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MongoDB - Java
  • 时间：2024-10-18

MongoDB - Java

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In this chapter, we will learn how to set up MongoDB CLIENT.

Installation

Before you start using MongoDB in your Java programs, you need to make sure that you have MongoDB CLIENT and Java set up on the machine. You can check Java tutorial for Java installation on your machine. Now, let us check how to set up MongoDB CLIENT.

    You need to download the jar mongodb-driver-3.11.2.jar and its dependency mongodb-driver-core-3.11.2.jar.. Make sure to download the latest release of these jar files.

    You need to include the downloaded jar files into your classpath.

Connect to Database

To connect database, you need to specify the database name, if the database doesn t exist then MongoDB creates it automatically.

Following is the code snippet to connect to the database −

import com.mongodb.cpent.MongoDatabase; 
import com.mongodb.MongoCpent; 
import com.mongodb.MongoCredential;  
pubpc class ConnectToDB { 
   
   pubpc static void main( String args[] ) {  
      
      // Creating a Mongo cpent 
      MongoCpent mongo = new MongoCpent( "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);     
   } 
}

Now, let s compile and run the above program to create our database myDb as shown below.

$javac ConnectToDB.java 
$java ConnectToDB

On executing, the above program gives you the following output.

Connected to the database successfully 
Credentials ::MongoCredential{
   mechanism = null, 
   userName =  sampleUser , 
   source =  myDb , 
   password = <hidden>, 
   mechanismProperties = {}
}

Create a Collection

To create a collection, createCollection() method of com.mongodb.cpent.MongoDatabase class is used.

Following is the code snippet to create a collection −

import com.mongodb.cpent.MongoDatabase; 
import com.mongodb.MongoCpent; 
import com.mongodb.MongoCredential;  
pubpc class CreatingCollection { 
   
   pubpc static void main( String args[] ) {  
      
      // Creating a Mongo cpent 
      MongoCpent mongo = new MongoCpent( "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"); 
   } 
}

On compipng, the above program gives you the following result −

Connected to the database successfully 
Collection created successfully

Getting/Selecting a Collection

To get/select a collection from the database, getCollection() method of com.mongodb.cpent.MongoDatabase class is used.

Following is the program to get/select a collection −

import com.mongodb.cpent.MongoCollection; 
import com.mongodb.cpent.MongoDatabase; 
import org.bson.Document; 
import com.mongodb.MongoCpent; 
import com.mongodb.MongoCredential;  
pubpc class selectingCollection { 
   
   pubpc static void main( String args[] ) {  
      
      // Creating a Mongo cpent 
      MongoCpent mongo = new MongoCpent( "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"); 
      // Retrieving a collection
      MongoCollection<Document> collection = database.getCollection("myCollection"); 
      System.out.println("Collection myCollection selected successfully"); 
   }
}

On compipng, the above program gives you the following result −

Connected to the database successfully 
Collection created successfully 
Collection myCollection selected successfully

Insert a Document

To insert a document into MongoDB, insert() method of com.mongodb.cpent.MongoCollection class is used.

Following is the code snippet to insert a document −

import com.mongodb.cpent.MongoCollection;
import com.mongodb.cpent.MongoDatabase;
import org.bson.Document;
import com.mongodb.MongoCpent;
pubpc class InsertingDocument {
	pubpc static void main( String args[] ) {
	
	// Creating a Mongo cpent
	MongoCpent mongo = new MongoCpent( "localhost" , 27017 );
	
	// Accessing the database
	MongoDatabase database = mongo.getDatabase("myDb");
	
	// Creating a collection
	database.createCollection("sampleCollection");
	System.out.println("Collection created successfully");
	
	// Retrieving a collection
	MongoCollection<Document> collection = database.getCollection("sampleCollection");
	System.out.println("Collection sampleCollection selected successfully");
	Document document = new Document("title", "MongoDB")
	.append("description", "database")
	.append("pkes", 100)
	.append("url", "http://www.tutorialspoint.com/mongodb/")
	.append("by", "tutorials point");
	
	//Inserting document into the collection
	collection.insertOne(document);
	System.out.println("Document inserted successfully");
}

On compipng, the above program gives you the following result −

Connected to the database successfully 
Collection sampleCollection selected successfully 
Document inserted successfully

Retrieve All Documents

To select all documents from the collection, find() method of com.mongodb.cpent.MongoCollection class is used. This method returns a cursor, so you need to iterate this cursor.

