mirror of https://github.com/abpframework/abp.git
Halil İbrahim Kalkan
4 years ago
3 changed files with 228 additions and 1 deletions
@ -0,0 +1,217 @@ |
|||
# Static C# API Client Proxies |
|||
|
|||
ABP can create C# API client proxy code to call your remote HTTP services (REST APIs). In this way, you don't need to deal with `HttpClient` and other low level details to call remote services and get results. |
|||
|
|||
Static C# proxies automatically handle the following stuff for you; |
|||
|
|||
* Maps C# **method calls** to remote server **HTTP calls** by considering the HTTP method, route, query string parameters, request payload and other details. |
|||
* **Authenticates** the HTTP Client by adding access token to the HTTP header. |
|||
* **Serializes** to and deserialize from JSON. |
|||
* Handles HTTP API **versioning**. |
|||
* Add **correlation id**, current **tenant** id and the current **culture** to the request. |
|||
* Properly **handles the error messages** sent by the server and throws proper exceptions. |
|||
|
|||
This system can be used by any type of .NET client to consume your HTTP APIs. |
|||
|
|||
## Static vs Dynamic Client Proxies |
|||
|
|||
ABP provides **two types** of client proxy generation system. This document explains the **static client proxies**, which generates client-side code in your development time. You can also see the [Dynamic C# API Client Proxies](Dynamic-CSharp-API-Clients.md) documentation to learn how to use proxies generated on runtime. |
|||
|
|||
Development-time (static) client proxy generation has a **performance advantage** since it doesn't need to obtain the HTTP API definition on runtime. However, you should **re-generate** the client proxy code whenever you change your API endpoint definition. On the other hand, dynamic client proxies are generated on runtime and provides an **easier development experience**. |
|||
|
|||
## Service Interface |
|||
|
|||
Your service/controller should implement an interface that is shared between the server and the client. So, first define a service interface in a shared library project, typically in the `Application.Contracts` project if you've created your solution using the startup templates. |
|||
|
|||
Example: |
|||
|
|||
````csharp |
|||
public interface IBookAppService : IApplicationService |
|||
{ |
|||
Task<List<BookDto>> GetListAsync(); |
|||
} |
|||
```` |
|||
|
|||
> Your interface should implement the `IRemoteService` interface to be automatically discovered. Since the `IApplicationService` inherits the `IRemoteService` interface, the `IBookAppService` above satisfies this condition. |
|||
|
|||
Implement this class in your service application. You can use [auto API controller system](Auto-API-Controllers.md) to expose the service as a REST API endpoint. |
|||
|
|||
## Client Proxy Generation |
|||
|
|||
First, add [Volo.Abp.Http.Client](https://www.nuget.org/packages/Volo.Abp.Http.Client) nuget package to your client project: |
|||
|
|||
```` |
|||
Install-Package Volo.Abp.Http.Client |
|||
```` |
|||
|
|||
Then add `AbpHttpClientModule` dependency to your module: |
|||
|
|||
````csharp |
|||
[DependsOn(typeof(AbpHttpClientModule))] //add the dependency |
|||
public class MyClientAppModule : AbpModule |
|||
{ |
|||
} |
|||
```` |
|||
|
|||
Now, it's ready to configure the application for the static client proxy generation. Example: |
|||
|
|||
````csharp |
|||
[DependsOn( |
|||
typeof(AbpHttpClientModule), //used to create client proxies |
|||
typeof(BookStoreApplicationContractsModule) //contains the application service interfaces |
|||
)] |
|||
public class MyClientAppModule : AbpModule |
|||
{ |
|||
public override void ConfigureServices(ServiceConfigurationContext context) |
|||
{ |
|||
// Prepare for static client proxy generation |
|||
context.Services.AddStaticHttpClientProxies( |
|||
typeof(BookStoreApplicationContractsModule).Assembly |
|||
); |
|||
} |
|||
} |
|||
```` |
|||
|
|||
`AddStaticHttpClientProxies` method gets an assembly, finds all service interfaces in the given assembly, and prepares for static client proxy generation. |
|||
|
|||
> The [application startup template](../Startup-Templates/Application.md) comes pre-configured for the **dynamic** client proxy generation, in the `HttpApi.Client` project. If you want to switch to the **static** client proxies, change `context.Services.AddHttpClientProxies` to `context.Services.AddStaticHttpClientProxies` in the module class of your `HttpApi.Client` project. |
|||
|
|||
### Endpoint Configuration |
|||
|
|||
`RemoteServices` section in the `appsettings.json` file is used to get remote service address by default. The simplest configuration is shown below: |
|||
|
|||
```json |
|||
{ |
|||
"RemoteServices": { |
|||
"Default": { |
|||
"BaseUrl": "http://localhost:53929/" |
|||
} |
|||
} |
|||
} |
|||
``` |
|||
|
|||
See the *AbpRemoteServiceOptions* section below for more detailed configuration. |
|||
|
|||
### Code Generation |
|||
|
|||
