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What Is Objectid in Mongodb and How to Generate It Manually

MongoDB is a document-oriented NoSQL database used for high volume data storage. Instead of using tables and rows as in the traditional relational databases, MongoDB makes use of collections and documents.You can read more about MongoDB here.What are documents and collections?Collection: A collection is a group of MongoDB documents, and is similar to a table in a SQL(RDBMS) Database. A collection exists within a single database. Collections do not enforce a schema(structure). Documents within a collection can have different fields. Typically, all documents in a collection are of a similar or related purpose. Documents: A document is a set of key-value pairs. Documents have dynamic schema(structure). Dynamic schema means that documents in the same collection do not need to have the same set of fields or structure, and common fields in a collection's documents may hold different types of data.An example of a MongoDB document is shown below:{    _id: ObjectId(7df78ad8902ce46d)    title: 'Awesome Post',       description: 'This is an awesome post',    tags: ['tours', 'photography'],    likes: 100,      comments: [       {          user:'user1',          message: 'My first comment',          dateCreated: new Date(2011,1,20,2,15),          like: 0         },       {          user:'user2',          message: 'My second comments',          dateCreated: new Date(2011,1,25,7,45),          like: 5       }    ] }_id is a 12 bytes hexadecimal number which assures the uniqueness of every document. It is called ObjectId.In this blog we are going to learn about MongoDB, ObjectId and how to generate it manually.Why use MongoDB?It is document oriented: The document data model is a powerful way to store and retrieve data that allows developers to move fast.High performance: MongoDB’s horizontal, scale-out architecture can support huge volumes of both data and traffic.Data Representation in JSON or BSON. An example of a JSON object is given below.{   "name" :  "Carlos Smith",   "title" : "Product Manager",   "location" : "New York, NY",   "twitter" : "@MongoDB",   "facebook" : "@MongoDB" }You can read more about the use cases of MongoDB here.What is the difference between MySQL and MongoDB?The major and the key differences between MySQL and MongoDB are listed here:MongoDB is an open-source database developed by MongoDB, Inc. MongoDB stores data in JSON-like documents that can vary in structure. It is a popular NoSQL database.MySQL is a popular open-source relational database management system (RDBMS) that is developed, distributed and supported by Oracle Corporation. MySQL uses tables to store the data.You can read more about the differences here.How to install MongoDB locally?Let's go through the installation separately for Windows and Linux operating systems.Windows: Navigate to the below mentioned link and click on the download button to download the zip file, as you can see in the image.Link to download MongoDB.You can unzip and run the file to install MongoDB for Windows.Linux: You can simply run the below command inside the terminal to install MongoDB.Command: sudo apt-get install mongodbNow, run the below command inside the command prompt, powershell or terminal to start MongoDB shell where we can create the Object IDs for this blog. Command: mongoIt's important to know that MongoDB uses BSON format to store data.Difference between JSON and BSON:As we have already seen how JSON looks, now let's take a look at BSON and understand the differences between JSON and BSON.BSON stands for binary JSON (a superset of JSON with some more data types, most importantly binary byte array).You can read more about the differences here.What is ObjectId in MongoDB?As you see, in the example of a MongoDB document the _id field is called Object ID. MongoDB uses ObjectIds as the default value of _id field of each document, which is generated during the creation of any document.Object ID is treated as the primary key within any MongoDB collection. It is a unique identifier for each document or record. Syntax: ObjectId(<hexadecimal>).An ObjectId is a 12-byte BSON type hexadecimal string having the structure as shown in the example below.Example: ObjectId("6009c0eee65f6dce28fb3e50") The first 4 bytes are a timestamp value, representing the ObjectId’s creation, measured in seconds since the Unix epoch.Next 5-bytes represent a  random value.Note: Object ID is a unique identifier for each record which is created by declaring ObjectId as a method, as you will now see. Do not get confused between Object ID and ObjectId.Creating a new ObjectId:To create a new Object ID manually within the MongoDB you can declare ObjectId as a method. In the below image you can observe that we are declaring a variable having ObjectId method as a value. It will return a unique hexadecimal which we can store in a variable named myObjectId.Command: myObjectId = ObjectId()In this example, the value of myObjectId would be: ObjectId("6009cb85e65f6dce28fb3e51").In the above image, you can observe that each time it is returning a unique hexadecimal value.Specify a Hexadecimal String:Sometimes you want to define your own unique hexadecimal value, and MongoDB allows you to perform this action. In the above example the hexadecimal value is generated.In this scenario, we will define an object ID with a hexadecimal value as a parameter of the ObjectId method.Command: newObjectId = ObjectId("507f1f77bcf86cd799439011")In this example, the value of newObjectId would be: ObjectId("507f1f77bcf86cd799439011").Access the Hexadecimal String:In the above examples we are unable to get the hexadecimal string, as it will return you the whole method having the unique hexadecimal value.To extract the unique hexadecimal as a string from the Object ID, we need to use ‘str’ attribute which is available in ObjectId method.Command: ObjectId("507f191e810c19729de860ea").strIn this example, the value of the ObjectId("507f191e810c19729de860ea").str method returned the hexadecimal string which is inside ObjectId method.Methods available upon ObjectId:Note: We already have newObjectId with us so we can test these methods using the same variable.Method: ObjectId.getTimestamp().Explanation: Returns the timestamp portion of the object as a Date.Command: newObjectId.getTimestamp()This will return the creation time of this document in ISO date format.Method: ObjectId.toString()Explanation: Returns the string representation of the ObjectId(). This string value has the format of ObjectId(<hexadecimal>).Command: newObjectId.toString()This will return the ObjectId(<hexadecimal>) of this document in string format.Method: ObjectId.valueOf()Explanation: Returns the value of the ObjectId() as a lowercase hexadecimal string. This value is the str attribute of the ObjectId() object.Command: newObjectId.valueOf()Note that the returned values of newObjectId.valueOf() and newObjectId.str are the same.What you have learntWhat is MongoDB and why do we use it?Differences between MySQL and MongoDB DatabasesHow to install mongodb locally in Windows and Linux Operating systems.Differences between JSON and BSON documentsWhat is ObjectId and its importance Generating a new ObjectId manually Methods available over Object Id and how to use them.MongoDB is a NoSQL DB that is widely used in the industry, and also easy to learn. Good luck!

