Asp.NetCore之元件寫法

神牛003發表於2017-04-05

本章內容和大家分享的是Asp.NetCore元件寫法,在netcore中很多東西都以提供元件的方式來使用,比如MVC架構,Session,Cache,資料庫引用等; 這裡我也通過呼叫驗證碼介面來自定義個元件以此說明如何使用,以及使用時需要注意的場景;

Middleware之hello world

對於netcore來說,通常會在UseStartup<Startup>對應的Startup類中引用元件,這個Startup可以換成自己自定義的其實類,不過需要在UseStartup的時候指向她;這裡還是以Startup類為例,通過vs自動生成的檔案,在這個類中我們能看到Configure方法體裡面包含了:app.UseMvc(),app.UseStaticFiles(),app.xxx()等一些列自帶的元件,下面來看下自定義個hello world中元件例項,首先使用靜態擴充套件方法擴充套件IApplicationBuilder

 1  public static class MiddlewareExtends
 2     {
 3         /// <summary>
 4         /// 測試用例中介軟體
 5         /// </summary>
 6         /// <param name="builder"></param>
 7         /// <returns></returns>
 8         public static IApplicationBuilder UseTest(this IApplicationBuilder builder)
 9         {
10             return builder.UseMiddleware<TestMiddleware>();
11         }
12 
13     }

使用 builder.UseMiddleware<TestMiddleware>() 來新增自定義元件,元件實現程式碼如下:

 1     public class TestMiddleware
 2     {
 3         private RequestDelegate _requestDelegate;
 4         public TestMiddleware(RequestDelegate requestDelegate)
 5         {
 6             _requestDelegate = requestDelegate;
 7         }
 8 
 9         public Task Invoke(HttpContext context)
10         {
11 
12             context.Items["TestMiddleware"] = "hello world,我是TestMiddleware。";
13 
14             return _requestDelegate(context);
15         }
16     }

以上是最基礎的元件格式;注:

1. 元件必須要有 public Task Invoke(HttpContext context) ,HttpContext是咋們http上下文,Invoke()委託方法,每次程式被訪問時就會進入Invoke;

2. 要有 public delegate Task RequestDelegate(HttpContext context); 委託方法,來響應http請求;

到這裡咋們hello world就完成了,為了測試方法,我們直接在action中寫入如下程式碼:

1  public IActionResult About()
2         {
3 
4             ViewData["Message"] = HttpContext.Items["TestMiddleware"];
5             return View();
6         }

執行結果:

 

元件非同步寫法

 1  public class TestMiddleware
 2     {
 3         private RequestDelegate _requestDelegate;
 4         public TestMiddleware(RequestDelegate requestDelegate)
 5         {
 6             _requestDelegate = requestDelegate;
 7         }
 8 
 9         public async Task Invoke(HttpContext context)
10         {
11 
12             context.Items["TestMiddleware"] = "hello world,我是asyncTestMiddleware。";
13 
14             await _requestDelegate(context);
15         }
16     }

僅僅需要async 和 await 組合修飾就行了;

 

.netcore自定義驗證碼元件

 1  /// <summary>
 2     /// 文字驗證碼
 3     /// </summary>
 4     public class WenZiCodeMiddleware
 5     {
 6         private RequestDelegate _requestDelegate;
 7         public WenZiCodeMiddleware(RequestDelegate requestDelegate)
 8         {
 9             _requestDelegate = requestDelegate;
10         }
11 
12         public async Task Invoke(HttpContext context)
13         {
14 
15             var url = "http://localhost:1001/shenniuapi/WenZiValidateCode";
16             using (HttpClient client = new HttpClient())
17             {
18                 client.Timeout = TimeSpan.FromSeconds(60);
19 
20                 var str = "{\"UserName\": \"神牛步行3\",\"UserPwd\": \"4297f44b13955235245b2497399d7a93\",\"Token\": \"008我是測試\"}";
21                 var content = new StringContent(str, Encoding.UTF8, "application/x-www-form-urlencoded");
22                 content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
23                 var result01 = client.PostAsync(url, content).Result;
24                 var stream = await result01.Content.ReadAsStreamAsync();
25                 using (var reader = new StreamReader(stream))
26                 {
27                     var result02 = await reader.ReadToEndAsync();
28                     context.Items["codedata"] = result02;
29                 }
30             }
31 
32             await _requestDelegate(context);
33         }
34     }

我們同樣需要再靜態擴充套件方法裡面新增如下程式碼,來加入元件:

1 /// <summary>
2         /// 文字驗證碼中介軟體
3         /// </summary>
4         /// <param name="builder"></param>
5         /// <returns></returns>
6         public static IApplicationBuilder UseWenZiValidateCode(this IApplicationBuilder builder)
7         {
8             return builder.UseMiddleware<WenZiCodeMiddleware>();
9         }

在Configure方法中,引用元件: app.UseWenZiValidateCode(); ;Action中,使用元件:

1  public FileResult GetCode()
2         {
3             var data = HttpContext.Items["codedata"].ToString();
4             var code = JsonConvert.DeserializeObject<MoValidateCodeResponse>(data);
5             return File(code.CodeStream, "image/jpeg");
6         }

