How do I post JSON to a web API method?

Question

I want to send a JSON string via API, and then parse the JSON in code. I don't want Magento to try to convert my JSON parameter to a PHP object.

I'm trying to add this to the stock registry API. Here's the code that I've added.

webapi.xml

<route url="/V1/products/stockItems/update/" method="POST">
    <service class="Magento\CatalogInventory\Api\StockRegistryInterface" method="updateStockItems"/>
    <resources>
        <resource ref="Magento_CatalogInventory::cataloginventory"/>
    </resources>
</route>

StockRegistryInterface.php

public function updateStockItems($stockItems);

StockRegistry.php

public function updateStockItems($stockItems)
{
   // do stuff
}

I'm posting to http://magento.test/rest/V1/products/stockItems/update using Postman.

Here is my request address and headers.

Here's my JSON body

{
   "stockItems": [
      {
        "item_id": 1,
        "product_id": 1,
        "stock_id": 1,
        "qty": 15
      },
      {
        "item_id": 2,
        "product_id": 2,
        "stock_id": 2,
        "qty": 15
      }
   ]
}

I'm getting the error

[2019-03-06 18:22:44] main.CRITICAL: Report ID: webapi-5c800ff4b4623;
Message: Class  does not exist {"exception":"[object] (Exception(code: -1):
Report ID: webapi-5c800ff4b4623; Message: Class  does not exist at 
/var/www/magento2/lib/internal/Magento/Framework/Webapi/
ErrorProcessor.php:205, ReflectionException(code: -1): 
Class  does not exist at /var/www/magento2/lib/internal/Magento/Framework/
Webapi/ServiceInputProcessor.php:162)"} []

How do I get Magento to let me pass my JSON into updateStockItems without trying to convert it to a Magento object?

Update

I can get it to work by passing my JSON as a string and then parsing that string into JSON in the PHP code. If I use the following as the body of my request, it works. But that seems like a dirty workaround. Is there a better way of doing it?

{ "stockItems": "[ {\"sku\": \"SKU-1234\", \"quantity\": 1234}, {\"sku\": \"SKU-5678\", \"quantity\": 5678} ]" }

And here's my PHP code (getStockItemBySku is an existing Magento function within StockRegistry.php)

public function updateStockItems($stockItems)
{
    $json = json_decode($stockItems, true);
    $updatedItemCount = 0;
    foreach ($json as $productJson)
    {            
        $sku = $productJson['sku'];
        $quantity = $productJson['quantity'];
        if ($sku !== NULL && $quantity != NULL)
        {
            $stockItem = $this->getStockItemBySku($sku);
            if ($stockItem !== NULL)
            {
                $stockItem->setQty($quantity);
                $this->stockItemRepository->save($stockItem);
                $updatedItemCount++;
            }
        }
    }
    return $updatedItemCount;
}

Answer 1

I hope you don't have the intention to "hack" Magento core files. I recommend to create your own classes / interfaces for that!

Anyway if you are implementing a custom method updateStockItems for a webapi which updates more stockitems with a single request you should take care of the right method signature: You are expecting an array of stock items, therefore your input parameter should be of that type.

Your interface:

/**
 * 
 * @param \Magento\CatalogInventory\Api\Data\StockItemInterface[] $stockItems
 * @return int
 * @throws \Magento\Framework\Exception\NoSuchEntityException
 */
public function updateStockItems(\Magento\CatalogInventory\Api\Data\StockItemInterface[] $stockItems);

Your method implementation:

/**
 * 
 * @param \Magento\CatalogInventory\Api\Data\StockItemInterface[] $stockItems
 * @return int
 * @throws \Magento\Framework\Exception\NoSuchEntityException
 */
public function updateStockItems(\Magento\CatalogInventory\Api\Data\StockItemInterface[] $stockItems)
{
    foreach ($stockItems as $stockItem){
        //do whatever with your stock item
    }
};

Please take care to use only parameter in your JSON objects which match the used interfaces, in this example \Magento\CatalogInventory\Api\Data\StockItemInterface. So putting there some key sku doesn't make sense and should either be ignored by Magento or give you an error in the API call.

Here is the documentation about the usage of custom webservices.

https://devdocs.magento.com/guides/v2.3/extension-dev-guide/service-contracts/service-to-web-service.html

Answer 2

The rest API address you are using seems not correct. Have a look at this page, under the cataloginventory section:

https://devdocs.magento.com/guides/v2.3/rest/list.html#cataloginventory

As you can see the available URLs are different from the one you are using.

The correct one you should be using is this one:

PUT    /V1/products/:productSku/stockItems/:itemId

And you can update one stock at a time, so you need to call the API for each product you want to update.