What Is Objectid in Mongodb and How to Generate It Manually

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What Is Objectid in Mongodb and How to Generate It Manually

MongoDB is a document-oriented NoSQL database used for high volume data storage. Instead of using tables and rows as in the traditional relational databases, MongoDB makes use of collections and documents.

You can read more about MongoDB here.

What are documents and collections?

  • Collection: A collection is a group of MongoDB documents, and is similar to a table in a SQL(RDBMS) Database. A collection exists within a single database. Collections do not enforce a schema(structure). Documents within a collection can have different fields. Typically, all documents in a collection are of a similar or related purpose. 
  • Documents: A document is a set of key-value pairs. Documents have dynamic schema(structure). Dynamic schema means that documents in the same collection do not need to have the same set of fields or structure, and common fields in a collection's documents may hold different types of data.

An example of a MongoDB document is shown below:

{
   _id: ObjectId(7df78ad8902ce46d)
   title: 'Awesome Post',   
   description: 'This is an awesome post',
   tags: ['tours', 'photography'],
   likes: 100,  
   comments: [
      {
         user:'user1',
         message: 'My first comment',
         dateCreated: new Date(2011,1,20,2,15),
         like: 0  
      },
      {
         user:'user2',
         message: 'My second comments',
         dateCreated: new Date(2011,1,25,7,45),
         like: 5
      }
   ]
}

_id is a 12 bytes hexadecimal number which assures the uniqueness of every document. It is called ObjectId.

In this blog we are going to learn about MongoDB, ObjectId and how to generate it manually.

Why use MongoDB?

  • It is document oriented: The document data model is a powerful way to store and retrieve data that allows developers to move fast.
  • High performance: MongoDB’s horizontal, scale-out architecture can support huge volumes of both data and traffic.

Data Representation in JSON or BSON. An example of a JSON object is given below.

{
  "name" :  "Carlos Smith",
  "title" : "Product Manager",
  "location" : "New York, NY",
  "twitter" : "@MongoDB",
  "facebook" : "@MongoDB"
}

You can read more about the use cases of MongoDB here.

What is the difference between MySQL and MongoDB?

