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
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
namespace OcelotGateway
{
public class Program
{
public static void Main(string[] args)
{
BuildWebHost(args).Run();
}
public static IWebHost BuildWebHost(string[] args)
{
IWebHostBuilder builder = new WebHostBuilder();
//注入WebHostBuilder
return builder.ConfigureServices(service =>
{
service.AddSingleton(builder);
})
//加载configuration配置文人年
.ConfigureAppConfiguration(conbuilder =>
{
conbuilder.AddJsonFile("configuration.json");
})
.UseKestrel()
.UseUrls("http://*:5000")
.UseStartup<Startup>()
.Build();
}
}
}
同时，修改Startup.cs
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Ocelot.DependencyInjection;
using Ocelot.Middleware;
namespace OcelotGateway
{
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
public void ConfigureServices(IServiceCollection services)
{
//注入配置文件，AddOcelot要求参数是IConfigurationRoot类型，所以要作个转换
services.AddOcelot(Configuration as ConfigurationRoot);
}
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
//添加中间件
app.UseOcelot().Wait();
}
}
}
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：
[Route("demoaapi/[controller]")]
public class ValuesController : Controller
{
[HttpGet]
public IEnumerable<string> Get()
{
return new string[] { "DemoA服务", "请求" };
}
//……
}
[Route("demobapi/[controller]")]
public class ValuesController : Controller
{
[HttpGet]
public IEnumerable<string> Get()
{
return new string[] { "DemoB服务", "请求" };
}
//……
}
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 
相关文章：
-
Ocelot——初识基于.Net Core的API网关
-
Ocelot API网关的实现剖析
-
微服务网关Ocelot
-
API网关Ocelot 使用Polly 处理部分失败问题
-
谈谈微服务中的 API 网关（API Gateway）
原文：http://www.cnblogs.com/axzxs2001/p/8005041.html
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