asp.net MVC设计模式中使用iTextSharp实现html字…

2018-07-24 08:08:26来源：博客园阅读 ()

　　因个人需求，需要将html格式转换成PDF并加上水印图片。于是乎第一次接触这种需求的小菜鸟博主我，在某度搜索引擎上不断的查阅关键字资料、踩坑，终于有了一个相应的解决方案。以下是解决步骤，记录下来方便以后的回顾，以及各位大神们的品鉴。

　　1、在 NuGet 搜索 itextsharp 关键字下载以下截图圈中的两个包，一般下载完后项目会自引用。

　　2、在项目文件中引入以下命名空间（建议下面提及的代码封装成类库，方便项目间调用，个人取舍）

　　3、Html字符串转pdf文件流，加水印图片以及未加水印重载精简帮助类（由博主踩坑整理，仅完成个人业务需求）

 1     /// <summary>
 2     /// Html字符串转PDF输出帮助类
 3     /// </summary>
 4     public class HtmlToPdfHelper
 5     {
 6         #region HtmlToPDF
 7 
 8         /// <summary>
 9         /// 判断是否有乱码
10         /// </summary>
11         /// <param name="txt"></param>
12         /// <returns></returns>
13         private static bool IsMessyCode(string txt)
14         {
15             var bytes = Encoding.UTF8.GetBytes(txt);
16             for (var i = 0; i < bytes.Length; i++)
17             {
18                 if (i < bytes.Length - 3)
19                     if (bytes[i] == 239 && bytes[i + 1] == 191 && bytes[i + 2] == 189)
20                     {
21                         return true;
22                     }
23             }
24             return false;
25         }
26 
27         /// <summary>
28         /// 将Html字符串 输出到PDF档里
29         /// </summary>
30         /// <param name="htmlText"></param>
31         /// <returns></returns>
32         public static byte[] ConvertHtmlTextToPdf(string htmlText)
33         {
34             return ConvertHtmlTextToPdf(htmlText, "", 0, 0, 0, 0);
35         }
36 
37         /// <summary>
38         /// 将Html字符串 输出到PDF档里,并添加水印
39         /// </summary>
40         /// <param name="htmlText">网页代码</param>
41         /// <param name="picPath">水印路径</param>
42         /// <param name="left">距离左边距离</param>
43         /// <param name="top">距顶部距离</param>
44         /// <param name="width">水印宽度</param>
45         /// <param name="height">水印高度</param>
46         /// <returns></returns>
47         public static byte[] ConvertHtmlTextToPdf(string htmlText, string picPath, int left, int top, int width, int height)
48         {
49             if (string.IsNullOrEmpty(htmlText))
50             {
51                 return null;
52             }
53             //避免当htmlText无任何html tag标签的纯文字时，转PDF时会挂掉，所以一律加上<p>标签
54             htmlText = "<p>" + htmlText + "</p>";
55             MemoryStream outputStream = new MemoryStream();//要把PDF写到哪个串流
56             byte[] data = Encoding.UTF8.GetBytes(htmlText);//字串转成byte[]
57             MemoryStream msInput = new MemoryStream(data);
58             Document doc = new Document();//要写PDF的文件，建构子没填的话预设直式A4
59             PdfWriter writer = PdfWriter.GetInstance(doc, outputStream);
60             //指定文件预设开档时的缩放为100%
61             PdfDestination pdfDest = new PdfDestination(PdfDestination.XYZ, 0, doc.PageSize.Height, 1f);
62             //开启Document文件 
63             doc.Open();
64 
65             //写入水印图片
66             if (!string.IsNullOrEmpty(picPath))
67             {
68                 Image img = Image.GetInstance(picPath);
69                 //设置图片的位置
70                 img.SetAbsolutePosition(width + left, (doc.PageSize.Height - height) - top);
71                 //设置图片的大小
72                 img.ScaleAbsolute(width, height);
73                 doc.Add(img);
74             }
75             try
76             {
77                 //使用XMLWorkerHelper把Html parse到PDF档里
79                 XMLWorkerHelper.GetInstance().ParseXHtml(writer, doc, msInput, null, Encoding.UTF8);
80                 //将pdfDest设定的资料写到PDF档
81                 PdfAction action = PdfAction.GotoLocalPage(1, pdfDest, writer);
82                 writer.SetOpenAction(action);
83             }
84             catch (Exception)
85             {
86                 return null;
87             }
88             doc.Close();
89             msInput.Close();
90             outputStream.Close();
91             //回传PDF档案 
92             return outputStream.ToArray();
94         }
95 
96         #endregion
97 
98     }

