自定义上下文类型

当内置的上下文类型不满足需求时，可以参照EnvContext的实现，实现自己的上下文类型。

如何实现自定义上下文类型

1. 定义上下文类型

   public class CustomContext
   {
       //上下文会被存储为一个key-value的形式，这个key就是ContextKey
       public static string ContextKey { get; set; } = "x-custom-context"; 
   
       public CustomContext(string data)
       {
           Data = data;
       }
   
       public string Data { get; private set; }
   }
   

2. 实现IContextCarrierHandler接口

   public class CustomContextCarrierHandler : IContextCarrierHandler
   {
       public Type ContextType => typeof(CustomContext);
   
       public void Inject(IContextCarrier carrier, object? context)
       {
           if (context != null)
           {
               carrier.Set(CustomContext.ContextKey, ((CustomContext)context).Data);
           }
       }
   
       public object? Initial()
       {
           return null;
       }
   }
   

3. 实现IContextSourceHandler接口

   public class CustomCContextSourceHandler : IContextSourceHandler
   {
       public Type ContextType => typeof(CustomContext);
   
       public object? Extract(IContextSource source)
       {
           var data = source.Get(CustomContext.ContextKey);
           return string.IsNullOrEmpty(data) ? null : new CustomContext(data);
       }
   }
   

4. 添加注册上下文类型

   public static class ServiceCollectionExtensions
   {
       public static IServiceCollection AddCustomContext(this IServiceCollection services)
       {
           services.AddContextCore();
           services.TryAddSingleton<IContextCarrierHandler, CustomContextCarrierHandler>();
           services.TryAddSingleton<IContextSourceHandler, CustomContextSourceHandler>();
           return services;
       }
   }
   

5. 在Program.cs注册上下文类型

   builder.Services.AddContext()  
       .AddEnvContext()    
       .AddTenantContext() 
       .AddCustomContext()  // 添加自定义上下文
       .AddCapContextProcessor();