路由是通过UseRouting和UseEndpoints两个中间件配合在一起来完成注册的:
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
// 添加Routing相关服务
// 注意,其已在 ConfigureWebDefaults 中添加,无需手动添加,此处仅为演示
services.AddRouting();
}
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
app.UseRouting();
app.UseEndpoints(endpoints =>
{
endpoints.MapGet("/", async context =>
{
await context.Response.WriteAsync("Hello World!");
});
});
}
}
UseRouting与UseEndpoints必须同时使用,而且必须先调用UseRouting,再调用UseEndpoints
先了解一下终结点的类结构:
public class Endpoint
{
public Endpoint(RequestDelegate requestDelegate, EndpointMetadataCollection? metadata, string? displayName);
public string? DisplayName { get; }
public EndpointMetadataCollection Metadata { get; }
public RequestDelegate RequestDelegate { get; }
public override string? ToString();
}
终结点有以下特点:
在中间件管道中,我们可以通过HttpContext来检索终结点等信息。需要注意的是,终结点对象在创建完毕后,是不可变的,无法修改。
我们一起看下面的代码:
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
app.Use(next => context =>
{
// 在 UseRouting 调用前,始终为 null
Console.WriteLine($"1. Endpoint: {context.GetEndpoint()?.DisplayName ?? "null"}");
return next(context);
});
// EndpointRoutingMiddleware 调用 SetEndpoint 来设置终结点
app.UseRouting();
app.Use(next => context =>
{
// 如果路由匹配到了终结点,那么此处就不为 null,否则,还是 null
Console.WriteLine($"2. Endpoint: {context.GetEndpoint()?.DisplayName ?? "null"}");
return next(context);
});
// EndpointMiddleware 通过 GetEndpoint 方法获取终结点,
// 然后执行该终结点的 RequestDelegate 委托
app.UseEndpoints(endpoints =>
{
endpoints.MapGet("/", context =>
{
// 匹配到了终结点,肯定不是 null
Console.WriteLine($"3. Endpoint: {context.GetEndpoint()?.DisplayName ?? "null"}");
return Task.CompletedTask;
}).WithDisplayName("Custom Display Name"); // 自定义终结点名称
});
app.Use(next => context =>
{
// 只有当路由没有匹配到终结点时,才会执行这里
Console.WriteLine($"4. Endpoint: {context.GetEndpoint()?.DisplayName ?? "null"}");
return next(context);
});
}
当访问/时,输出为:
1. Endpoint: null
2. Endpoint: Custom Display Name
3. Endpoint: Custom Display Name
当访问其他不匹配的URL时,输出为:
1. Endpoint: null
2. Endpoint: null
4. Endpoint: null
当路由匹配到了终结点时,EndpointMiddleware则是该路由的终端中间件;当未匹配到终结点时,会继续执行后面的中间件。
终端中间件:与普通中间件不同的是,该中间件执行后即返回,不会调用后面的中间件。
可以通过以下方法将委托关联到终结点
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
app.UseRouting();
// 在执行终结点前进行授权
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapGet("/", async context => await context.Response.WriteAsync("get"));
endpoints.MapPost("/", async context => await context.Response.WriteAsync("post"));
endpoints.MapPut("/", async context => await context.Response.WriteAsync("put"));
endpoints.MapDelete("/", async context => await context.Response.WriteAsync("delete"));
endpoints.MapHealthChecks("/healthChecks");
endpoints.MapControllers();
});
}
规则:
路由模板中的星号和双星号**被称为catch-all参数,该参数可以作为路由参数的前缀,如/Book/{id}、/Book/{**id},可以匹配以/Book开头的任意Url,如/Book、/Book/、/Book/abc、/Book/abc/def等。
和**在一般使用上没有什么区别,它们仅仅在使用LinkGenerator时会有不同,如id = abc/def,当使用/Book/{id}模板时,会生成/Book/abc%2Fdef,当使用/Book/{**id}模板时,会生成/Book/abc/def。
复杂段通过非贪婪的方式从右到左进行匹配,例如[Route(“/a{b}c{d}”)]就是一个复杂段。实际上,它的确很复杂,只有了解它的工作方式,才能正确的使用它。
接下来,就拿模板[Route(“/a{b}c{d}”)]来举两个例子:
成功匹配的案例——当Url为/abcd时,匹配过程为(|用于辅助展示算法的解析方式):
匹配失败的案例——当Url为/aabcd时,匹配过程为(|用于辅助展示算法的解析方式):
使用复杂段,相比普通路由模板来说,会造成更加昂贵的性能影响
通过路由约束,可以在路由匹配过程中,检查URL是否是可接受的。另外,路由约束一般是用来消除路由歧义,而不是用来进行输入验证的。
实现上,当Http请求到达时,路由参数和该参数的约束名会传递给IInlineConstraintResolver服务,IInlineConstraintResolver服务会负责创建IRouteConstraint实例,以针对Url进行处理。
约束 | 示例 | 匹配项示例 | 说明 |
---|---|---|---|
int | {id:int} | 123456789, -123456789 | 匹配任何整数 |
bool | {active:bool} | true, FALSE | 匹配 true 或 false。 不区分大小写 |
datetime | {dob:datetime} | 2016-12-31, 2016-12-31 7:32pm | 匹配固定区域中的有效 DateTime 值 |
decimal | {price:decimal | 49.99, -1,000.01 | 匹配固定区域中的有效 decimal 值。 |
double | {weight:double} | 1.234, -1,001.01e8 | 匹配固定区域中的有效 double 值。 |
float | {weight:float} | 1.234, -1,001.01e8 | 匹配固定区域中的有效 float 值。 |
guid | {id:guid} | CD2C1638-1638-72D5-1638-DEADBEEF1638 | 匹配有效的 Guid 值 |
long | {ticks:long} | 123456789, -123456789 | 匹配有效的 long 值 |
minlength(value) | {username:minlength(4)} | Rick | 字符串必须至少为 4 个字符 |
maxlength(value) | {filename:maxlength(8)} | MyFile | 字符串不得超过 8 个字符 |
length(length) | {filename:length(12)} | somefile.txt | 字符串必须正好为 12 个字符 |
length(min,max) | {filename:length(8,16)} | somefile.txt | 字符串必须至少为 8 个字符,且不得超过 16 个字符 |
min(value) | {age:min(18)} | 19 | 整数值必须至少为 18 |
max(value) | {age:max(120)} | 91 | 整数值不得超过 120 |
range(min,max) | {age:range(18,120)} | 91 | 整数值必须至少为 18,且不得超过 120 |
alpha | {name:alpha} | Rick | 字符串必须由一个或多个字母字符组成,a-z,并区分大小写。 |
regex(expression) | {ssn:regex(^\d{{3}}-\d{{2}}-\d{{4}}$)} | 123-45-6789 | 字符串必须与正则表达式匹配 |
required | {name:required} | Rick | 用于强制在 URL 生成过程中存在非参数值 |
通过regex(expression)来设置正则表达式约束,并且该正则表达式是:
另外,还需要注意对某些字符进行转义:
例如:
标准正则表达式 | 转义的正则表达式 |
---|---|
^\d{3}-\d{2}-\d{4}$ | ^\d{{3}}-\d{{2}}-\d{{4}}$ |
^[a-z]{2}$ | ^[[a-z]]{{2}}$ |
});
context =>
{
return context.Response.WriteAsync("inline-constraint match");
});
// 变量声明方式
app.UseEndpoints(endpoints =>
{
endpoints.MapControllerRoute(
name: “people”,
pattern: “People/{ssn}”,
constraints: new { ssn = “^\d{3}-\d{2}-\d{4}$”, },
defaults: new { controller = “People”, action = “List”, });
});
> 不要书写过于复杂的正则表达式,否则,相比普通路由模板来说,会造成更加昂贵的性能影响
###### 自定义路由约束
先说一句,自定义路由约束很少会用到,在你决定要自定义路由约束之前,先想想是否有其他更好的替代方案,如使用模型绑定。
通过实现IRouteConstraint接口来创建自定义路由约束,该接口仅有一个Match方法,用于验证路由参数是否满足约束,返回true表示满足约束,false则表示不满足约束。
以下示例要求路由参数中必须包含字符串“1”:
```csharp
public class MyRouteConstraint : IRouteConstraint
{
public bool Match(HttpContext httpContext, IRouter route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection)
{
if (values.TryGetValue(routeKey, out object value))
{
var valueStr = Convert.ToString(value, CultureInfo.InvariantCulture);
return valueStr?.Contains("1") ?? false;
}
return false;
}
}
然后进行路由约束注册:
public void ConfigureServices(IServiceCollection services)
{
services.AddRouting(options =>
{
// 添加自定义路由约束,约束 Key 为 my
options.ConstraintMap["my"] = typeof(MyRouteConstraint);
});
}
最后你就可以类似如下进行使用了:
[HttpGet("{id:my}")]
public string Get(string id)
{
return id;
}
考虑一下,有两个路由模板:/Book/List和/Book/{id},当url为/Book/List时,会选择哪个呢?从结果我们可以得知,是模板/Book/List。它是根据以下规则来确定的:
public static class RoutingServiceCollectionExtensions
{
public static IServiceCollection AddRouting(this IServiceCollection services)
{
// 内联约束解析器,负责创建 IRouteConstraint 实例
services.TryAddTransient<IInlineConstraintResolver, DefaultInlineConstraintResolver>();
// 对象池
services.TryAddTransient<ObjectPoolProvider, DefaultObjectPoolProvider>();
services.TryAddSingleton<ObjectPool<UriBuildingContext>>(s =>
{
var provider = s.GetRequiredService<ObjectPoolProvider>();
return provider.Create<UriBuildingContext>(new UriBuilderContextPooledObjectPolicy());
});
services.TryAdd(ServiceDescriptor.Transient<TreeRouteBuilder>(s =>
{
var loggerFactory = s.GetRequiredService<ILoggerFactory>();
var objectPool = s.GetRequiredService<ObjectPool<UriBuildingContext>>();
var constraintResolver = s.GetRequiredService<IInlineConstraintResolver>();
return new TreeRouteBuilder(loggerFactory, objectPool, constraintResolver);
}));
// 标记已将所有路由服务注册完毕
services.TryAddSingleton(typeof(RoutingMarkerService));
var dataSources = new ObservableCollection<EndpointDataSource>();
services.TryAddEnumerable(ServiceDescriptor.Transient<IConfigureOptions<RouteOptions>, ConfigureRouteOptions>(
serviceProvider => new ConfigureRouteOptions(dataSources)));
// EndpointDataSource,用于全局访问终结点列表
services.TryAddSingleton<EndpointDataSource>(s =>
{
return new CompositeEndpointDataSource(dataSources);
});
services.TryAddSingleton<ParameterPolicyFactory, DefaultParameterPolicyFactory>();
// MatcherFactory,用于根据 EndpointDataSource 创建 Matcher
services.TryAddSingleton<MatcherFactory, DfaMatcherFactory>();
// DfaMatcherBuilder,用于创建 DfaMatcher 实例
services.TryAddTransient<DfaMatcherBuilder>();
services.TryAddSingleton<DfaGraphWriter>();
services.TryAddTransient<DataSourceDependentMatcher.Lifetime>();
services.TryAddSingleton<EndpointMetadataComparer>(services =>
{
return new EndpointMetadataComparer(services);
});
// LinkGenerator相关服务
services.TryAddSingleton<LinkGenerator, DefaultLinkGenerator>();
services.TryAddSingleton<IEndpointAddressScheme<string>, EndpointNameAddressScheme>();
services.TryAddSingleton<IEndpointAddressScheme<RouteValuesAddress>, RouteValuesAddressScheme>();
services.TryAddSingleton<LinkParser, DefaultLinkParser>();
// 终结点选择、匹配策略相关服务
services.TryAddSingleton<EndpointSelector, DefaultEndpointSelector>();
services.TryAddEnumerable(ServiceDescriptor.Singleton<MatcherPolicy, HttpMethodMatcherPolicy>());
services.TryAddEnumerable(ServiceDescriptor.Singleton<MatcherPolicy, HostMatcherPolicy>());
services.TryAddSingleton<TemplateBinderFactory, DefaultTemplateBinderFactory>();
services.TryAddSingleton<RoutePatternTransformer, DefaultRoutePatternTransformer>();
return services;
}
public static IServiceCollection AddRouting(
this IServiceCollection services,
Action<RouteOptions> configureOptions)
{
services.Configure(configureOptions);
services.AddRouting();
return services;
}
}
public static class EndpointRoutingApplicationBuilderExtensions
{
private const string EndpointRouteBuilder = "__EndpointRouteBuilder";
public static IApplicationBuilder UseRouting(this IApplicationBuilder builder)
{
VerifyRoutingServicesAreRegistered(builder);
var endpointRouteBuilder = new DefaultEndpointRouteBuilder(builder);
// 将 endpointRouteBuilder 放入共享字典中
builder.Properties[EndpointRouteBuilder] = endpointRouteBuilder;
// 将 endpointRouteBuilder 作为构造函数参数传入 EndpointRoutingMiddleware
return builder.UseMiddleware<EndpointRoutingMiddleware>(endpointRouteBuilder);
}
private static void VerifyRoutingServicesAreRegistered(IApplicationBuilder app)
{
// 必须先执行了 AddRouting
if (app.ApplicationServices.GetService(typeof(RoutingMarkerService)) == null)
{
throw new InvalidOperationException(Resources.FormatUnableToFindServices(
nameof(IServiceCollection),
nameof(RoutingServiceCollectionExtensions.AddRouting),
"ConfigureServices(...)"));
}
}
}
终于到了路由匹配的逻辑了,才是我们应该关注的,重点查看Invoke:
internal sealed class EndpointRoutingMiddleware
{
private const string DiagnosticsEndpointMatchedKey = "Microsoft.AspNetCore.Routing.EndpointMatched";
private readonly MatcherFactory _matcherFactory;
private readonly ILogger _logger;
private readonly EndpointDataSource _endpointDataSource;
private readonly DiagnosticListener _diagnosticListener;
private readonly RequestDelegate _next;
private Task<Matcher>? _initializationTask;
public EndpointRoutingMiddleware(
MatcherFactory matcherFactory,
ILogger<EndpointRoutingMiddleware> logger,
IEndpointRouteBuilder endpointRouteBuilder,
DiagnosticListener diagnosticListener,
RequestDelegate next)
{
_matcherFactory = matcherFactory ?? throw new ArgumentNullException(nameof(matcherFactory));
_logger = logger ?? throw new ArgumentNullException(nameof(logger));
_diagnosticListener = diagnosticListener ?? throw new ArgumentNullException(nameof(diagnosticListener));
_next = next ?? throw new ArgumentNullException(nameof(next));
_endpointDataSource = new CompositeEndpointDataSource(endpointRouteBuilder.DataSources);
}
public Task Invoke(HttpContext httpContext)
{
// 已经选择了终结点,则跳过匹配
var endpoint = httpContext.GetEndpoint();
if (endpoint != null)
{
Log.MatchSkipped(_logger, endpoint);
return _next(httpContext);
}
// 等待 _initializationTask 初始化完成,进行匹配,并流转到下一个中间件
var matcherTask = InitializeAsync();
if (!matcherTask.IsCompletedSuccessfully)
{
return AwaitMatcher(this, httpContext, matcherTask);
}
// _initializationTask在之前就已经初始化完成了,直接进行匹配任务,并流转到下一个中间件
var matchTask = matcherTask.Result.MatchAsync(httpContext);
if (!matchTask.IsCompletedSuccessfully)
{
return AwaitMatch(this, httpContext, matchTask);
}
// 流转到下一个中间件
return SetRoutingAndContinue(httpContext);
static async Task AwaitMatcher(EndpointRoutingMiddleware middleware, HttpContext httpContext, Task<Matcher> matcherTask)
{
var matcher = await matcherTask;
// 路由匹配,选择终结点
await matcher.MatchAsync(httpContext);
await middleware.SetRoutingAndContinue(httpContext);
}
static async Task AwaitMatch(EndpointRoutingMiddleware middleware, HttpContext httpContext, Task matchTask)
{
await matchTask;
await middleware.SetRoutingAndContinue(httpContext);
}
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private Task SetRoutingAndContinue(HttpContext httpContext)
{
// 终结点仍然为空,则匹配失败
var endpoint = httpContext.GetEndpoint();
if (endpoint == null)
{
Log.MatchFailure(_logger);
}
else
{
// 匹配成功则触发事件
if (_diagnosticListener.IsEnabled() && _diagnosticListener.IsEnabled(DiagnosticsEndpointMatchedKey))
{
// httpContext对象包含了相关信息
_diagnosticListener.Write(DiagnosticsEndpointMatchedKey, httpContext);
}
Log.MatchSuccess(_logger, endpoint);
}
// 流转到下一个中间件
return _next(httpContext);
}
private Task<Matcher> InitializeAsync()
{
var initializationTask = _initializationTask;
if (initializationTask != null)
{
return initializationTask;
}
// 此处我删减了部分线程竞争代码,因为这不是我们讨论的重点
// 此处主要目的是在该Middleware中,确保只初始化_initializationTask一次
var matcher = _matcherFactory.CreateMatcher(_endpointDataSource);
using (ExecutionContext.SuppressFlow())
{
_initializationTask = Task.FromResult(matcher);
}
}
}
上述代码的核心就是将_endpointDataSource传递给_matcherFactory,创建matcher,然后进行匹配matcher.MatchAsync(httpContext)。ASP.NET Core默认使用的 matcher 类型是DfaMatcher,DFA(Deterministic Finite Automaton)是一种被称为“确定有限状态自动机”的算法,可以从候选终结点列表中查找到匹配度最高的那个终结点。
public static class EndpointRoutingApplicationBuilderExtensions
{
public static IApplicationBuilder UseEndpoints(this IApplicationBuilder builder, Action<IEndpointRouteBuilder> configure)
{
VerifyRoutingServicesAreRegistered(builder);
VerifyEndpointRoutingMiddlewareIsRegistered(builder, out var endpointRouteBuilder);
configure(endpointRouteBuilder);
var routeOptions = builder.ApplicationServices.GetRequiredService<IOptions<RouteOptions>>();
foreach (var dataSource in endpointRouteBuilder.DataSources)
{
routeOptions.Value.EndpointDataSources.Add(dataSource);
}
return builder.UseMiddleware<EndpointMiddleware>();
}
private static void VerifyEndpointRoutingMiddlewareIsRegistered(IApplicationBuilder app, out DefaultEndpointRouteBuilder endpointRouteBuilder)
{
// 将 endpointRouteBuilder 从共享字典中取出来,如果没有,则说明之前没有调用 UseRouting
if (!app.Properties.TryGetValue(EndpointRouteBuilder, out var obj))
{
var message =
$"{nameof(EndpointRoutingMiddleware)} matches endpoints setup by {nameof(EndpointMiddleware)} and so must be added to the request " +
$"execution pipeline before {nameof(EndpointMiddleware)}. " +
$"Please add {nameof(EndpointRoutingMiddleware)} by calling '{nameof(IApplicationBuilder)}.{nameof(UseRouting)}' inside the call " +
$"to 'Configure(...)' in the application startup code.";
throw new InvalidOperationException(message);
}
endpointRouteBuilder = (DefaultEndpointRouteBuilder)obj!;
// UseRouting 和 UseEndpoints 必须添加到同一个 IApplicationBuilder 实例上
if (!object.ReferenceEquals(app, endpointRouteBuilder.ApplicationBuilder))
{
var message =
$"The {nameof(EndpointRoutingMiddleware)} and {nameof(EndpointMiddleware)} must be added to the same {nameof(IApplicationBuilder)} instance. " +
$"To use Endpoint Routing with 'Map(...)', make sure to call '{nameof(IApplicationBuilder)}.{nameof(UseRouting)}' before " +
$"'{nameof(IApplicationBuilder)}.{nameof(UseEndpoints)}' for each branch of the middleware pipeline.";
throw new InvalidOperationException(message);
}
}
}
EndpointMiddleware中间件中包含了很多异常处理和日志记录代码,为了方便查看核心逻辑,我都删除并进行了简化:
internal sealed class EndpointMiddleware
{
internal const string AuthorizationMiddlewareInvokedKey = "__AuthorizationMiddlewareWithEndpointInvoked";
internal const string CorsMiddlewareInvokedKey = "__CorsMiddlewareWithEndpointInvoked";
private readonly ILogger _logger;
private readonly RequestDelegate _next;
private readonly RouteOptions _routeOptions;
public EndpointMiddleware(
ILogger<EndpointMiddleware> logger,
RequestDelegate next,
IOptions<RouteOptions> routeOptions)
{
_logger = logger ?? throw new ArgumentNullException(nameof(logger));
_next = next ?? throw new ArgumentNullException(nameof(next));
_routeOptions = routeOptions?.Value ?? throw new ArgumentNullException(nameof(routeOptions));
}
public Task Invoke(HttpContext httpContext)
{
var endpoint = httpContext.GetEndpoint();
if (endpoint?.RequestDelegate != null)
{
// 执行该终结点的委托,并且视该中间件为终端中间件
var requestTask = endpoint.RequestDelegate(httpContext);
if (!requestTask.IsCompletedSuccessfully)
{
return requestTask;
}
return Task.CompletedTask;
}
// 若没有终结点,则继续执行下一个中间件
return _next(httpContext);
}
}
说了那么多,最后给大家总结了三张UML类图:
另外,本文仅仅提到了路由的基本使用方式和原理,如果你想要进行更加深入透彻的了解,推荐阅读蒋金楠老师的ASP.NET Core 3框架揭秘的路由部分。