Ocelot是一个.net core框架下的网关的开源项目，下图是官方给出的基础实现图，即把后台的多个服务统一到网关处，前端应用：桌面端，web端，app端都只用访问网关即可。
Ocelot的实现原理就是把客户端对网关的请求(Request)，按照configuration.json的映射配置，转发给对应的后端http service，然后从后端http service获取响应(Response)后，再返回给客户端。当然有了网关后，我们可以在网关这层去做统一验证，也可以在网关处统一作监控。
接下来做个Demo
新建三个asp.net core web aip项目：
OcelotGateway网关项目，端口是5000
DemoAAPI项目A，端口是5001
DemoBAPI项目B，端口是5002
(注：端口可以在每个项目的Properties下的launchSettings.json中修改，发布后的端口可以在Program.cs中用UseUrls(“http://*:5000”)来修改)
对于OcelotGateway：
引用Ocelot的Nuget包：
视图->其他窗口->程序包管理控制台：Install-Package Ocelot
或项目右键“管理Nuget程序包”，在浏览里查找Ocelot进行安装
在OcelotGateway项目中添加一个configuration.json文件，关把它的属性“复制到输出目录”，设成“始终复制”，内容如下：
{
"ReRoutes": [
{
"DownstreamPathTemplate": "/demoaapi/values",
"DownstreamScheme": "http",
"DownstreamPort": 5001,
"DownstreamHost": "localhost",
"UpstreamPathTemplate": "/demoaapi/values",
"UpstreamHttpMethod": [ "Get" ],
"QoSOptions": {
"ExceptionsAllowedBeforeBreaking": 3,
"DurationOfBreak": 10,
"TimeoutValue": 5000
},
"HttpHandlerOptions": {
"AllowAutoRedirect": false,
"UseCookieContainer": false
},
"AuthenticationOptions": {
"AuthenticationProviderKey": "",
"AllowedScopes": []
}
},
{
"DownstreamPathTemplate": "/demobapi/values",
"DownstreamScheme": "http",
"DownstreamPort": 5002,
"DownstreamHost": "localhost",
"UpstreamPathTemplate": "/demobapi/values",
"UpstreamHttpMethod": [ "Get" ],
"QoSOptions": {
"ExceptionsAllowedBeforeBreaking": 3,
"DurationOfBreak": 10,
"TimeoutValue": 5000
},
"HttpHandlerOptions": {
"AllowAutoRedirect": false,
"UseCookieContainer": false
},
"AuthenticationOptions": {
"AuthenticationProviderKey": "",
"AllowedScopes": []
}
}
]
}
接下来对OcelotGateway的Program.cs进行改造
1 using Microsoft.AspNetCore.Hosting; 2 3 using Microsoft.Extensions.Configuration; 4 5 using Microsoft.Extensions.DependencyInjection; 6 7 8 9 namespace OcelotGateway 10 11 { 12 13 public class Program 14 15 { 16 17 public static void Main(string[] args) 18 19 { 20 21 BuildWebHost(args).Run(); 22 23 } 24 25 public static IWebHost BuildWebHost(string[] args) 26 27 { 28 29 IWebHostBuilder builder = new WebHostBuilder(); 30 31 //注入WebHostBuilder 32 33 return builder.ConfigureServices(service => 34 35 { 36 37 service.AddSingleton(builder); 38 39 }) 40 41 //加载configuration配置文人年 42 43 .ConfigureAppConfiguration(conbuilder => 44 45 { 46 47 conbuilder.AddJsonFile("configuration.json"); 48 49 }) 50 51 .UseKestrel() 52 53 .UseUrls("http://*:5000") 54 55 .UseStartup<Startup>() 56 57 .Build(); 58 59 } 60 61 } 62 63 }
同时，修改Startup.cs
1 using Microsoft.AspNetCore.Builder; 2 3 using Microsoft.AspNetCore.Hosting; 4 5 using Microsoft.Extensions.Configuration; 6 7 using Microsoft.Extensions.DependencyInjection; 8 9 using Ocelot.DependencyInjection; 10 11 using Ocelot.Middleware; 12 13 14 15 namespace OcelotGateway 16 17 { 18 19 public class Startup 20 21 { 22 23 public Startup(IConfiguration configuration) 24 25 { 26 27 Configuration = configuration; 28 29 } 30 31 public IConfiguration Configuration { get; } 32 33 public void ConfigureServices(IServiceCollection services) 34 35 { 36 37 //注入配置文件，AddOcelot要求参数是IConfigurationRoot类型，所以要作个转换 38 39 services.AddOcelot(Configuration as ConfigurationRoot); 40 41 } 42 43 public void Configure(IApplicationBuilder app, IHostingEnvironment env) 44 45 { 46 47 //添加中间件 48 49 app.UseOcelot().Wait(); 50 51 } 52 53 } 54 55 }
为了测试数据好看，我们把DemoAAPI项目和DemoBAPI项目的ValuesController作一下修改：
1 [Route("demoaapi/[controller]")] 2 3 public class ValuesController : Controller 4 5 { 6 7 [HttpGet] 8 9 public IEnumerable<string> Get() 10 11 { 12 13 return new string[] { "DemoA服务", "请求" }; 14 15 } 16 17 //…… 18 19 } 20 21 22 23 [Route("demobapi/[controller]")] 24 25 public class ValuesController : Controller 26 27 { 28 29 [HttpGet] 30 31 public IEnumerable<string> Get() 32 33 { 34 35 return new string[] { "DemoB服务", "请求" }; 36 37 } 38 39 //…… 40 41 }
最后在解决方案属性->多个启动项目中，把DemoAAPI，DemoBAPI，OcelotGateway都设成启动，开始启动解决方案，效果如下图 
《基于.net core微服务架构视频》
http://edu.51cto.com/course/13342.html