The major and the key differences between MySQL and MongoDB are listed here:

MongoDB is an open-source database developed by MongoDB, Inc. MongoDB stores data in JSON-like documents that can vary in structure. It is a popular NoSQL database.

MySQL is a popular open-source relational database management system (RDBMS) that is developed, distributed and supported by Oracle Corporation. MySQL uses tables to store the data.You can read more about the differences here.

How to install MongoDB locally?

Let's go through the installation separately for Windows and Linux operating systems.

  • Windows: Navigate to the below mentioned link and click on the download button to download the zip file, as you can see in the image.

Link to download MongoDB.

What Is Objectid in Mongodb and How to Generate It Manually

You can unzip and run the file to install MongoDB for Windows.

  • Linux: You can simply run the below command inside the terminal to install MongoDB.
  • Command: sudo apt-get install mongodbWhat Is Objectid in Mongodb and How to Generate It Manually

Now, run the below command inside the command prompt, powershell or terminal to start MongoDB shell where we can create the Object IDs for this blog. 

  • Command: mongo

What Is Objectid in Mongodb and How to Generate It Manually

It's important to know that MongoDB uses BSON format to store data.

Difference between JSON and BSON:

As we have already seen how JSON looks, now let's take a look at BSON and understand the differences between JSON and BSON.

BSON stands for binary JSON (a superset of JSON with some more data types, most importantly binary byte array).

You can read more about the differences here.

What is ObjectId in MongoDB?

  • As you see, in the example of a MongoDB document the _id field is called Object ID. MongoDB uses ObjectIds as the default value of _id field of each document, which is generated during the creation of any document.
  • Object ID is treated as the primary key within any MongoDB collection. It is a unique identifier for each document or record. 
  • Syntax: ObjectId(<hexadecimal>).
  • An ObjectId is a 12-byte BSON type hexadecimal string having the structure as shown in the example below.
    Example: ObjectId("6009c0eee65f6dce28fb3e50") 
  • The first 4 bytes are a timestamp value, representing the ObjectId’s creation, measured in seconds since the Unix epoch.
  • Next 5-bytes represent a  random value.

Note: Object ID is a unique identifier for each record which is created by declaring ObjectId as a method, as you will now see. Do not get confused between Object ID and ObjectId.

Creating a new ObjectId:

To create a new Object ID manually within the MongoDB you can declare ObjectId as a method. In the below image you can observe that we are declaring a variable having ObjectId method as a value. It will return a unique hexadecimal which we can store in a variable named myObjectId.

  • Command: myObjectId = ObjectId()

What Is Objectid in Mongodb and How to Generate It Manually

In this example, the value of myObjectId would be: ObjectId("6009cb85e65f6dce28fb3e51").

In the above image, you can observe that each time it is returning a unique hexadecimal value.

Specify a Hexadecimal String:

Sometimes you want to define your own unique hexadecimal value, and MongoDB allows you to perform this action. In the above example the hexadecimal value is generated.

In this scenario, we will define an object ID with a hexadecimal value as a parameter of the ObjectId method.

  • Command: newObjectId = ObjectId("507f1f77bcf86cd799439011")

What Is Objectid in Mongodb and How to Generate It Manually

In this example, the value of newObjectId would be: ObjectId("507f1f77bcf86cd799439011").

Access the Hexadecimal String:

In the above examples we are unable to get the hexadecimal string, as it will return you the whole method having the unique hexadecimal value.

To extract the unique hexadecimal as a string from the Object ID, we need to use ‘str’ attribute which is available in ObjectId method.

  • Command: ObjectId("507f191e810c19729de860ea").str

What Is Objectid in Mongodb and How to Generate It Manually

In this example, the value of the ObjectId("507f191e810c19729de860ea").str method returned the hexadecimal string which is inside ObjectId method.

Methods available upon ObjectId:

  • Note: We already have newObjectId with us so we can test these methods using the same variable.
  • Method: ObjectId.getTimestamp().
  • Explanation: Returns the timestamp portion of the object as a Date.
  • Command: newObjectId.getTimestamp()

What Is Objectid in Mongodb and How to Generate It Manually

This will return the creation time of this document in ISO date format.

