Guide to Understand GraphQL

GraphQL is a query language for APIs. This tutorial on GraphQL will introduce you to this popularly used query language.

Why GraphQL?

To answer this question, look at the Rest API first. A REST API (also known as a RESTful API) is a programming interface (API or web API) that adheres to the REST architectural style's requirements. APIs expose their functionality as resources in REST architecture, which can be any form of service, data, or object that a client can access. Each resource has its own URI (Uniform Resource Identifier), which a client can get by sending a request to the server. Client applications were relatively straightforward when the REST concept was invented, and development speed was not quite as fast as it is now. As a result, REST was a suitable fit for many applications. However, the API environment has shifted dramatically in recent years. To cater to these changes, GraphQL was introduced. It brought the following to the table - 

• GraphQL reduces the amount of data transmitted over the network, significantly improving apps that operate in these environments.
• Each client can access exactly the data it requires with GraphQL.
• When using REST APIs, the way data is provided by the server must frequently be changed to account for client-side requirements and design changes. Fast development processes and product revisions are hampered as a result of this.

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What Is GraphQL? 

GraphQL is a data querying language. GraphQL, unlike most query languages (such as SQL), is not used to query a specific type of data storage (such as a MySQL database). GraphQL is used instead to query data from a variety of different sources. It was created with the goal of making APIs that are quick, versatile, and developer-friendly. It can even be used within the GraphiQL integrated development environment (IDE). GraphQL, a REST alternative, allows developers to create requests that pull data from various sources in a single API call.

GraphQL allows API administrators to add or remove fields without affecting existing queries. Developers can use many methods to create APIs, and the GraphQL definition will ensure that they work consistently.

Features of GraphQL

Now that you know what GraphQL is, this section will explain its salient features. 

Queries and Mutations

An operation in GraphQL can be either a read or a write. To read or fetch values, a GraphQL query is used, while to write or post values, a mutation is utilized.

Data Source Agnostic

It makes no difference to GraphQL where data originates from. It could come from a database, a micro-service, or even a RESTful API on the backend.

Runtime

GraphQL runs on the server side making it a dynamic and a runtime environment.

Served Over HTTP

GraphQL is usually sent via HTTP. This means that operations are merely strings, and therefore you don't need any extra software to query data from a GraphQL server.

GraphQL Is Fully-Typed

• GraphQL APIs are arranged by the data they deliver, rather than by endpoints.
• From a single endpoint, developers may access all of their data's capabilities.
• Types are used in GraphQL to ensure that apps only ask for what is feasible and that failures are explicit and useful.

Using GraphQL comes with some great benefits. The coming section defines a few.

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Advantages of GraphQL

• In a GraphQL application, a GraphQL schema establishes a single source of truth. It allows an organization to federate all of its APIs.
• Calls to GraphQL are processed in a single round trip. Clients receive exactly what they ask for, with no over-fetching.
• Strongly defined data types help clients and servers communicate more effectively.
• GraphQL is a self-reflective language. A client might ask for a list of the data kinds that are available. This is perfect for creating documentation on the fly.
• With GraphQL, an application's API can grow without affecting previous requests.
• Numerous open-source GraphQL extensions are available that provide functionality not available in REST APIs.
• GraphQL does not require any particular application architecture. It may be added to an existing REST API and is compatible with existing API management tools.

Limitations of GraphQL

• For developers who are used to working with REST APIs, GraphQL has a steep learning curve.
• GraphQL moves a lot of the effort of a data query to the server, which complicates things for server developers.
• GraphQL may require different API management tactics than REST APIs, depending on how it's implemented, especially when it comes to the rate restrictions and pricing.
• Caching is more difficult to implement than REST.
• Maintainers of APIs also have the responsibility of writing maintainable GraphQL schema.

A Simple GraphQL Query

GraphQL is a query language that allows you to ask for specific fields on objects. 

Consider the following query. 

Query

{

  employee {

    name

  }

}

Result

{

  “employee": {

    "name": “John"

  }

}

The query and the result have the same shape. This is critical with GraphQL because you always get what you anticipate, and the server understands exactly which attributes the client is requesting.

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You can also request data by passing arguments. 

Request

{

  emp(id: "1000") {

    name

    location

  }

}

Result

{

  "data": {

    "emp": {

      "name": "Dorothy,

      "location": "Kansas"

    }

  }

}

The data returned is specific to the employee ID passed as a parameter. 

This was a simple example to demonstrate how a GraphQL query works. 

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Next Steps

Hope that this tutorial on ‘What is GraphQL’ helped you get a basic understanding of GraphQL and why it’s being widely adopted. 

If you wish to learn more about such backend Query Languages and frameworks, check out the Simplilearn's Post Graduate Program in Full Stack Web Development and Full Stack Web Developer - MEAN Stack course and enroll for the course that suits your requirements.

Do you have any questions that you'd want to ask us? Leave a comment in the comments box if you have any suggestions or queries. Our professionals will respond as quickly as possible!