How to get customer access token by id for REST api Magento 2?

Get Customer token for the REST API using customer id in Magento 2 used to call API.

If you have customer id, retrieve the token by the Token factory class of the Integration module.

Instantiate the Magento\Integration\Model\Oauth\TokenFactory in your class constructor method.

<?php
namespace Jesadiya\CustomerToken\Model;

use Magento\Integration\Model\Oauth\TokenFactory as TokenModelFactory;

class Token
{
    /**
     * Token Model
     *
     * @var TokenModelFactory
     */
    private $tokenModelFactory;

    public function __construct(
        TokenModelFactory $tokenModelFactory
    ) {
        $this->tokenModelFactory = $tokenModelFactory;
    }

    /**
     * Retrieve customer token
     *
     * @param int $customerId
     * @return string
     */
     public function createToken(int $customerId)
    {
        $token = $this->tokenModelFactory->create()->createCustomerToken($customerId)->getToken();
        return $token;
    }
}

Call method by required input,

$customerId = 1;
$result = $this->createToken($customerId);

Output:
string