.NET Core 实例接口代理转发
先講講本文的開發(fā)背景吧..
在如今前后端分離的大背景下,咱的客戶又有要求啦~
要前后端分離~ 然因?yàn)榉N種原因..沒辦法用用純前端的框架(其實(shí)是學(xué)習(xí)成本高,又沒錢請(qǐng)前端開發(fā)人員)...
所以最終決定了一種方案..
那就是采用MVC(只處理前端視圖層,單純是為了托管在.net core上)+Webapi的方式來實(shí)現(xiàn)前后端分離(講真,很奇葩)..
那么問題就隨之而來了.
現(xiàn)在主流的前端框架都是托管在nodejs上,是通過axios來訪問后端API,可以通過配置axios的代理配置(proxyTable)來實(shí)現(xiàn)跨域訪問.
那么我們的JS運(yùn)行在MVC上,托管在.net core上..那咋辦呢?..沒有現(xiàn)成的轉(zhuǎn)發(fā)輪子..我們只有自己造了..
所以這就是本篇的背景 - -.~
正文
幸運(yùn)的是ASP.NET Core 給我們提供了強(qiáng)大的中間件模式.
我們完全可以通過定義一個(gè)轉(zhuǎn)發(fā)中間件的形式來實(shí)現(xiàn)代理接口轉(zhuǎn)發(fā),流程如圖:
廢話不多說,我們來創(chuàng)建我們的中間件:
一.創(chuàng)建檢測(cè)約定URL的接口與實(shí)現(xiàn)
首先定義一個(gè)接口IUrlRewriter 用來檢測(cè)我們的URL是否有對(duì)應(yīng)前綴,如果有,則產(chǎn)生新的URL地址:
這里我們定義接口是為了方便以后更好的更換注入類來實(shí)現(xiàn)快速更換檢測(cè)前綴的規(guī)則.
public interface IUrlRewriter
{
Task?RewriteUri(HttpContext context);
}
實(shí)現(xiàn)這個(gè)接口,如下(解釋都在注釋里了):
public class PrefixRewriter : IUrlRewriter
{
private readonly PathString _prefix; //前綴值
private readonly string _newHost; //轉(zhuǎn)發(fā)的地址
public PrefixRewriter(PathString prefix, string newHost)
{
_prefix=prefix;
_newHost=newHost;
}
public Task?RewriteUri(HttpContext context)
{
if (context.Request.Path.StartsWithSegments(_prefix))//判斷訪問是否含有前綴
{
var newUri=context.Request.Path.Value.Remove(0, _prefix.Value.Length) + context.Request.QueryString;
var targetUri=new Uri(_newHost + newUri);
return Task.FromResult(targetUri);
}
return Task.FromResult((Uri)null);
}
}二.創(chuàng)建代理轉(zhuǎn)發(fā)需要的ProxyHttpClient
創(chuàng)建獨(dú)立的ProxyHttpClient,主要是為了區(qū)分代理轉(zhuǎn)發(fā)的httpClient,方便后期添加日志或做別的處理.代碼如下:
public class ProxyHttpClient
{
public HttpClient Client { get; private set; }
public ProxyHttpClient(HttpClient httpClient)
{
Client=httpClient;
}
}三.創(chuàng)建代理轉(zhuǎn)發(fā)的中間件
代碼如下,中間件嘛,主要就是Invoke方法了,說明可以看注釋.
