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## Resource: Introduction

## Article: Introduction

## Article Link: https://dev.wix.com/docs/api-reference/business-solutions/e-commerce/extensions/validations/validations-integration-service-plugin/introduction.md

## Article Content:

# About the Wix eCommerce Validations Service Plugin

<blockquote class="important">

__Important:__ 
When developing websites or building apps with Blocks, use [Velo service plugins](https://dev.wix.com/docs/velo/events-service-plugins/about-events-service-plugins-and-the-sdk.md).

</blockquote>

As a validations provider, you can integrate with Wix to allow Wix users to validate a site visitor's cart and checkout. For example, you can validate a specific line item’s quantity if the quantity per order is limited. Wix users can either write their own custom validation logic, or integrate with a 3rd-party validations provider.

The integration is done via an app in the Wix App Market and by implementing the Validations [service plugin](https://dev.wix.com/docs/build-apps/develop-your-app/extensions/backend-extensions/service-plugins/about-service-plugin-extensions.md). After the app is installed on a site, Wix triggers a call to your service whenever the site needs to validate a cart or checkout. If there aren't any validation violations, the method should return an object containing an empty array.



Using the service plugin, you can design your app to validate a cart and checkout for your merchant's customers, including:

+ Minimum cart value.
+ Age of a customer before they proceed to checkout.
+ Line item quantity limit.
+ Valid coupon code.
+ Specific items to ship only to specific regions.
+ Restrict purchases to site members only.
+ Close the checkout on certain days.

## Before you begin

By default, the Validations service plugin only validates a site visitor's checkout. If you want to also validate a site visitor's cart, set the `validateInCart` parameter to `true` in the service plugin's configuration.

## Use Cases

Using the service plugin, you can design your app to validate a cart and checkout for your merchant's customers, including:
+ Minimum cart value.
+ Age of a customer before they proceed to checkout.
+ [Line item quantity limit](https://dev.wix.com/docs/api-reference/business-solutions/e-commerce/extensions/validations/validations-integration-service-plugin/sample-flow.md#wix-ecommerce_validations-integration-spi_sample-flow_validate-a-line-item's-quantity).
+ [Valid coupon code](https://dev.wix.com/docs/api-reference/business-solutions/e-commerce/extensions/validations/validations-integration-service-plugin/sample-flow.md#wix-ecommerce_validations-integration-spi_sample-flow_validate-a-coupon-code-for-a-wix-checkout).
+ Specific items to ship only to specific regions.
+ Restrict purchases to site members only.
+ Close the checkout on certain days. 


::::tabs
:::REST_TAB

## Get started

To enable Wix to communicate with your app:
1. Go to [Extensions](https://dev.wix.com/docs/build-apps/develop-your-app/extensions/about-extensions.md) in your app's dashboard.
1. Click **Create Extension** in the top right.
1. Filter by **eCommerce** in the left menu, then find **Ecom Validations** and click **Create**.
1. Provide the following configuration:

| Name | Type | Description                                                                                                                                                                                                                                                                  |
| --- | --- |------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `deploymentUri`|string| Required. Base URI where the endpoints are called. Wix appends the endpoint path to the base URI. For example, to call the Get Validation Violations endpoint at `https://my-validations.com/v1/get-violations`, the base URI you provide here is `https://my-validations.com`. |
| `componentName`|string| A unique name for this component. This is an internal name that will only appear in the app dashboard.                                                                                                                                                                          |
| `validateInCart`|boolean| Whether to validate the cart page in addition to the checkout page. Default: `false`                                                                                                                                                                                         |

:::
:::SDK_TAB

## Get started

Follow these steps to begin implementing your service plugin.

### Step 1 | Choose a framework

You can implement this service plugin with the following [frameworks](https://dev.wix.com/docs/build-apps/get-started/overview/wix-s-development-frameworks.md):

+ **Wix CLI:** Learn how to [implement a service plugin with the CLI and the SDK](https://dev.wix.com/docs/build-apps/develop-your-app/frameworks/wix-cli/supported-extensions/backend-extensions/service-plugins/add-service-plugin-extensions-with-the-cli.md).
+ **Self-hosted:** Learn how to [implement a self-hosted service plugin with the SDK and the Wix Dev Center](https://dev.wix.com/docs/build-apps/develop-your-app/frameworks/self-hosting/supported-extensions/backend-extensions/add-self-hosted-service-plugin-extensions-with-the-sdk.md).