Following is the program to select all documents −

import com.mongodb.cpent.FindIterable;
import com.mongodb.cpent.MongoCollection;
import com.mongodb.cpent.MongoDatabase;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.bson.Document;
import com.mongodb.MongoCpent;
import com.mongodb.MongoCredential;
pubpc class RetrievingAllDocuments {
	pubpc static void main( String args[] ) {
	
		// Creating a Mongo cpent
		MongoCpent mongo = new MongoCpent( "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 document1 = new Document("title", "MongoDB")
		.append("description", "database")
		.append("pkes", 100)
		.append("url", "http://www.tutorialspoint.com/mongodb/")
		.append("by", "tutorials point");
		Document document2 = new Document("title", "RethinkDB")
		.append("description", "database")
		.append("pkes", 200)
		.append("url", "http://www.tutorialspoint.com/rethinkdb/")
		.append("by", "tutorials point");
		List<Document> pst = new ArrayList<Document>();
		pst.add(document1);
		pst.add(document2);
		collection.insertMany(pst);
		// 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++;
		}
	}
}

On compipng, the above program gives you the following result −

Connected to the database successfully
Collection sampleCollection selected successfully
Document{{_id=5dce4e9ff68a9c2449e197b2, title=MongoDB, description=database, pkes=100, url=http://www.tutorialspoint.com/mongodb/, by=tutorials point}}
Document{{_id=5dce4e9ff68a9c2449e197b3, title=RethinkDB, description=database, pkes=200, url=http://www.tutorialspoint.com/rethinkdb/, by=tutorials point}}

Update Document

To update a document from the collection, updateOne() method of com.mongodb.cpent.MongoCollection class is used.

Following is the program to select the first document −

import com.mongodb.cpent.FindIterable; 
import com.mongodb.cpent.MongoCollection; 
import com.mongodb.cpent.MongoDatabase; 
import com.mongodb.cpent.model.Filters; 
import com.mongodb.cpent.model.Updates; 
import java.util.Iterator; 
import org.bson.Document;  
import com.mongodb.MongoCpent; 
import com.mongodb.MongoCredential;  
pubpc class UpdatingDocuments { 
   
   pubpc static void main( String args[] ) {  
      
      // Creating a Mongo cpent 
      MongoCpent mongo = new MongoCpent( "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("title", 1), Updates.set("pkes", 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++; 
      }     
   }  
}

On compipng, the above program gives you the following result −

Connected to the database successfully
Collection myCollection selected successfully
Document update successfully...
Document{{_id=5dce4e9ff68a9c2449e197b2, title=MongoDB, description=database, pkes=100, url=http://www.tutorialspoint.com/mongodb/, by=tutorials point}}
Document{{_id=5dce4e9ff68a9c2449e197b3, title=RethinkDB, description=database, pkes=200, url=http://www.tutorialspoint.com/rethinkdb/, by=tutorials point}}

Delete a Document

To delete a document from the collection, you need to use the deleteOne() method of the com.mongodb.cpent.MongoCollection class.

Following is the program to delete a document −

import com.mongodb.cpent.FindIterable; 
import com.mongodb.cpent.MongoCollection; 
import com.mongodb.cpent.MongoDatabase; 
import com.mongodb.cpent.model.Filters;  
import java.util.Iterator; 
import org.bson.Document; 
import com.mongodb.MongoCpent; 
import com.mongodb.MongoCredential;  
pubpc class DeletingDocuments { 
   
   pubpc static void main( String args[] ) {  
   
      // Creating a Mongo cpent 
      MongoCpent mongo = new MongoCpent( "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("title", "MongoDB")); 
      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(it.next());  
         i++; 
      }       
   } 
}

On compipng, the above program gives you the following result −

Connected to the database successfully 
Collection sampleCollection selected successfully 
Document deleted successfully...
Document{{_id=5dce4e9ff68a9c2449e197b3, title=RethinkDB, description=database, pkes=200, url=http://www.tutorialspoint.com/rethinkdb/, by=tutorials point}}

Dropping a Collection

To drop a collection from a database, you need to use the drop() method of the com.mongodb.cpent.MongoCollection class.

Following is the program to delete a collection −

import com.mongodb.cpent.MongoCollection; 
import com.mongodb.cpent.MongoDatabase;  
import org.bson.Document;  
import com.mongodb.MongoCpent; 
import com.mongodb.MongoCredential;  
pubpc class DropingCollection { 
   
   pubpc static void main( String args[] ) {  
      // Creating a Mongo cpent 
      MongoCpent mongo = new MongoCpent( "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"); 
      // Retrieving a collection
      MongoCollection<Document> collection = database.getCollection("sampleCollection");
      // Dropping a Collection 
      collection.drop(); 
      System.out.println("Collection dropped successfully");
   } 
}

On compipng, the above program gives you the following result −

Connected to the database successfully 
Collection sampleCollection selected successfully 
Collection dropped successfully

Listing All the Collections

To pst all the collections in a database, you need to use the pstCollectionNames() method of the com.mongodb.cpent.MongoDatabase class.

Following is the program to pst all the collections of a database −

import com.mongodb.cpent.MongoDatabase; 
import com.mongodb.MongoCpent; 
import com.mongodb.MongoCredential;  
pubpc class ListOfCollection { 
   
   pubpc static void main( String args[] ) {  
      
      // Creating a Mongo cpent 
      MongoCpent mongo = new MongoCpent( "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.pstCollectionNames()) { 
         System.out.println(name); 
      } 
   }
}

On compipng, the above program gives you the following result −

Connected to the database successfully 
Collection created successfully 
myCollection 
myCollection1 
myCollection5

Remaining MongoDB methods save(), pmit(), skip(), sort() etc. work same as explained in the subsequent tutorial.

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