  • Method: ObjectId.toString()
  • Explanation: Returns the string representation of the ObjectId(). This string value has the format of ObjectId(<hexadecimal>).
  • Command: newObjectId.toString()

What Is Objectid in Mongodb and How to Generate It Manually

This will return the ObjectId(<hexadecimal>) of this document in string format.

  • Method: ObjectId.valueOf()
  • Explanation: Returns the value of the ObjectId() as a lowercase hexadecimal string. This value is the str attribute of the ObjectId() object.
  • Command: newObjectId.valueOf()

What Is Objectid in Mongodb and How to Generate It Manually

Note that the returned values of newObjectId.valueOf() and newObjectId.str are the same.

What you have learnt

  • What is MongoDB and why do we use it?
  • Differences between MySQL and MongoDB Databases
  • How to install mongodb locally in Windows and Linux Operating systems.
  • Differences between JSON and BSON documents
  • What is ObjectId and its importance 
  • Generating a new ObjectId manually 
  • Methods available over Object Id and how to use them.

MongoDB is a NoSQL DB that is widely used in the industry, and also easy to learn. Good luck!

KnowledgeHut

KnowledgeHut

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KnowledgeHut is an outcome-focused global ed-tech company. We help organizations and professionals unlock excellence through skills development. We offer training solutions under the people and process, data science, full-stack development, cybersecurity, future technologies and digital transformation verticals.
Website : https://www.knowledgehut.com

