:org.ingini.mongodb.spring.example.aggregation.TestAggregationFramework.java

/**
 * Example taken from https://github.com/mongodb/mongo-ruby-driver/wiki/Aggregation-Framework-Examples
 * Command line import: mongoimport --drop --db aggregation_test_db --collection name_days name_days.json
 * <p>//from  w  w  w . j av a2s . com
 *      db.name_days.aggregate({$project : {names : 1, _id : 0}},
 *                             {$unwind : '$names'},
 *                             {$group : {_id: '$names', counter: {$sum: 1}}},
 *                             {$sort : {counter: -1}},
 *                             {$limit : 10});
 * </p>
 */
@Test
public void shouldFindThe10MostCommonNames() {
    //GIVEN
    CollectionManager.cleanAndFill(mongoTemplate.getDb(), "name_days.json", NameData.COLLECTION_NAME);
    int limit = 10;

    //WHEN
    AggregationResults<AggregatedNameData> aggregationResult = mongoTemplate.aggregate(
            Aggregation.newAggregation(NameData.class, Aggregation.project("names").andExclude("_id"),
                    Aggregation.unwind("names"), Aggregation.group("names").count().as("counter"),
                    Aggregation.sort(Sort.Direction.DESC, "counter"), Aggregation.limit(limit)),
            AggregatedNameData.class);

    //THEN
    assertThat(aggregationResult.getMappedResults()).hasSize(10);
    assertThat(aggregationResult.getMappedResults().get(0)).isEqualTo(new AggregatedNameData("Jana", 21));

}

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