### Step 2 | Configure your service plugin

To configure and customize your plugin, you need to provide important information in the service plugin configuration file. You can [configure your plugin in the Wix Dev Center](https://dev.wix.com/docs/build-apps/develop-your-app/frameworks/self-hosting/supported-extensions/backend-extensions/add-self-hosted-service-plugin-extensions-with-the-sdk.md#step-1--add-a-service-plugin-extension-to-your-app). For details, see [Validations Extension Configuration](https://dev.wix.com/docs/rest/business-solutions/e-commerce/extensions/validations/validations-integration-service-plugin/extension-config.md).

### Step 3 | Define handler functions

Use [`validations.provideHandlers()`](https://dev.wix.com/docs/build-apps/develop-your-app/frameworks/self-hosting/supported-extensions/backend-extensions/add-self-hosted-service-plugin-extensions-with-the-sdk.md#step-4--define-handler-functions) to define the following handler functions that implement your custom business logic. Make sure you define all required functions.

| Function                    | Required       |
|-----------------------------|----------------|
| [`getValidationViolations()`](https://dev.wix.com/docs/rest/business-solutions/e-commerce/extensions/validations/validations-integration-service-plugin/get-validation-violations.md)    | Yes            |

## Code examples

Below is an example for implementing the Validations service plugin in your code.

### CLI: Basic code structure

This is the basic code structure for implementing the Validations service plugin with the Wix CLI:

```js
import { validations } from '@wix/ecom/service-plugins'

validations.provideHandlers({
  getValidationViolations: async (payload) => {

    const {request, metadata} = payload;

    // Add your logic here

  }
});
  
```

### Self-hosted: Basic code structure

This is the basic code structure for implementing a self-hosted Validations service plugin:

```js
import { createClient } from '@wix/sdk';
import { validations } from '@wix/ecom/service-plugins'

const wixClient = createClient({
  auth: {
    appId: <YOUR_APP_ID>,
    publicKey: <YOUR_APP_PUBLIC_KEY>
  },
  modules: { validations }
});

wixClient.validations.provideHandlers({
  getValidationViolations: async (payload) => {

    const { request, metadata } = payload;

    // Add your logic here

  }
});

// Implement a router to process all requests
express.post('/plugins-and-webhooks/*', (req, res) => {
  wixClient.process(req);
});
  
```

:::
::::


## Terminology

- **Merchant:** Business that offers products on their Wix site to customers.  
- **Severity:** How severe the violation is. The violations are shown on the cart and checkout pages. A warning is displayed as yellow, and allows a site visitor to proceed with caution. An error is displayed as red, and doesn't allow a site visitor to proceed with the eCommerce flow. 
- **Subscription option:** A store owner can create [subscriptions](https://support.wix.com/en/article/wix-stores-selling-product-subscriptions) to sell their products on a recurring basis. A line item can be a subscription. 
- **Target:** Target location on a checkout or cart page where the violation will be displayed. The target violation can either be in a particular `lineItem`, or in an `other` area of the cart or checkout page. 
- **Validation service provider:** A 3rd-party app that implements custom logic to validate the site's cart or checkout.
- **Violations:** A list of any validation violations in a site visitor's cart or checkout. 


## See also

+ [About Service Plugin Extensions](https://dev.wix.com/docs/build-apps/develop-your-app/extensions/backend-extensions/service-plugins/about-service-plugin-extensions.md)
+ [Add a Service Plugin Extension With the CLI](https://dev.wix.com/docs/build-apps/develop-your-app/frameworks/wix-cli/supported-extensions/backend-extensions/service-plugins/add-service-plugin-extensions-with-the-cli.md)
+ [Add a Self-hosted Service Plugin With the SDK](https://dev.wix.com/docs/build-apps/develop-your-app/frameworks/self-hosting/supported-extensions/backend-extensions/add-self-hosted-service-plugin-extensions-with-the-sdk.md)
+ [Add Self-hosted Service Plugin Extensions with REST](https://dev.wix.com/docs/build-apps/develop-your-app/frameworks/self-hosting/supported-extensions/backend-extensions/add-self-hosted-service-plugin-extensions-with-rest.md)