> For the complete documentation index, see [llms.txt](https://doc.ecomm.api.tietoevry.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.ecomm.api.tietoevry.com/integrations/unified-merchant-api-sdk.md).

# Unified Merchant API SDK

The Unified Merchant API SDK provides production-ready server-side SDKs for integrating merchant backend applications with the Payment Gateway.

Available for Java, .NET, and PHP, the SDK abstracts authentication, encryption, API communication, and webhook handling, allowing developers to focus on business logic instead of payment infrastructure.

Whether you’re building a custom e-commerce platform, integrating into an ERP system, or extending an existing checkout, the SDK provides a consistent and secure integration model across supported languages.

## Benefits

The Unified Merchant API SDK simplifies backend payment integration by providing reusable libraries that standardize communication with the Payment Gateway.

#### Multi-language Support

Use the SDK in your preferred backend technology while maintaining a consistent integration model.

Supported platforms include:

* Java
* .NET
* PHP

#### Faster Integration

Reduce development effort with pre-built components for authentication, API communication, encryption, and payment notifications.

#### Secure by Design

Security capabilities are built into the SDK, reducing implementation complexity while supporting secure payment processing.

#### Production Ready

The SDK includes robust error handling, typed request models, and reusable components suitable for enterprise payment integrations.

## Core Capabilities

### Authentication

Secure access to the Payment Gateway using OAuth 2.0.

Features include:

* Automatic access token management
* Client credential authentication
* Secure connection to Sandbox and Production environments

### Secure Encryption

Sensitive payment information is encrypted before transmission to the Payment Gateway.

Capabilities include:

* Client-side JWE encryption
* Secure payload handling
* Automatic encryption key management

### Gateway API Client

The SDK provides strongly typed client libraries for interacting with the Payment Gateway.

Supported operations include:

* Merchant services
* Payment initiation
* Payment status retrieval
* Checkout sessions
* Token management
* Payment operations

### Webhook Support

Receive asynchronous notifications from the Payment Gateway to keep backend systems synchronized with payment events.

Typical notifications include:

* Payment completed
* Payment failed
* Payment cancelled
* Refund processed
* Status updates

### Reusable Models

The SDK includes typed request and response models that reduce development effort and improve code quality.

Benefits include:

* Builder-based request objects
* Strong typing
* Built-in validation
* Consistent API structure

### Developer Productivity

Designed to accelerate development through reusable components and simplified APIs.

The SDK provides:

* Fluent APIs
* Standardized error handling
* Built-in serialization
* Configurable logging
* Extensible architecture

## Typical Integration Flow

```
Merchant Backend
(Java | .NET | PHP)
        │
        ▼
Unified Merchant API SDK
        │
        ├── Authentication
        ├── Encryption
        ├── Request Validation
        ├── API Communication
        └── Webhook Processing
                │
                ▼
Payment Gateway
                │
                ▼
Payment Networks / Acquirers
                │
                ▼
Payment Result
                │
                ▼
Merchant Backend
```

## Deployment Role

The Unified Merchant API SDK acts as the integration layer between the merchant’s backend application and the Payment Gateway.

The merchant backend remains responsible for:

* Order management
* Customer management
* Checkout orchestration
* Business rules
* Inventory management
* Post-payment processing

The SDK is responsible for:

* Secure gateway connectivity
* Authentication
* Request encryption
* API communication
* Webhook processing
* Error handling

## When to Use the Unified Merchant API SDK

The SDK is recommended for merchants who need:

* Custom e-commerce integrations
* Backend payment processing
* Secure server-to-server communication
* Multi-language development support
* Simplified gateway integration
* Enterprise-grade payment services


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