View試圖中程式碼:

1 GetCode:<img src="/home/GetCode" data-src="/home/GetCode" />

效果展示:

這裡需要考慮場景是,我們上面提及到的Invoke方法是任意請求都會進入,那驗證碼這種功能做成元件是否不是很合理,因為驗證碼也只有在登陸介面或驗證的介面需要用到而已,如我們上面寫的驗證碼元件,每次都會被程式執行這顯然不合理,因此個人認為如果你需要自定義元件,那麼需要考量:是否每次請求都需要進入您的元件服務,如果不需要的話,那其實沒必要弄一個元件,當然感覺很高大上;因此這裡我不得不使用靜態擴充套件方法(當然還有其他方式)來重寫獲取驗證碼的方法;

 

靜態擴充套件方法重寫驗證碼元件

由於上面我們在新增元件時有一個靜態類了,那麼我們直接在上面補充擴充套件方法:

 1 /// <summary>
 2         /// 文字驗證碼
 3         /// </summary>
 4         /// <param name="context"></param>
 5         /// <returns></returns>
 6         public static async Task<MoValidateCodeResponse> WenZiCode(this HttpContext context)
 7         {
 8             var code = default(MoValidateCodeResponse);
 9             try
10             {
11                 var url = "http://localhost:1001/shenniuapi/WenZiValidateCode";
12                 using (HttpClient client = new HttpClient())
13                 {
14                     client.Timeout = TimeSpan.FromSeconds(60);
15 
16                     var str = "{\"UserName\": \"神牛步行3\",\"UserPwd\": \"4297f44b13955235245b2497399d7a93\",\"Token\": \"008我是測試\"}";
17                     var content = new StringContent(str, Encoding.UTF8, "application/x-www-form-urlencoded");
18                     content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
19                     var result01 = client.PostAsync(url, content).Result;
20                     var stream = await result01.Content.ReadAsStreamAsync();
21                     using (var reader = new StreamReader(stream))
22                     {
23                         var result02 = await reader.ReadToEndAsync();
24                         code = await JsonConvert.DeserializeObjectAsync<MoValidateCodeResponse>(result02);
25                     }
26                 }
27             }
28             catch (Exception ex)
29             {
30             }
31             return code;
32         }

對應的驗證碼實體類:

 1  /// <summary>
 2     /// 神牛介面返回基類
 3     /// </summary>
 4     public class MoShenNiuBaseResponse
 5     {
 6         /// <summary>
 7         /// 返回狀態: 0:失敗 1:成功
 8         /// </summary>
 9         public int Status { get; set; }
10 
11         /// <summary>
12         /// 錯誤資訊
13         /// </summary>
14         public string Msg { get; set; }
15     }
16 
17     /// <summary>
18     /// 驗證碼返回類
19     /// </summary>
20     public class MoValidateCodeResponse : MoShenNiuBaseResponse
21     {
22 
23         public MoValidateCodeResponse()
24         {
25             this.ImgCode = new List<MoImgCode>();
26         }
27 
28         /// <summary>
29         /// 驗證碼型別
30         /// </summary>
31         public string Code { get; set; }
32 
33         /// <summary>
34         /// 驗證碼圖片流
35         /// </summary>
36         public byte[] CodeStream { get; set; }
37 
38         /// <summary>
39         /// 圖片驗證座標
40         /// </summary>
41         public List<MoImgCode> ImgCode;
42     }
43 
44     /// <summary>
45     /// 圖片驗證碼座標
46     /// </summary>
47     public class MoImgCode
48     {
49         public string Index { get; set; }
50 
51         public string IndexType { get; set; }
52 
53         public string ImgUrl { get; set; }
54 
55         public Point Point_A { get; set; }
56 
57         public Point Point_B { get; set; }
58 
59         public bool IsChoice { get; set; }
60     }
61 
62     public class Point
63     {
64         public int X { get; set; }
65         public int Y { get; set; }
66     }
View Code

這個時候同樣來到Action中:

1  public async Task<FileResult> GetCodeAsync()
2         {
3             var code = await HttpContext.WenZiCode();
4 
5             return File(code.CodeStream, "image/jpeg");
6         }

修改view試圖程式碼,增加點選驗證碼圖片重新獲取新的驗證碼:

 1 <style type="text/css">
 2     img{cursor:pointer}
 3 </style>
 4 <h3>@ViewData["Message"]</h3>
 5 <h3>@ViewData["codedata"]</h3>
 6 GetCode:<img src="/home/GetCode" data-src="/home/GetCode" />
 7 GetCodeAsync:<img src="/home/GetCodeAsync" data-src="/home/GetCodeAsync" />
 8 
 9 <script src="~/lib/jquery/dist/jquery.js"></script>
10 <script>
11     $(function () {
12         $("img").on("click", function () {
13             var img = this;
14             var nowTime = new Date().getTime();
15             var src = $(img).attr("data-src") + "?t=" + nowTime;
16             $(img).attr("src", src);
17         });
18     })
19 </script>

效果圖:

以上就是本篇的所有內容,旨在分享怎麼寫一個元件和什麼時候用元件合適,謝謝大家支援和點贊。

 

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