Question

我在mongodb tutorial for java中发现了如何从mongo集合中查询，但他们使用的'validators' => array( 'invokables' => array( //'emailExist' => 'Application\MyValidation\EmailExistValidator', ), 'factories' => array( 'emailExist' => function ($vm) { $serviceLocator = $vm->getServiceLocator(); $emailExistValidator = new \Application\MyValidation\EmailExistValidator(); $doctrineEntityManager = $serviceLocator->get('Doctrine\ORM\EntityManager'); $emailExistValidator->setObjectManager($doctrineEntityManager); return $emailExistValidator; }, ), ),对我不起作用！你知道如何使用mongo和java过滤集合中的文档吗？

这是我的尝试：

eq

我想要类似的东西：

package Database;

import org.bson.Document;

import com.mongodb.MongoClient;
import com.mongodb.MongoClientURI;
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;

public class StackOverflow {

    public static void main(String[] args) {

        // insert something to mongo:
        final String URI = "mongodb://localhost:27017";
        final String DB = "StackOverflowQuestion";
        final String COLLECTION = "eqDoesntExcist";

        MongoClientURI connection = new MongoClientURI(URI);
        MongoClient mongo = new MongoClient(connection);
        MongoDatabase database = mongo.getDatabase(DB);
        MongoCollection<Document> collection =  database.getCollection(COLLECTION);

        Document doc = new Document("name", "Troy").append("height", 185);
        collection.insertOne(doc);

        doc = new Document("name", "Ann").append("height", 175);
        collection.insertOne(doc);

        // read something from mongo
        FindIterable<Document> findIt = collection.find(eq("name", "Troy"));
        // ERROR!!! the method eq(String, String) is undefined!

        mongo.close();

    }

}

Answer 1

您可以使用eq Filter作为：

 Bson bsonFilter = Filters.eq("name", "Troy");
 FindIterable<Document> findIt = collection.find(bsonFilter);

或者让它看起来像doc建议的方式包含方法调用的静态导入Filters.eq

import static com.mongodb.client.model.Filters.eq;

并进一步使用与您相同的代码：

FindIterable<Document> findIt = collection.find(eq("name", "Troy")); // static import is the key to such syntax

Answer 2

你不能这样做：

collection.find(eq("name", "Troy"));

因为编译器会在您的班级StackOverflow中使用名为eq的方法，而这不是您需要的方法..

您要查找的内容在Filter class

中定义

public static <TItem> Bson eq(String fieldName, Item value)

所以它可能是

collection.find(Filters.eq("name", "Troy"));

为什么mongo-java-driver不存在eq？

2 个答案: