5 .net core 基于工厂的中间件激活

偏执的太偏执、 2023-03-01 11:57 0阅读 0赞

基于工厂的中间件需要继承IMiddleware接口，在请求到来时，会从IMiddlewareFactory中获取中间件实例  
如果中间件没有继承IMiddleware接口，则不会从IMiddlewareFactory中获取  
.netcore具有IMiddlewareFactory的默认实现

## IMiddleware ##

使用基于工厂的中间件（继承IMiddleware接口）：

public class FactoryActivatedMiddleware : IMiddleware
    { 
        private readonly AppDbContext _db;
    
        public FactoryActivatedMiddleware(AppDbContext db)
        { 
            _db = db;
    	}
    
        public async Task InvokeAsync(HttpContext context, RequestDelegate next)
        { 
            var keyValue = context.Request.Query["key"];
    
            if (!string.IsNullOrWhiteSpace(keyValue))
            { 
                _db.Add(new Request()
                    { 
                        DT = DateTime.UtcNow, 
                        MiddlewareActivation = "FactoryActivatedMiddleware", 
                        Value = keyValue
                    });
    
                await _db.SaveChangesAsync();
            }
    
            await next(context);
        }
    }

## 为中间件创建扩展 ##

public static class MiddlewareExtensions
    { 
        public static IApplicationBuilder UseFactoryActivatedMiddleware(
            this IApplicationBuilder builder)
        { 
            return builder.UseMiddleware<FactoryActivatedMiddleware>();
        }
    }

## 将工厂中间件添加内置容器中 ##

public void ConfigureServices(IServiceCollection services)
    { 
        ...
        services.AddTransient<FactoryActivatedMiddleware>();
    }

## 应用中间件 ##

public void Configure (IApplicationBuilder app, IHostingEnvironment env) { 
        ...
        app.UseConventionalMiddleware ();
        ...

## IMiddlewareFactory ##

IMiddlewareFactory 作为域服务注册在容器中