How to Get data from database using Graph Ql in Magento 2

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What is a Graph Ql : –

Graph Ql is a query language and server-side runtime that was created back in 2012-2015 by Facebook.

Magento implements Graph Ql to provide an alternative to REST and SOAP web API for frontend development.

Its major aim is speeding up and boosting the API, their flexibility, and their effectiveness.

difference between REST, SOAP API, and Graph Ql lies in the capability of

Graph Ql to obtain clean-cut results in a single call as it needs only one endpoint

REST, on the other hand, normally requires more than one query-send to multiple endpoints in order to achieve the same results

(and most likely these results won’t be as precise as the ones provided by Graph Ql).

Graph Ql is also attractive as a query language due to its approach towards clients. By giving clients the data control, they

have the opportunity to determine what data should be received in the response.

To begin exploring Graph Ql, set the Graph Ql endpoint by entering

http:///graphql in the URL bar of your IDE or extension.

for get data from database using graph Ql need to follow below steps:-

Step1 – Create schema.graphqls file inside

app\code\Vendor\Extension\etc\

and add below code

type Query {
    student(
            stuEmail: String 
        ): 
    Teststudent @resolver(class:"Bluethinkinc\\CustomRestApi\\Model\\Resolver\\Student")
}

type Teststudent {
    student_id: Int
    stu_name: String
    stu_email: String
    message: String
}

type Query {

student(

stuEmail: String

Teststudent @resolver(class:"Bluethinkinc\\CustomRestApi\\Model\\Resolver\\Student")

}

type Teststudent {

student_id: Int

stu_name: String

stu_email: String

message: String

}

Step2 – Create Student.php file inside

app\code\Vendor\Extension\Model\Resolver\

and add below code

<?php
/**
 * @author Bluethinkinc
 * @copyright Copyright (c) 2021
 * @package Bluethinkinc
 */

namespace Bluethinkinc\CustomRestApi\Model\Resolver;

use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;
use Magento\Framework\Exception\NoSuchEntityException;
use Magento\Framework\Exception\LocalizedException;
use Magento\Framework\GraphQl\Config\Element\Field;
use Magento\Framework\GraphQl\Exception\GraphQlAuthorizationException;
use Magento\Framework\GraphQl\Exception\GraphQlNoSuchEntityException;
use Magento\Framework\GraphQl\Query\Resolver\Value;
use Magento\Framework\GraphQl\Query\Resolver\ValueFactory;
use Magento\Framework\GraphQl\Query\ResolverInterface;
use Bluethinkinc\CustomRestApi\Model\StudentFactory;

/**
 * Students field resolver, used for GraphQL request processing.
 */

class Student implements ResolverInterface
{
    /**
     * @var ValueFactory
     */
    private $valueFactory;

    /**
     * @var studentFactory
     */
    private $studentFactory;

    /**
     * @var \Psr\Log\LoggerInterface
     */
    private $logger;

    /**
     *
     * @param ValueFactory $valueFactory
     * @param studentFactory $studentFactory
     */
    public function __construct(
        ValueFactory $valueFactory,
        StudentFactory $studentFactory,
        \Psr\Log\LoggerInterface $logger
    ) {
        $this->valueFactory = $valueFactory;
        $this->studentFactory = $studentFactory;
        $this->logger = $logger;
    }

    /**
     * @param Field $field
     * @param [type] $context
     * @param ResolveInfo $info
     * @param array|null $value
     * @param array|null $args
     * @return array
     */
    public function resolve(
        Field $field,
        $context,
        ResolveInfo $info,
        array $value = null,
        array $args = null
    ) {
        if (!isset($args["stuEmail"])) {
            throw new GraphQlAuthorizationException(
                __("email for student should be specified")
            );
        }
        try {
            $data = $this->getstudentData($args["stuEmail"]);
            $result = function () use ($data) {
                return !empty($data) ? $data : [];
            };
            return $this->valueFactory->create($result);
        } catch (NoSuchEntityException $exception) {
            throw new GraphQlNoSuchEntityException(
                __($exception->getMessage())
            );
        } catch (LocalizedException $exception) {
            throw new GraphQlNoSuchEntityException(
                __($exception->getMessage())
            );
        }
    }

