Integrating the Modules: Implementing Integration Services
In the previous parts, we created two modules: the Products module to store and manage products and the Orders module to accept orders. However, these modules were completely independent from each other. Only the main application brought them together to execute in the same application, but these modules don't communicate with each other.
In the next three parts, you will learn to implement three patterns for integrating these modules:
- The Order module will make a request to the Products module to get product information when needed.
- The Product module will listen to events from the Orders module, so it can decrease a product's stock count when an order is placed.
- Finally, we will execute a database query that includes product and order data.
Let's begin from the first one: The Integration Services.
The Need for the Integration Services
Remember from the previous part, the Orders page shows products' identities instead of their names:
That is because the Orders module has no access to the product data, so it can not perform a JOIN query to get the names of products from the Products
table. That is a natural result of the modular design. However, we also don't want to show a product's identity on the UI, which is not a good user experience.
As a solution to that problem, the Orders module may ask product names to the Product module using an integration service. Integration service concept in ABP is designed for request/response style inter-module (in modular applications) and inter-microservice (in distributed systems) communication.
When you implement integration services for inter-module communication, you can easily convert them to REST API calls if you convert your solution to a microservice system and convert your modules to services later.
Creating a Products Integration Service
The first step is to create an integration service in the Products module, so other modules can consume it.
We will define an interface in the ModularCrm.Products.Application.Contracts
package and implement it in the ModularCrm.Products.Application
package.
Defining the IProductIntegrationService
Interface
Open the ModularCrm.Products
.NET solution in your IDE, find the ModularCrm.Products.Application.Contracts
project, create an Integration
folder inside inside of that project and finally create an interface named IProductIntegrationService
into that folder. The final folder structure should be like that:
(Creating anIntegration
folder is not required, but it can be a good practice)
Open the IProductIntegrationService.cs
file and replace it's content with the following code block:
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Volo.Abp;
using Volo.Abp.Application.Services;
namespace ModularCrm.Products.Integration
{
[IntegrationService]
public interface IProductIntegrationService : IApplicationService
{
Task<List<ProductDto>> GetProductsByIdsAsync(List<Guid> ids);
}
}
IProductIntegrationService
is very similar to a typical application service. The only difference is that it has an [IntegrationService]
attribute on top of the interface definition. In that way, ABP can recognize and behave differently for them (for example, ABP doesn't expose integration services as HTTP APIs by default if you've configured the Auto API Controllers feature)
IProductIntegrationService
has a single method that gets a list of product Ids and returns a list of ProductDto
objects for these Ids. Any other module can use that method to get details of products when it only has some product Ids. This is exactly what we need in the Ordering module.
Design Tip
You may think if we can use the existing application services (like
IProductAppService
) from other modules instead of creating specific integration services. Technically you can use, ABP has no restriction. However, from good design and best practice points, we don't suggest it. Because, application services are designed to be consumed specifically by the presentation layer. They will have different authorization and validation logic, they will need different DTO input and output properties, they will have different performance, optimization and caching requirements, and so on. And most importantly, all these will change by the time based on UI requirements and these changes may break your integrations later. It is best to implement specific integration APIs that is designed and optimized for that purpose.We've reused the
ProductDto
object created forIProductAppService
, which can be reasonable from a maintenance point of view. But if you think your integration service results will be different from the application service results in the future, it can be good to separate them from the first day so you don't need to introduce breaking changes later.
Implementing the ProductIntegrationService
Class
We've defined the integration service interface. Now, we can implement it in the ModularCrm.Products.Application
project. Create an Integration
folder and then create a ProductIntegrationService
class in that folder. The final folder structure should be like this:
Open the ProductIntegrationService.cs
file and replace its content with the following code block:
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Volo.Abp;
using Volo.Abp.Domain.Repositories;
namespace ModularCrm.Products.Integration
{
[IntegrationService]
public class ProductIntegrationService
: ProductsAppService, IProductIntegrationService
{
private readonly IRepository<Product, Guid> _productRepository;
public ProductIntegrationService(IRepository<Product, Guid> productRepository)
{
_productRepository = productRepository;
}
public async Task<List<ProductDto>> GetProductsByIdsAsync(List<Guid> ids)
{
var products = await _productRepository.GetListAsync(
product => ids.Contains(product.Id)
);
return ObjectMapper.Map<List<Product>, List<ProductDto>>(products);
}
}
}
The implementation is pretty simple. Just using a repository to query Product
entities.
Here, we directly used
List<T>
classes, but instead, you could wrap inputs and outputs into DTOs. In that way, it can be possible to add new properties to these DTOs without changing the signature of your integration service method (and without introducing breaking changes for your client modules).
Consuming the Products Integration Service
The Product Integration Service is ready for the other modules to use. In this section, we will use it in the Ordering module to convert product IDs to product names.
Adding a Reference to the ModularCrm.Products.Application.Contracts
Package
Open the ABP Studio UI and stop the application if it is already running. Then open the Solution Explorer in ABP Studio, right-click the ModularCrm.Ordering
package and select the Add Package Reference command:
In the opening dialog, select the This solution tab, find and check the ModularCrm.Products.Application.Contracts
package and click the OK button:
ABP Studio adds the package reference and arranges the module dependency.
