Unleashing Flexibility: Implementing Polymorphic Request Bodies in ASP.NET Core Web API with Swagger UI
In the world of RESTful APIs, you often encounter scenarios where you need to accept different types of data for the same endpoint. This is where polymorphic request bodies come into play, offering a flexible approach to handling diverse input formats.
Let's explore how to implement this powerful feature in ASP.NET Core Web API, enhanced with Swagger UI for a seamless developer experience.
The Problem: Handling Diverse Data
Imagine building an API for a store where you want to accept both product and order information through a single endpoint. Products and orders have distinct properties, and you need a mechanism to differentiate and process them correctly.
Scenario:
Let's say you have the following models:
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
}
public class Order
{
public int Id { get; set; }
public string CustomerName { get; set; }
public List<OrderItem> Items { get; set; }
}
public class OrderItem
{
public int ProductId { get; set; }
public int Quantity { get; set; }
}
Initial Approach (Without Polymorphism):
You might be tempted to create separate endpoints for products and orders:
[HttpPost("products")]
public async Task<IActionResult> CreateProduct([FromBody] Product product)
{
// ... process product creation
}
[HttpPost("orders")]
public async Task<IActionResult> CreateOrder([FromBody] Order order)
{
// ... process order creation
}
While this works, it can lead to redundant code and a less maintainable API. This is where polymorphic request bodies step in.
Implementing Polymorphism
1. Define a Base Class:
Start by defining a base class that represents the common attributes shared by products and orders (or any other type of data you want to support):
public abstract class DataObject
{
public int Id { get; set; }
}
2. Inherit from the Base Class:
Make Product and Order inherit from the DataObject class:
public class Product : DataObject
{
// ... properties specific to Product
}
public class Order : DataObject
{
// ... properties specific to Order
}
3. Use [FromBody] with Type Parameter:
In your controller, use the [FromBody] attribute with the Type parameter to indicate the expected type:
[HttpPost("data")]
public async Task<IActionResult> CreateData([FromBody] DataObject data)
{
if (data is Product product)
{
// Process product creation
}
else if (data is Order order)
{
// Process order creation
}
else
{
return BadRequest("Invalid data type");
}
return Ok();
}
4. Leverage Swagger UI for Clarity:
To make your API intuitive for developers, integrate Swagger UI. Swagger UI automatically generates documentation based on your API endpoints, making it easy to understand how to interact with them.
5. Configure Swagger UI:
Add the following NuGet packages to your project:
- Swashbuckle.AspNetCore
- Swashbuckle.AspNetCore.SwaggerUI
Then, in your Startup.cs, configure Swagger UI:
public void ConfigureServices(IServiceCollection services)
{
services.AddSwaggerGen(c =>
{
c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
// ... other Swagger configuration
});
}
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
app.UseSwagger();
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API v1");
// ... other Swagger UI configuration
});
}
Insights and Benefits:
- Reduced Redundancy: Polymorphism allows you to process different data types using a single endpoint, eliminating the need for separate actions for each type.
- Improved Maintainability: This approach simplifies your API structure, making it easier to manage and evolve over time.
- Enhanced Flexibility: Your API can easily adapt to new data types without requiring significant changes to the existing code.
- Clear Documentation with Swagger UI: Swagger UI provides intuitive documentation, allowing developers to understand the API's behavior and how to interact with it, including the different data types that can be submitted.
Example:
Let's see how this works in practice. You can send a JSON payload like this to your API endpoint:
{
"Id": 1,
"Name": "Laptop",
"Price": 1200
}
This payload will be recognized as a Product object, and the code will process it accordingly.
Conclusion:
Polymorphic request bodies provide a flexible and efficient solution for handling diverse data types in ASP.NET Core Web API. Combined with Swagger UI, you gain a powerful tool for building maintainable and developer-friendly APIs. This technique allows you to create APIs that are adaptable to changing requirements, paving the way for future scalability and growth.
