Java Mongodb 简明教程
Java & MongoDB - Select Document
若要选择一个集合中的文档,可以使用 collection.find() 或 collection.find(filter) 方法选择一个集合的文档。
// find all documents of a collection
collection.find();
// find document(s) fulfiling the filter criteria
collection.find(filter);
Example
以下是显示选定文档的代码片段 −
import java.util.ArrayList;
import java.util.List;
import org.bson.Document;
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.Filters;
public class Tester {
public static void main(String[] args) {
// Creating a Mongo client
MongoClient mongoClient = MongoClients.create("mongodb://localhost:27017");
MongoDatabase database = mongoClient.getDatabase("myDb");
// Get the collection
MongoCollection<Document> collection = database.getCollection("sampleCollection");
// Find all documents
FindIterable<Document> allDocuments = collection.find();
for (Document document : allDocuments) {
System.out.println(document);
}
System.out.println("***Selected Document***");
// Select a particular document
FindIterable<Document> documents = collection.find(Filters.eq("First_Name","Mahesh"));
for (Document document : documents) {
System.out.println(document);
}
}
}
现在,我们按照以下步骤编译并运行上述程序。
$javac Tester.java
$java Tester
Output
在执行上述程序时,您将得到以下输出。
Document{{_id=60b70d426214461f10ac5c99, First_Name=Mahesh, Last_Name=Parashar, Date_Of_Birth=1990-08-21, e_mail=mahesh_parashar.123@gmail.com, phone=9034343345}}
Document{{_id=60b70d426214461f10ac5c9a, First_Name=Radhika, Last_Name=Sharma, Date_Of_Birth=1995-09-26, e_mail=radhika_sharma.123@gmail.com, phone=9000012345}}
Document{{_id=60b70d426214461f10ac5c9b, First_Name=Rachel, Last_Name=Christopher, Date_Of_Birth=1990-02-16, e_mail=Rachel_Christopher.123@gmail.com, phone=9000054321}}
Document{{_id=60b70d426214461f10ac5c9c, First_Name=Fathima, Last_Name=Sheik, Date_Of_Birth=1990-02-16, e_mail=Fathima_Sheik.123@gmail.com, phone=9000054321}}
********
Document{{_id=60b70d426214461f10ac5c99, First_Name=Mahesh, Last_Name=Parashar, Date_Of_Birth=1990-08-21, e_mail=mahesh_parashar.123@gmail.com, phone=9034343345}}