我正在使用 mongodb java 驱动程序 3.4。
mongodb数据库中文档按照以下结构保存:
{
"_id" : ObjectId("595a9fc4fe3f36402b7edf0e"),
"id" : "123",
"priceInfo" : [
{object1: value1}, {object2: value2}, {object3: value3}
]
}
为了检索具有特定 id 的文档的“priceInfo”数组,我编写了以下代码:
collection.find(eq("id", id)).first().projection(fields(include("priceInfo"), excludeId()));
我根据文档编写了这段代码,您可以在这里找到:
http://mongodb.github.io/mongo-java-driver/3.4/javadoc/?com/mongodb/client/model/Projections.html http://mongodb.github.io/mongo-java-driver/3.4/javadoc/?com/mongodb/client/model/Projections.html
问题是我的 IDE 不接受此代码。
它给我以下错误指示:
我不知道为什么这段代码不起作用。起初,IDE 建议包含几个类 - 我照做了。但之后我仍然收到错误指示,即您在上面看到的错误指示。
代码有什么问题吗?如何检索 ID 为 id 的文档的 PriceInfo 数组?
********************************更新***************** ******************
根据要求,这是全班同学:
package DatabaseAccess;
import Models.GasStation;
import com.mongodb.MongoClient;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import static com.mongodb.client.model.Filters.eq;
import static com.mongodb.client.model.Projections.excludeId;
import static com.mongodb.client.model.Projections.fields;
import static com.mongodb.client.model.Projections.include;
import com.mongodb.client.model.Updates;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.logging.Level;
import org.bson.Document;
public class databaseAccess {
private final String DB_HOST = "localhost";
private final int DB_PORT = 27017;
private final String DB_NAME = "db1";
private final String DB_COLLECTION = "prices";
private final MongoClient mongoClient;
private final MongoDatabase database;
private final MongoCollection<Document> collection;
public databaseAccess(){
mongoClient = new MongoClient(DB_HOST, DB_PORT);
database = mongoClient.getDatabase(DB_NAME);
collection = database.getCollection(DB_COLLECTION);
}
public String readFromDB(String id){
collection.find(eq("id", id)).first().projection(fields(include("priceInfo"), excludeId()));
return null;
}
}