Java操作MongoDB的例子（一）
Java操作MongoDB的例子（一）
在本章中，我们将学习使用JDBC驱动程序连接MongoDB 。
驱动安装
在Java程序中开始使用MongoDB之前，需要确保在计算机上设置了MongoDB JDBC驱动程序和Java。您可以查看Java教程以了解计算机上的Java安装。现在，让我们检查如何设置MongoDB JDBC驱动程序。
您需要从https://github.com/mongodb/mongo-java-driver下载MongoDB的JDBC驱动。请确保下载它的最新版本。
您需要将mongo.jar包含在java项目的classpath中。
连接数据库
要连接数据库，需要指定数据库名称，如果数据库不存在，MongoDB将自动创建它。
import com.mongodb.client.MongoDatabase;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
public class ConnectToDB {
public static void main( String args[] ) {
// Creating a Mongo client
MongoClient mongo = new MongoClient( "localhost" , 27017 );
// Creating Credentials
MongoCredential credential;
credential = MongoCredential.createCredential("sampleUser", "myDb",
"password".toCharArray());
System.out.println("Connected to the database successfully");
// Accessing the database
MongoDatabase database = mongo.getDatabase("myDb");
System.out.println("Credentials ::"+ credential);
}
}现在，让我们编译并运行上面的程序来创建我们的数据库myDb，如下所示。
$javac ConnectToDB.java $java ConnectToDB
执行时，上面的程序会给出以下输出。
Connected to the database successfully
Credentials ::MongoCredential{
mechanism = null,
userName = 'sampleUser',
source = 'myDb',
password = <hidden>,
mechanismProperties = {}
}创建一个集合
要创建集合，请使用com.mongodb.client.MongoDatabase类的createCollection()方法。
import com.mongodb.client.MongoDatabase;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
public class CreatingCollection {
public static void main( String args[] ) {
// Creating a Mongo client
MongoClient mongo = new MongoClient( "localhost" , 27017 );
// Creating Credentials
MongoCredential credential;
credential = MongoCredential.createCredential("sampleUser", "myDb",
"password".toCharArray());
System.out.println("Connected to the database successfully");
//Accessing the database
MongoDatabase database = mongo.getDatabase("myDb");
//Creating a collection
database.createCollection("sampleCollection");
System.out.println("Collection created successfully");
}
}编译运行时，上面的程序会给出以下结果-
Connected to the database successfully Collection created successfully
获取/选择集合
要从数据库中获取/选择集合，请使用com.mongodb.client.MongoDatabase类的getCollection()方法。
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
public class selectingCollection {
public static void main( String args[] ) {
// Creating a Mongo client
MongoClient mongo = new MongoClient( "localhost" , 27017 );
// Creating Credentials
MongoCredential credential;
credential = MongoCredential.createCredential("sampleUser", "myDb",
"password".toCharArray());
System.out.println("Connected to the database successfully");
// Accessing the database
MongoDatabase database = mongo.getDatabase("myDb");
// Creating a collection
System.out.println("Collection created successfully");
// Retieving a collection
MongoCollection<Document> collection = database.getCollection("myCollection");
System.out.println("Collection myCollection selected successfully");
}
}编译运行时，上面的程序会给出以下结果-
Connected to the database successfully Collection created successfully Collection myCollection selected successfully
插入一个文档
要在MongoDB中插入文档，请使用com.mongodb.client.MongoCollection类的insert()方法。
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
public class InsertingDocument {
public static void main( String args[] ) {
// Creating a Mongo client
MongoClient mongo = new MongoClient( "localhost" , 27017 );
// Creating Credentials
MongoCredential credential;
credential = MongoCredential.createCredential("sampleUser", "myDb",
"password".toCharArray());
System.out.println("Connected to the database successfully");
// Accessing the database
MongoDatabase database = mongo.getDatabase("myDb");
// Retrieving a collection
MongoCollection<Document> collection = database.getCollection("sampleCollection");
System.out.println("Collection sampleCollection selected successfully");
Document document = new Document("title", "MongoDB")
.append("id", 1)
.append("description", "database")
.append("likes", 100)
.append("url", "http://www.tutorialspoint.com/mongodb/")
.append("by", "tutorials point");
collection.insertOne(document);
System.out.println("Document inserted successfully");
}
}编译运行时，上面的程序会给出以下结果-
Connected to the database successfully Collection sampleCollection selected successfully Document inserted successfully
检索所有文档
要从集合中选择所有文档，请使用com.mongodb.client.MongoCollection类的find()方法。此方法返回游标，因此需要迭代此游标。
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import java.util.Iterator;
import org.bson.Document;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
public class RetrievingAllDocuments {
public static void main( String args[] ) {
// Creating a Mongo client
MongoClient mongo = new MongoClient( "localhost" , 27017 );
// Creating Credentials
MongoCredential credential;
credential = MongoCredential.createCredential("sampleUser", "myDb",
"password".toCharArray());
System.out.println("Connected to the database successfully");
// Accessing the database
MongoDatabase database = mongo.getDatabase("myDb");
// Retrieving a collection
MongoCollection<Document> collection = database.getCollection("sampleCollection");
System.out.println("Collection sampleCollection selected successfully");
// Getting the iterable object
FindIterable<Document> iterDoc = collection.find();
int i = 1;
// Getting the iterator
Iterator it = iterDoc.iterator();
while (it.hasNext()) {
System.out.println(it.next());
i++;
}
}
}编译运行时，上面的程序会给出以下结果-
Document{{
_id = 5967745223993a32646baab8,
title = MongoDB,
id = 1,
description = database,
likes = 100,
url = http://www.tutorialspoint.com/mongodb/, by = tutorials point
}}
Document{{
_id = 7452239959673a32646baab8,
title = RethinkDB,
id = 2,
description = database,
likes = 200,
url = http://www.tutorialspoint.com/rethinkdb/, by = tutorials point
}}未完待续。。。