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Java MongoDB: документ запроса

Java MongoDB: запрос документа

В этом руководстве мы покажем вам несколько распространенных способов получения или запроса документа из коллекции.

Тестовые данные

Вставьте 5 фиктивных документов для тестирования. 

{ "_id" : { "$oid" : "id"} , "number" : 1 , "name" : "example-1"}
{ "_id" : { "$oid" : "id"} , "number" : 2 , "name" : "example-2"}
{ "_id" : { "$oid" : "id"} , "number" : 3 , "name" : "example-3"}
{ "_id" : { "$oid" : "id"} , "number" : 4 , "name" : "example-4"}
{ "_id" : { "$oid" : "id"} , "number" : 5 , "name" : "example-5"}

1. Find () примеры

1.1 Get first matched document only.

    DBObject doc = collection.findOne();
    System.out.println(dbObject);

Выход 

    { "_id" : { "$oid" : "id"} , "number" : 1 , "name" : "example-1"}

1.2 Get all matched documents.

    DBCursor cursor = collection.find();
    while(cursor.hasNext()) {
        System.out.println(cursor.next());
    }

Выход 

{ "_id" : { "$oid" : "id"} , "number" : 1 , "name" : "example-1"}
{ "_id" : { "$oid" : "id"} , "number" : 2 , "name" : "example-2"}
{ "_id" : { "$oid" : "id"} , "number" : 3 , "name" : "example-3"}
{ "_id" : { "$oid" : "id"} , "number" : 4 , "name" : "example-4"}
{ "_id" : { "$oid" : "id"} , "number" : 5 , "name" : "example-5"}

1.3 Get single field from matched document.

    BasicDBObject allQuery = new BasicDBObject();
    BasicDBObject fields = new BasicDBObject();
    fields.put("name", 1);

    DBCursor cursor = collection.find(allQuery, fields);
    while (cursor.hasNext()) {
        System.out.println(cursor.next());
    }

Выход 

{ "_id" : { "$oid" : "id"} , "name" : "example-1"}
{ "_id" : { "$oid" : "id"} , "name" : "example-2"}
{ "_id" : { "$oid" : "id"} , "name" : "example-3"}
{ "_id" : { "$oid" : "id"} , "name" : "example-4"}
{ "_id" : { "$oid" : "id"} , "name" : "example-5"}

2. Найти () и Сравнение

2.1 Get all documents where number = 5.

    BasicDBObject whereQuery = new BasicDBObject();
    whereQuery.put("number", 5);
    DBCursor cursor = collection.find(whereQuery);
    while(cursor.hasNext()) {
        System.out.println(cursor.next());
    }

Выход 

{ "_id" : { "$oid" : "id"} , "number" : 5 , "name" : "example-5"}

2.2 $in example – Get documents where number in 2, 4 and 5.

    BasicDBObject inQuery = new BasicDBObject();
    List list = new ArrayList();
    list.add(2);
    list.add(4);
    list.add(5);
    inQuery.put("number", new BasicDBObject("$in", list));
    DBCursor cursor = collection.find(inQuery);
    while(cursor.hasNext()) {
        System.out.println(cursor.next());
    }

Выход 

{ "_id" : { "$oid" : "id"} , "number" : 2 , "name" : "example-2"}
{ "_id" : { "$oid" : "id"} , "number" : 4 , "name" : "example-4"}
{ "_id" : { "$oid" : "id"} , "number" : 5 , "name" : "example-5"}

2.3 $gt $lt example – Get documents where + 5 > number > 2 +.

    BasicDBObject gtQuery = new BasicDBObject();
    gtQuery.put("number", new BasicDBObject("$gt", 2).append("$lt", 5));
    DBCursor cursor = collection.find(gtQuery);
    while(cursor.hasNext()) {
        System.out.println(cursor.next());
    }

Выход 

{ "_id" : { "$oid" : "id"} , "number" : 3 , "name" : "example-3"}
{ "_id" : { "$oid" : "id"} , "number" : 4 , "name" : "example-4"}

2.4 $ne example – Get documents where + number != 4 +.

    BasicDBObject neQuery = new BasicDBObject();
    neQuery.put("number", new BasicDBObject("$ne", 4));
    DBCursor cursor = collection.find(neQuery);
    while(cursor.hasNext()) {
        System.out.println(cursor.next());
    }

Выход 

{ "_id" : { "$oid" : "id"} , "number" : 1 , "name" : "example-1"}
{ "_id" : { "$oid" : "id"} , "number" : 2 , "name" : "example-2"}
{ "_id" : { "$oid" : "id"} , "number" : 3 , "name" : "example-3"}
{ "_id" : { "$oid" : "id"} , "number" : 5 , "name" : "example-5"}

3. найти () и логический

3.1 $and example – get documents where number = 2 and name = 'example-2'.

    BasicDBObject andQuery = new BasicDBObject();
    List obj = new ArrayList();
    obj.add(new BasicDBObject("number", 2));
    obj.add(new BasicDBObject("name", "example-2"));
    andQuery.put("$and", obj);

    System.out.println(andQuery.toString());

    DBCursor cursor = collection.find(andQuery);
    while (cursor.hasNext()) {
        System.out.println(cursor.next());
    }

Выход 

{ "$and" : [ { "number" : 2} , { "name" : "example-2"}]}

{ "_id" : { "$oid" : "id"} , "number" : 2 , "name" : "example-2"}

4. найти () и регулярное выражение

Найти документ с шаблоном регулярного выражения.