    /**
     *
     * @param int $context
     * @return array
     * @throws NoSuchEntityException|LocalizedException
     */
    private function getstudentData($studentEmail): array
    {
        try {
            $studentData = [];
            $studentColl = $this->studentFactory
                ->create()
                ->getCollection()
                ->addFieldToFilter("stu_email", ["eq" => $studentEmail]);
            foreach ($studentColl as $student) {
                array_push($studentData, $student->getData());
            }
            return isset($studentData[0]) ? $studentData[0] : [];
        } catch (NoSuchEntityException $e) {
            return [];
        } catch (LocalizedException $e) {
            throw new NoSuchEntityException(__($e->getMessage()));
        }
    }
}

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<?php

/**

* @author Bluethinkinc

* @package Bluethinkinc

namespace Bluethinkinc\CustomRestApi\Model\Resolver;

use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;

use Magento\Framework\Exception\NoSuchEntityException;

use Magento\Framework\Exception\LocalizedException;

use Magento\Framework\GraphQl\Config\Element\Field;

use Magento\Framework\GraphQl\Exception\GraphQlAuthorizationException;

use Magento\Framework\GraphQl\Exception\GraphQlNoSuchEntityException;

use Magento\Framework\GraphQl\Query\Resolver\Value;

use Magento\Framework\GraphQl\Query\Resolver\ValueFactory;

use Magento\Framework\GraphQl\Query\ResolverInterface;

use Bluethinkinc\CustomRestApi\Model\StudentFactory;

/**

* Students field resolver, used for GraphQL request processing.

class Student implements ResolverInterface

{

/**

* @var ValueFactory

private $valueFactory;

/**

* @var studentFactory

private $studentFactory;

/**

* @var \Psr\Log\LoggerInterface

private $logger;

/**

* @param ValueFactory $valueFactory

* @param studentFactory $studentFactory

public function __construct(

ValueFactory $valueFactory,

StudentFactory $studentFactory,

\Psr\Log\LoggerInterface $logger

) {

$this->valueFactory = $valueFactory;

$this->studentFactory = $studentFactory;

$this->logger = $logger;

}

/**

* @param Field $field

* @param [type] $context

* @param ResolveInfo $info

* @param array|null $value

* @param array|null $args

* @return array

public function resolve(

Field $field,

$context,

ResolveInfo $info,

array $value = null,

array $args = null

) {

if (!isset($args["stuEmail"])) {

throw new GraphQlAuthorizationException(

__("email for student should be specified")

);

}

try {

$data = $this->getstudentData($args["stuEmail"]);

$result = function () use ($data) {

return !empty($data) ? $data : [];

};

return $this->valueFactory->create($result);

} catch (NoSuchEntityException $exception) {

throw new GraphQlNoSuchEntityException(

__($exception->getMessage())

);

} catch (LocalizedException $exception) {

throw new GraphQlNoSuchEntityException(

__($exception->getMessage())

);

}

/**

* @param int $context

* @return array

* @throws NoSuchEntityException|LocalizedException

private function getstudentData($studentEmail): array

{

try {

$studentData = [];

$studentColl = $this->studentFactory

->create()

->getCollection()

->addFieldToFilter("stu_email", ["eq" => $studentEmail]);

foreach ($studentColl as $student) {

array_push($studentData, $student->getData());

}

return isset($studentData[0]) ? $studentData[0] : [];

} catch (NoSuchEntityException $e) {

return [];

} catch (LocalizedException $e) {

throw new NoSuchEntityException(__($e->getMessage()));

}

Now, Test in Postman

Query - 
{
    student(stuEmail: "admin@gmail.com") {
    student_id
    stu_email
    stu_name
    message
    } 
}
End Points - http://<magento2-server>/graphql