public class ProxyMiddleware
{
private ProxyHttpClient _proxyHttpClient;
private const string CDN_HEADER_NAME="Cache-Control";
private static readonly string[] NotForwardedHttpHeaders=new[] { "Connection", "Host" };
private readonly RequestDelegate _next;
private readonly ILogger?_logger;
public ProxyMiddleware(
RequestDelegate next,
ILogger?logger,
ProxyHttpClient proxyHttpClient
)
{
_next=next;
_logger=logger;
_proxyHttpClient=proxyHttpClient;
}
///
/// 通過中間件,攔截訪問,檢測(cè)前綴,并轉(zhuǎn)發(fā)
///
///
///
///
public async Task Invoke(HttpContext context, IUrlRewriter urlRewriter)
{
var targetUri=await urlRewriter.RewriteUri(context);
if (targetUri !=null)
{
var requestMessage=GenerateProxifiedRequest(context, targetUri);
await SendAsync(context, requestMessage);
return;
}
await _next(context);
}
private async Task SendAsync(HttpContext context, HttpRequestMessage requestMessage)
{
using (var responseMessage=await _proxyHttpClient.Client.SendAsync(requestMessage, HttpCompletionOption.ResponseHeadersRead, context.RequestAborted))
{
context.Response.StatusCode=(int)responseMessage.StatusCode;
foreach (var header in responseMessage.Headers)
{
context.Response.Headers[header.Key]=header.Value.ToArray();
}
foreach (var header in responseMessage.Content.Headers)
{
context.Response.Headers[header.Key]=header.Value.ToArray();
}
context.Response.Headers.Remove("transfer-encoding");
if (!context.Response.Headers.ContainsKey(CDN_HEADER_NAME))
{
context.Response.Headers.Add(CDN_HEADER_NAME, "no-cache, no-store");
}
await responseMessage.Content.CopyToAsync(context.Response.Body);
}
}
private static HttpRequestMessage GenerateProxifiedRequest(HttpContext context, Uri targetUri)
{
var requestMessage=new HttpRequestMessage();
CopyRequestContentAndHeaders(context, requestMessage);
requestMessage.RequestUri=targetUri;
requestMessage.Headers=targetUri;
requestMessage.Method=GetMethod(context.Request.Method);
return requestMessage;
}
private static void CopyRequestContentAndHeaders(HttpContext context, HttpRequestMessage requestMessage)
{
var requestMethod=context.Request.Method;
if (!HttpMethods.IsGet(requestMethod) &&
!HttpMethods.IsHead(requestMethod) &&
!HttpMethods.IsDelete(requestMethod) &&
!HttpMethods.IsTrace(requestMethod))
{
var streamContent=new StreamContent(context.Request.Body);
requestMessage.Content=streamContent;
}
foreach (var header in context.Request.Headers)
{
if (!NotForwardedHttpHeaders.Contains(header.Key))
{
if (header.Key !="User-Agent")
{
if (!requestMessage.Headers.TryAddWithoutValidation(header.Key, header.Value.ToArray()) && requestMessage.Content !=null)
{
requestMessage.Content?.Headers.TryAddWithoutValidation(header.Key, header.Value.ToArray());
}
}
else
{
string userAgent=header.Value.Count > 0 ? (header.Value[0] + " " + context.TraceIdentifier) : string.Empty;
if (!requestMessage.Headers.TryAddWithoutValidation(header.Key, userAgent) && requestMessage.Content !=null)
{
requestMessage.Content?.Headers.TryAddWithoutValidation(header.Key, userAgent);
}
}
}
}
}
private static HttpMethod GetMethod(string method)
{
if (HttpMethods.IsDelete(method)) return HttpMethod.Delete;
if (HttpMethods.IsGet(method)) return HttpMethod.Get;
if (HttpMethods.IsHead(method)) return HttpMethod.Head;
if (HttpMethods.IsOptions(method)) return HttpMethod.Options;
if (HttpMethods.IsPost(method)) return HttpMethod.Post;
if (HttpMethods.IsPut(method)) return HttpMethod.Put;
if (HttpMethods.IsTrace(method)) return HttpMethod.Trace;
return new HttpMethod(method);
}
}四.注入和啟用我們的中間件和ProxyHttpClient
我們?cè)赟tartup的ConfigureServices中添加如下代碼,注入我們的HttpClient與IUrlRewriter,如下:
services.AddHttpClient()
.ConfigurePrimaryHttpMessageHandler(x=> new HttpClientHandler()
{
AllowAutoRedirect=false,
MaxConnectionsPerServer=int.MaxValue,
UseCookies=false,
}); //注入我們定義的HttpClient
services.AddSingleton(new PrefixRewriter("/webapp", "localhost:63445"));//這里填寫前綴與需要轉(zhuǎn)發(fā)的地址
然后在Startup的Configure中,啟動(dòng)我們的中間件,如下:
app.UseMiddleware();
五.測(cè)試中間件效果
我們編寫前端代碼如下:
created: function () {
this.mockTableData1();
axios.get("/webapp/api/values/get", "123").then(res=> { alert(res.data[0]) });
axios.post("/webapp/api/values/post",{value: 'david'}).then(res=> { alert(res.data.message) });
}
在另外的WebApi項(xiàng)目,編寫接口如下:
[HttpGet]
public ActionResult> Get()
{
return new string[] { "value1", accstring.ToString() };
}
[HttpPost]
public AjaxResult Post(dynamic value)
{
string aaa=JsonConvert.SerializeObject(value);
return Success("OK");
}
效果如下,可以看到我們的視圖正確的獲取到了返回值:
寫在最后
這里我們通過中間件的形式實(shí)現(xiàn)了接口的代理轉(zhuǎn)發(fā),在具體的使用過程中肯定還會(huì)有一些小問題,而且這里我們只實(shí)現(xiàn)了Http的轉(zhuǎn)發(fā).ws的則沒有.
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