mongodb Aggregates Accumulators使用初步

import com.mongodb.BasicDBObject;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.model.Accumulators;
import com.mongodb.client.model.Aggregates;
import com.mongodb.client.model.Filters;
import org.bson.Document;
import org.bson.conversions.Bson;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.web.WebAppConfiguration;

import java.util.Arrays;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({"classpath:spring-context.xml"})
@WebAppConfiguration
public class MongoAggTest {

    /**
     * count
     * */
    @Test
    public void count(){
        Bson match = Aggregates.match(Filters.gte("age", 30));
        Bson group = Aggregates.group("$province", Accumulators.sum("cnt", 1));
        Bson sort = Aggregates.sort(new BasicDBObject("cnt", -1));
        MongoCollection<Document> coll = null;//get your coll
        MongoCursor<Document> iterator = coll.aggregate(Arrays.asList(match, group,sort)).iterator();
        while (iterator.hasNext()){
            Document next = iterator.next();
            System.out.println(next.toJson());
        }
    }

    /**
     * sum
     * */
    @Test
    public void sum(){
        Bson match = Aggregates.match(Filters.gte("age", 30));
        Bson group = Aggregates.group("$province", Accumulators.sum("cnt", "$age"));
        Bson sort = Aggregates.sort(new BasicDBObject("cnt", -1));

       MongoCollection<Document> coll = null;//get your coll

        MongoCursor<Document> iterator = coll.aggregate(Arrays.asList(match, group,sort)).iterator();
        while (iterator.hasNext()){
            Document next = iterator.next();
            System.out.println(next.toJson());
        }
    }

    /**
     * first聚合
     * */
    @Test
    public void first(){
        Bson match = Aggregates.match(Filters.gte("age", 30));
        Bson group = Aggregates.group("$province", Accumulators.first("first", "$$ROOT"));
        Bson sort = Aggregates.sort(new BasicDBObject("cnt", -1));
        MongoCollection<Document> coll = null;//get your coll
        MongoCursor<Document> iterator = coll.aggregate(Arrays.asList(match, group,sort)).iterator();
        while (iterator.hasNext()){
            Document next = iterator.next();
            System.out.println(next.toJson());
        }
    }

    /**
     * 多字段聚合
     * */
    @Test
    public void group()throws Exception{
        Bson group = Aggregates.group(new BasicDBObject("age", "$age").append("province", "$province"),
                Accumulators.sum("cnt", 1));
        MongoCollection<Document> coll = null;// do yourself
        MongoCursor<Document> iterator = coll.aggregate(Arrays.asList(group)).iterator();
        while (iterator.hasNext()){
            Document next = iterator.next();
            System.out.println(next.toJson());
        }
    }

    @Test
    public void add2Set()throws Exception{
        Bson group = Aggregates.group("$province", Accumulators.addToSet("nameSet", "$name"));
        MongoCollection<Document> coll = null;  //do yourself
        MongoCursor<Document> iterator = coll.aggregate(Arrays.asList(group)).iterator();
        while (iterator.hasNext()){
            Document next = iterator.next();
            System.out.println(next.toJson());
        }
    }
}