Magento Read data from reviews table and display the json

To retrieve the review collection you can use \Magento\Review\Model\ResourceModel\Review\Product\Collection as unfortunately, as of now, Magento 2 does not provide a service layer for the Review module.

You can inject this class in your constructor:

protected $_productsFactory; public function __construct( ... \Magento\Review\Model\ResourceModel\Review\Product\CollectionFactory $productsFactory, ... ) { ... $this->_productsFactory = $productsFactory; ... } 

Then you can call the following to get the collection:

$collection = $this->_productsFactory->create(); 

If you only want data for one product you can add:

$collection->addEntityFilter($productId); 

Now to encode in JSON you need to inject the \Magento\Framework\Json\Helper\Data class in your constructor:

protected $_productsFactory; protected $_jsonHelper; public function __construct( ... \Magento\Review\Model\ResourceModel\Review\Product\CollectionFactory $productsFactory, \Magento\Framework\Json\Helper\Data $jsonHelper, ... ) { ... $this->_productsFactory = $productsFactory; $this->_jsonHelper = $jsonHelper; ... } 

Now in order to return a proper JSON I suggest you generate an array from the collection based on the data you need:

$result = []; foreach ($collection as $review) { $result[] = ['title' => $review->getTitle(), 'nickname' => $review->getNickname(), 'detail' => $review->getDetail()]; } $this->jsonHelper->jsonEncode($result);