Instead of directly adding such a package reference, it can be best to import the module first (right-click the
ModularCrm.Ordering
module, select the Import Module command and import theModularCrm.Products
module), then install the package reference. In that way, it would be easy to see and keep track of inter-module dependencies.
Using the Products Integration Service
Now, we can inject and use IProductIntegrationService
in the Ordering module codebase.
Open the OrderAppService
class (the OrderAppService.cs
file under the Services
folder of the ModularCrm.Ordering
project of the ModularCrm.Ordering
.NET solution) and change its content as like the following code block:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using ModularCrm.Ordering.Contracts.Enums;
using ModularCrm.Ordering.Contracts.Services;
using ModularCrm.Ordering.Entities;
using ModularCrm.Products.Integration;
using Volo.Abp.Application.Services;
using Volo.Abp.Domain.Repositories;
namespace ModularCrm.Ordering.Services;
public class OrderAppService : ApplicationService, IOrderAppService
{
private readonly IRepository<Order> _orderRepository;
private readonly IProductIntegrationService _productIntegrationService;
public OrderAppService(
IRepository<Order, Guid> orderRepository,
IProductIntegrationService productIntegrationService)
{
_orderRepository = orderRepository;
_productIntegrationService = productIntegrationService;
ObjectMapperContext = typeof(OrderingWebModule);
}
public async Task<List<OrderDto>> GetListAsync()
{
var orders = await _orderRepository.GetListAsync();
// Prepare a list of products we need
var productIds = orders.Select(o => o.ProductId).Distinct().ToList();
var products = (await _productIntegrationService
.GetProductsByIdsAsync(productIds))
.ToDictionary(p => p.Id, p => p.Name);
var orderDtos = ObjectMapper.Map<List<Order>, List<OrderDto>>(orders);
orderDtos.ForEach(orderDto =>
{
orderDto.ProductName = products[orderDto.ProductId];
});
return orderDtos;
}
public async Task CreateAsync(OrderCreationDto input)
{
var order = new Order
{
CustomerName = input.CustomerName,
ProductId = input.ProductId,
State = OrderState.Placed
};
await _orderRepository.InsertAsync(order);
}
}
And also, open the OrderDto
class (the OrderDto.cs
file under the Services
folder of the ModularCrm.Ordering.Contracts
project of the ModularCrm.Ordering
.NET solution) and add a ProductName
property to it:
using System;
using ModularCrm.Ordering.Contracts.Enums;
namespace ModularCrm.Ordering.Contracts.Services;
public class OrderDto
{
public Guid Id { get; set; }
public string CustomerName { get; set; }
public Guid ProductId { get; set; }
public string ProductName { get; set; } // New property
public OrderState State { get; set; }
}
Lastly, open the OrderingApplicationAutoMapperProfile
class (the OrderingApplicationAutoMapperProfile.cs
file under the Services
folder of the ModularCrm.Ordering
project of the ModularCrm.Ordering
.NET solution) and ignore the ProductName
property in the mapping configuration:
using AutoMapper;
using ModularCrm.Ordering.Contracts.Services;
using ModularCrm.Ordering.Entities;
using Volo.Abp.AutoMapper;
namespace ModularCrm.Ordering;
public class OrderingApplicationAutoMapperProfile : Profile
{
public OrderingApplicationAutoMapperProfile()
{
CreateMap<Order, OrderDto>()
.Ignore(x => x.ProductName); // New line
}
}
Let's see what we've changed:
- We've added a
ProductName
property to theOrderDto
class to store the product name. - Injecting the
IProductIntegrationService
interface so we can use it to request products. - In the
GetListAsync
method;- First getting the orders from the ordering module's database just like done before.
- Next, we are preparing a unique list of product IDs since the
GetProductsByIdsAsync
method requests it. - Then we are calling the
IProductIntegrationService.GetProductsByIdsAsync
method to get aList<ProductDto>
object. - In the last line, we are converting the product list to a dictionary, where the key is
Guid Id
and the value isstring Name
. That way, we can easily find a product's name with its ID. - Finally, we are mapping the orders to
OrderDto
objects and setting the product name by looking up the product ID in the dictionary.
Open the Index.cshtml
file, and change the @order.ProductId
part by @Model.ProductName
to write the product name instead of the product ID. The final Index.cshtml
content should be the following:
@page
@model ModularCrm.Ordering.Pages.Orders.IndexModel
<h1>Orders</h1>
<abp-card>
<abp-card-body>
<abp-list-group>
@foreach (var order in Model.Orders)
{
<abp-list-group-item>
<strong>Customer:</strong> @order.CustomerName <br />
<strong>Product:</strong> @order.ProductName <br />
<strong>State:</strong> @order.State
</abp-list-group-item>
}
</abp-list-group>
</abp-card-body>
</abp-card>
That's all. Now, you can graph build the main application and run it in ABP Studio to see the result:
As you can see, we can see the product names instead of product IDs.
In the way explained in this section, you can easily create integration services for your modules and consume these integration services in any other module.
Design Tip
It is suggested that you keep that type of communication to a minimum and not couple your modules with each other. It can make your solution complicated and may also decrease your system performance. When you need to do it, think about performance and try to make some optimizations. For example, if the Ordering module frequently needs product data, you can use a kind of cache layer, so it doesn't make frequent requests to the Products module. Especially if you consider converting your system to a microservice solution in the future, too many direct integration API calls can be a performance bottleneck.