4.1 $regex example – get documents where name like pattern 'Mky.*-[1-3]', case insensitive.

    BasicDBObject regexQuery = new BasicDBObject();
    regexQuery.put("name",
        new BasicDBObject("$regex", "Mky.*-[1-3]")
        .append("$options", "i"));

    System.out.println(regexQuery.toString());

    DBCursor cursor = collection.find(regexQuery);
    while (cursor.hasNext()) {
        System.out.println(cursor.next());
    }

Выход 

{ "name" : { "$regex" : "Mky.*-[1-3]" , "$options" : "i"}}

{ "_id" : { "$oid" : "515ad59e3004c89329c7b259"} , "number" : 1 , "name" : "example-1"}
{ "_id" : { "$oid" : "515ad59e3004c89329c7b25a"} , "number" : 2 , "name" : "example-2"}
{ "_id" : { "$oid" : "515ad59e3004c89329c7b25b"} , "number" : 3 , "name" : "example-3"}

There are more…
Прочтите этотMongoDB operator documentation для получения полного набора операторов запросов, поддерживаемых в MongoDB.

5. Полный пример 

package com.example.core;

import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.Mongo;
import com.mongodb.MongoException;

/**
 * Java MongoDB : Query document
 *
 * @author example
 *
 */
public class QueryApp {

    public static void insertDummyDocuments(DBCollection collection) {

        List list = new ArrayList();

        Calendar cal = Calendar.getInstance();

        for (int i = 1; i <= 5; i++) {

            BasicDBObject data = new BasicDBObject();
            data.append("number", i);
            data.append("name", "example-" + i);
            // data.append("date", cal.getTime());

            // +1 day
            cal.add(Calendar.DATE, 1);

            list.add(data);

        }

        collection.insert(list);

    }

    public static void main(String[] args) {

    try {

      Mongo mongo = new Mongo("localhost", 27017);
      DB db = mongo.getDB("yourdb");

      // get a single collection
      DBCollection collection = db.getCollection("dummyColl");

      insertDummyDocuments(collection);

      System.out.println("1. Find first matched document");
      DBObject dbObject = collection.findOne();
      System.out.println(dbObject);

      System.out.println("\n1. Find all matched documents");
      DBCursor cursor = collection.find();
      while (cursor.hasNext()) {
        System.out.println(cursor.next());
      }

      System.out.println("\n1. Get 'name' field only");
      BasicDBObject allQuery = new BasicDBObject();
      BasicDBObject fields = new BasicDBObject();
      fields.put("name", 1);

      DBCursor cursor2 = collection.find(allQuery, fields);
      while (cursor2.hasNext()) {
        System.out.println(cursor2.next());
      }

      System.out.println("\n2. Find where number = 5");
      BasicDBObject whereQuery = new BasicDBObject();
      whereQuery.put("number", 5);
      DBCursor cursor3 = collection.find(whereQuery);
      while (cursor3.hasNext()) {
        System.out.println(cursor3.next());
      }

      System.out.println("\n2. Find where number in 2,4 and 5");
      BasicDBObject inQuery = new BasicDBObject();
      List list = new ArrayList();
      list.add(2);
      list.add(4);
      list.add(5);
      inQuery.put("number", new BasicDBObject("$in", list));
      DBCursor cursor4 = collection.find(inQuery);
      while (cursor4.hasNext()) {
        System.out.println(cursor4.next());
      }

      System.out.println("\n2. Find where 5 > number > 2");
      BasicDBObject gtQuery = new BasicDBObject();
      gtQuery.put("number", new BasicDBObject("$gt", 2).append("$lt", 5));
      DBCursor cursor5 = collection.find(gtQuery);
      while (cursor5.hasNext()) {
        System.out.println(cursor5.next());
      }

      System.out.println("\n2. Find where number != 4");
      BasicDBObject neQuery = new BasicDBObject();
      neQuery.put("number", new BasicDBObject("$ne", 4));
      DBCursor cursor6 = collection.find(neQuery);
      while (cursor6.hasNext()) {
        System.out.println(cursor6.next());
      }

      System.out.println("\n3. Find when number = 2 and name = 'example-2' example");
      BasicDBObject andQuery = new BasicDBObject();

      List obj = new ArrayList();
      obj.add(new BasicDBObject("number", 2));
      obj.add(new BasicDBObject("name", "example-2"));
      andQuery.put("$and", obj);

      System.out.println(andQuery.toString());

      DBCursor cursor7 = collection.find(andQuery);
      while (cursor7.hasNext()) {
        System.out.println(cursor7.next());
      }

      System.out.println("\n4. Find where name = 'Mky.*-[1-3]', case sensitive example");
      BasicDBObject regexQuery = new BasicDBObject();
      regexQuery.put("name",
        new BasicDBObject("$regex", "Mky.*-[1-3]")
                    .append("$options", "i"));

      System.out.println(regexQuery.toString());

      DBCursor cursor8 = collection.find(regexQuery);
      while (cursor8.hasNext()) {
        System.out.println(cursor8.next());
      }

      collection.drop();

      System.out.println("Done");

     } catch (UnknownHostException e) {
        e.printStackTrace();
     } catch (MongoException e) {
        e.printStackTrace();
     }

    }
}

Готово.

Рекомендации

  1. Краткое руководство по операторам запросов, обновлений и проекций

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