在本章中，我们将学习如何设置MongoDB JDBC驱动程序.
在Java程序中开始使用MongoDB之前，您需要确保在计算机上设置了MongoDB JDBC驱动程序和Java.您可以在计算机上查看Java安装Java教程.现在，让我们检查如何设置MongoDB JDBC驱动程序.
您需要从路径
您需要将mongo.jar包含在类路径中.
要连接数据库，需要指定数据库名称，如果数据库不存在则MongoDB创建它自动.
以下是连接到数据库的代码片段 :
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，上述程序为您提供以下输出.
Connected to the database successfully
Credentials ::MongoCredential{
mechanism = null,
userName = 'sampleUser',
source = 'myDb',
password = <hidden>,
mechanismProperties = {}
}要创建集合 com的 createCollection()方法.使用了mongodb.client.MongoDatabase 类.
以下是创建集合的代码片段 :
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");
}
}编译时，上述程序会给你以下结果 :
Connected to the database successfully Collection created successfully
要从数据库中获取/选择集合，使用 com.mongodb.client.MongoDatabase 类的 getCollection()方法.
以下是获取/选择集合的程序 :
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");
}
}编译时，上述程序会给你以下结果 :
Connected to the database successfully Collection created successfully Collection myCollection selected successfully
要将文档插入MongoDB，使用 com.mongodb.client.MongoCollection 类的 insert()方法.
以下是插入文档的代码片段 :
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.it1352.com/")
.append("by", "tutorials point");
collection.insertOne(document);
System.out.println("Document inserted successfully");
}
}编译时，上述程序会给你以下结果 :
Connected to the database successfully Collection sampleCollection selected successfully Document inserted successfully
要从集合中选择所有文档， com.mongodb.client.MongoCollection 类的 find()方法是用过的.此方法返回一个游标，因此您需要迭代此游标.
以下是选择所有文档的程序 :
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++;
}
}
}编译时，上述程序会给你以下结果 :
Document{{
_id = 5967745223993a32646baab8,
title = MongoDB,
id = 1,
description = database,
likes = 100,
url = http://www.it1352.com/OnLineTutorial/Index, by=it1352
}}
Document{{
_id = 7452239959673a32646baab8,
title = RethinkDB,
id = 2,
description = database,
likes = 200,
url = http://www.it1352.com/OnLineTools/Index, by=it1352
}}更新使用 com.mongodb.client.MongoCollection 类的集合 updateOne()方法中的文档.
以下是程序选择第一个文件 :
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.Filters;
import com.mongodb.client.model.Updates;
import java.util.Iterator;
import org.bson.Document;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
public class UpdatingDocuments {
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 myCollection selected successfully");
collection.updateOne(Filters.eq("id", 1), Updates.set("likes", 150));
System.out.println("Document update successfully...");
// Retrieving the documents after updation
// 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++;
}
}
}编译时，上述程序会给你以下结果 :
Document update successfully...
Document {{
_id = 5967745223993a32646baab8,
title = MongoDB,
id = 1,
description = database,
likes = 150,
url = http://www.it1352.com/OnLineTutorial/Index, by =it1352
}}要从集合中删除文档，您需要使用 deleteOne( com.mongodb.client.MongoCollection 类的方法.
以下是删除文件的程序 :
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.Filters;
import java.util.Iterator;
import org.bson.Document;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
public class DeletingDocuments {
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");
// Deleting the documents
collection.deleteOne(Filters.eq("id", 1));
System.out.println("Document deleted successfully...");
// Retrieving the documents after updation
// 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("Inserted Document: "+i);
System.out.println(it.next());
i++;
}
}
}编译时，上述程序会给你以下结果 :
Connected to the database successfully Collection sampleCollection selected successfully Document deleted successfully...
要从数据库中删除集合，您需要使用的drop()方法> com.mongodb.client.MongoCollection class.
以下是删除集合的程序 :
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
public class DropingCollection {
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("Collections created successfully");
// Retieving a collection
MongoCollection<Document> collection = database.getCollection("sampleCollection");
// Dropping a Collection
collection.drop();
System.out.println("Collection dropped successfully");
}
}编译时，上述程序会给你以下结果 :
Connected to the database successfully Collection sampleCollection selected successfully Collection dropped successfully
要列出数据库中的所有集合，您需要使用 com.mongodb.client的 listCollectionNames()方法.MongoDatabase 类.
以下是列出数据库所有集合的程序 :
import com.mongodb.client.MongoDatabase;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
public class ListOfCollection {
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("Collection created successfully");
for (String name : database.listCollectionNames()) {
System.out.println(name);
}
}
}编译时，上述程序会给你以下结果 :
Connected to the database successfully Collection created successfully myCollection myCollection1 myCollection5
剩余的MongoDB方法 save()，limit()，skip()，sort()等，与后续教程中的说明相同.