Server side must be up and running while generating the client proxy code. So, run your application that serves the HTTP APIs on the `BaseUrl` that is configured like explained in the *Endpoint Configuration* section. |
|||
|
|||
Open a command-line terminal in the root folder of your client project (`.csproj`) and type the following command: |
|||
|
|||
````bash |
|||
abp generate-proxy -t csharp -u http://localhost:53929/ |
|||
```` |
|||
|
|||
> If you haven't installed yet, you should install the [ABP CLI](../CLI.md). |
|||
|
|||
This command should generate the following files under the `ClientProxies` folder: |
|||
|
|||
 |
|||
|
|||
`BookClientProxy.Generated.cs` is the actual generated proxy class in this example. `BookClientProxy` is a `partial` class where you can write your custom code (ABP won't override it). `app-generate-proxy.json` contains information about the remote HTTP endpoint, so ABP can properly perform HTTP requests. |
|||
|
|||
> `generate-proxy` command generates proxies for only the APIs you've defined in your application. If you are developing a modular application, you can specify the `-m` (or `--module`) parameter to specify the module you want to generate proxies. See the *generate-proxy* section in the [ABP CLI](../CLI.md) documentation for other options. |
|||
|
|||
## Usage |
|||
|
|||
It's straightforward to use the client proxies. Just inject the service interface in the client application code: |
|||
|
|||
````csharp |
|||
public class MyService : ITransientDependency |
|||
{ |
|||
private readonly IBookAppService _bookService; |
|||
|
|||
public MyService(IBookAppService bookService) |
|||
{ |
|||
_bookService = bookService; |
|||
} |
|||
|
|||
public async Task DoItAsync() |
|||
{ |
|||
var books = await _bookService.GetListAsync(); |
|||
foreach (var book in books) |
|||
{ |
|||
Console.WriteLine($"[BOOK {book.Id}] Name={book.Name}"); |
|||
} |
|||
} |
|||
} |
|||
```` |
|||
|
|||
This sample injects the `IBookAppService` service interface defined above. The static client proxy implementation makes an HTTP call whenever a service method is called by the client. |
|||
|
|||
## Configuration |
|||
|
|||
### AbpRemoteServiceOptions |
|||
|
|||
`AbpRemoteServiceOptions` is automatically set from the `appsettings.json` by default. Alternatively, you can configure it in the `ConfigureServices` method of your [module](../Module-Development-Basics.md) to set or override it. Example: |
|||
|
|||
````csharp |
|||
public override void ConfigureServices(ServiceConfigurationContext context) |
|||
{ |
|||
context.Services.Configure<AbpRemoteServiceOptions>(options => |
|||
{ |
|||
options.RemoteServices.Default = |
|||
new RemoteServiceConfiguration("http://localhost:53929/"); |
|||
}); |
|||
|
|||
//... |
|||
} |
|||
```` |
|||
|
|||
### Multiple Remote Service Endpoints |
|||
|
|||
The examples above have configured the "Default" remote service endpoint. You may have different endpoints for different services (as like in a microservice approach where each microservice has different endpoints). In this case, you can add other endpoints to your configuration file: |
|||
|
|||
````json |
|||
{ |
|||
"RemoteServices": { |
|||
"Default": { |
|||
"BaseUrl": "http://localhost:53929/" |
|||
}, |
|||
"BookStore": { |
|||
"BaseUrl": "http://localhost:48392/" |
|||
} |
|||
} |
|||
} |
|||
```` |
|||
|
|||
`AddStaticHttpClientProxies` method can get an additional parameter for the remote service name. Example: |
|||
|
|||
````csharp |
|||
context.Services.AddStaticHttpClientProxies( |
|||
typeof(BookStoreApplicationContractsModule).Assembly, |
|||
remoteServiceConfigurationName: "BookStore" |
|||
); |
|||
```` |
|||
|
|||
`remoteServiceConfigurationName` parameter matches the service endpoint configured via `AbpRemoteServiceOptions`. If the `BookStore` endpoint is not defined then it fallbacks to the `Default` endpoint. |
|||
|
|||
### Retry/Failure Logic & Polly Integration |
|||
|
|||
If you want to add retry logic for the failing remote HTTP calls for the client proxies, you can configure the `AbpHttpClientBuilderOptions` in the `PreConfigureServices` method of your module class. |
|||
|
|||
**Example: Use the [Polly](https://github.com/App-vNext/Polly) library to re-try 3 times on a failure** |
|||
|
|||
````csharp |
|||
public override void PreConfigureServices(ServiceConfigurationContext context) |
|||
{ |
|||
PreConfigure<AbpHttpClientBuilderOptions>(options => |
|||
{ |
|||
options.ProxyClientBuildActions.Add((remoteServiceName, clientBuilder) => |
|||
{ |
|||
clientBuilder.AddTransientHttpErrorPolicy(policyBuilder => |
|||
policyBuilder.WaitAndRetryAsync( |
|||
3, |
|||
i => TimeSpan.FromSeconds(Math.Pow(2, i)) |
|||
) |
|||
); |
|||
}); |
|||
}); |
|||
} |
|||
```` |
|||
|
|||
This example uses the [Microsoft.Extensions.Http.Polly](https://www.nuget.org/packages/Microsoft.Extensions.Http.Polly) package. You also need to import the `Polly` namespace (`using Polly;`) to be able to use the `WaitAndRetryAsync` method. |
|||
|
|||
## See Also |
|||
|
|||
* [Dynamic C# Client Proxies](Dynamic-CSharp-API-Clients.md) |
|||
|
After Width: | Height: | Size: 7.0 KiB |
Loading…
Reference in new issue