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Node.js has a ‘net’ module which provides an asynchronous network API for creating stream-based TCP/IPC servers and clients. It can be accessed using: const net = require('net');  To create a TCP/IPC based server, we use the createServer method. var server = net.createServer(); The ‘server' object is of type net.Server. Let’s explore a few properties, events and methods on this class. First and foremost, the method needed is ‘listen’ which starts the server for listening to connections in async, firing the ‘listening’ event. server.listen(9000, () => {    console.log('opened server on port: ', 9000);  }); To find out on which address a server is running, we can use the address() method on the net.Server instance. If we need to log the port on which the server is running, then we can get this info as well without hardcoding. server.listen(9000, () => {    console.log('opened server on %j', server.address().port);  }); The first parameter of listen is the port in which the server starts listening, and a callback which gets called once it has started listening. A few of the common errors raised are:  ERR_SERVER_ALREADY_LISTEN – server is already listening and hasn’t been closed. EADDRINUSE – another server is already listening on the given port/handle/path. Whenever an error happens, an ‘error’ event is raised. We can hook to it and capture the errors accordingly. server.on('error', (e) => {    if (e.code === 'EADDRINUSE') {      console.log('Address in use, retrying...');      setTimeout(() => {        server.close();        server.listen(PORT, HOST);      }, 1000);    }  }); Whenever a client connects to this server then a 'connection' event is raised and in the callback we can get hold of the client object for communicating data. server.on("connection", (socket) => {    console.log("new client connection is made");  }); The second parameter is actually a callback which has the reference to the connection object, and the client object is of type ‘net.Socket’. To get the details like address and port, we can rely on remoteAddress, and remotePort properties respectively.   server.on("connection", (socket) => {    console.log("Client connection details - ", socket.remoteAddress + ":" + socket.remotePort);  }); Let’s assume that we are developing an application server like bot which needs to take inputs from clients and respond to the client. We can get hold of the client object and send messages to it from the server. As soon as the client is connected, we can send a sample return message on successful connection. server.on("connection", (socket) => {    console.log("Client connection details - ", socket.remoteAddress + ":" + socket.remotePort);    socket.write('SERVER: Hello! Connection successfully made.');  }); Now if there is any data being sent by client, we can capture that data on the server by subscribing to ‘data’ event on the client socket object.  socket.on('data', (data) => {    console.log(data.toString());// since data is streamed in bytes, toString is used.  }); Some of the most commonly used events on ‘net.Socket’ are data, error and close. As the names suggest, data is for listening to any data sent, error when there is an error happens and close event is raised when a connection is closed which happens once. Here is an example in server.js file: const net = require('net');  var server = net.createServer();  server.on("connection", (socket) => {    console.log("new client connection is made", socket.remoteAddress + ":" + socket.remotePort);    socket.on("data", (data) => {      console.log(data.toString());    });    socket.once("close", () => {      console.log("client connection closed.");    });    socket.on("error", (err) => {      console.log("client connection got errored out.")    });    socket.write('SERVER: Hello! Connection successfully made.');  });  server.on('error', (e) => {    if (e.code === 'EADDRINUSE') {      console.log('Address in use, retrying...');      setTimeout(() => {        server.close();        server.listen(PORT, HOST);      }, 1000);    }    else {      console.log("Server failed.")    }  });  server.listen(9000, () => {    console.log('opened server on %j', server.address().port);  }); ‘net’ module also has another class type net.BlockList. This helps in controlling or disabling the inbound or outbound traffic based on rules from any specific IP addresses, IP ranges, or IP subnets. Here is an example snippet from the documentation: const blockList = new net.BlockList();  blockList.addAddress('123.123.123.123');  blockList.addRange('10.0.0.1', '10.0.0.10');  blockList.addSubnet('8592:757c:efae:4e45::', 64, 'ipv6');  console.log(blockList.check('123.123.123.123')); // Prints: true  console.log(blockList.check('10.0.0.3')); // Prints: true  console.log(blockList.check('222.111.111.222')); // Prints: false  // IPv6 notation for IPv4 addresses works:  console.log(blockList.check('::ffff:7b7b:7b7b', 'ipv6')); // Prints: true  console.log(blockList.check('::ffff:123.123.123.123', 'ipv6')); // Prints: true Now that we have the server up and running, we can build a client to connect to the server and start sending bi-directional data. This client could be another node.js application, java/c# application working with TCP sockets, asp.net MVC application talking to node.js TCP server or any other client application. But that client application should have TCP based communication mechanism support. Since we are talking about ‘net’ module, let’s build the client application as well using net module. Moreover, it supports TCP based communication as well. 'net’ module has a factory function called ‘createConnection’ which immediately creates a socket and establishes a connection with the server running on the specified port.  Let's create another client.js file and create a connection. const net = require('net');  const client = net.createConnection({ port: 9000 }, () => {    console.log('CLIENT: I connected to the server.');  }); The first parameter contains the details of the server. Since we are running the server locally, providing the port number would suffice for us as the host default address is localhost for TCP connections. The second parameter is the callback called once the connection is made successfully with the server. The returned value is of type net.Socket which we have learnt about earlier. Let’s hook to ‘data’ event and console log the information sent by the server. client.on('data', (data) => {    console.log(data.toString());    client.end();  }); Here we are not persisting the TCP connection and ending it once we receive a message from the server. We can subscribe to close event and handle any clean up needed. client.on('end', () => {    console.log('CLIENT: I disconnected from the server.');  }) The output on the client terminal has to be:  CLIENT: I connected to the server.  SERVER: Hello! This is server speaking.  CLIENT: I disconnected from the server. Output on server terminal will be: new client connection is made ::ffff:127.0.0.1:51680  CLIENT: Hello this is client!  client connection closed. In case we want to continue the client instance till the server is alive, we can comment out the ‘client.end()’ call. Any message in the terminal can be processed and sent to the server. For reading the text from terminal we use the readline module. Here is a complete example: const net = require('net');  const readline = require('readline');  const rl = readline.createInterface({    input: process.stdin,    output: process.stdout  });  const client = net.createConnection({ port: 9000 }, () => {  console.log('CLIENT: I connected to the server.');    client.write('CLIENT: Hello this is client!');  });  client.on('data', (data) => {    console.log(data.toString());    //client.end();  });  client.on('end', () => {    console.log('CLIENT: I disconnected from the server.');  })  rl.on('line', (input) => {    client.write(`CLIENT: ${input}`);  }); Both client and server now can communicate. When we type any text in client terminal, that is communicated to the server, and the server can respond back to the client via terminal.  ConclusionWebsockets help in creating a full-duplex connection for sending messages from client to server and vice-versa. Some of the real-time use cases that you may be familiar with are chat apps, IoT devices and so on. The Node.js net module helps you to create a server application easily, which can communicate to any type of client application like a web browser, mobile app, IoT device, Node.js client, or anything that knows TCP where the messaging need is bi-directional with streams. ‘net’ module can be used to communicate among child processes within a node.js server as well. 
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Node.Js - Net Module

Node.js has a ‘net’ module which provide... Read More