　　4、获取网页字符串方法

 1         /// <summary>
 2         /// 获取网站内容，包含了 HTML+CSS+JS
 3         /// </summary>
 4         /// <returns>String返回网页信息</returns>
 5         public static string GetWebContent(string inpath)
 6         {
 7             try
 8             {
 9                 WebClient myWebClient = new WebClient();
10                 //获取或设置用于向Internet资源的请求进行身份验证的网络凭据
11                 myWebClient.Credentials = CredentialCache.DefaultCredentials;
12                 //从指定网站下载数据
13                 Byte[] pageData = myWebClient.DownloadData(inpath);
14                 //如果获取网站页面采用的是GB2312，则使用这句
15                 string pageHtml = Encoding.UTF8.GetString(pageData);
16                 bool isBool = IsMessyCode(pageHtml);//判断使用哪种编码 读取网页信息
17                 if (!isBool)
18                 {
19                     string pageHtml1 = Encoding.UTF8.GetString(pageData);
20                     pageHtml = pageHtml1;
21                 }
22                 else
23                 {
24                     string pageHtml2 = Encoding.Default.GetString(pageData);
25                     pageHtml = pageHtml2;
26                 }
27                 return pageHtml;
28             }
29             catch (WebException webEx)
30             {
31                 return webEx.Message;
32             }
33         }

　　5、MVC设计模式下获取控制器视图Html方法，很XX的一个问题就是只能获取调用此方法的控制器下所有视图，不能跨控制器获取视图，有待优化

 1         /// <summary>
 2         /// 获取MVC视图Html
 3         /// </summary>
 4         /// <param name="context">控制器上下文</param>
 5         /// <param name="viewName">视图名称</param>
 6         /// <param name="param"></param>
 7         /// <returns></returns>
 8         public static string GetViewHtml(ControllerContext context, string viewName)
 9         {
10             if (string.IsNullOrEmpty(viewName))
11                 viewName = context.RouteData.GetRequiredString("action");
12             using (var sw = new StringWriter())
13             {
14                 ViewEngineResult viewResult = ViewEngines.Engines.FindPartialView(context, viewName);
15                 var viewContext = new ViewContext(context, viewResult.View, context.Controller.ViewData, context.Controller.TempData, sw);
16                 try
17                 {
18                     viewResult.View.Render(viewContext, sw);
19                 }
20                 catch (Exception ex)
21                 {
22                     throw;
23                 }
24 
25                 return sw.GetStringBuilder().ToString();
26             }
27         }

　　6、将pdf流输出至客户浏览器下载方法

 1         /// <summary>
 2         /// 将pdf文件流输出至浏览器下载
 3         /// </summary>
 4         /// <param name="pdfFile">PDF文件流</param>
 5         public static void PdfDownload(byte[] pdfFile)
 6         {
 7             byte[] buffer = pdfFile;
 8             Stream iStream = new MemoryStream(buffer);
 9             try
10             {
11                 int length;
12                 long dataToRead;
13                 string filename = DateTime.Now.ToString("yyyyMMddHHmmss") + ".pdf";//保存的文件名称
14                 dataToRead = iStream.Length;
15                 HttpContext.Current.Response.Clear();
16                 HttpContext.Current.Response.ClearHeaders();
17                 HttpContext.Current.Response.ClearContent();
18                 HttpContext.Current.Response.ContentType = "application/pdf"; //文件类型 
19                 HttpContext.Current.Response.AddHeader("Content-Length", dataToRead.ToString());//添加文件长度，进而显示进度 
20                 HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(filename, Encoding.UTF8));
21                 while (dataToRead > 0)
22                 {
23                     if (HttpContext.Current.Response.IsClientConnected)
24                     {
25                         length = buffer.Length;
26                         HttpContext.Current.Response.OutputStream.Write(buffer, 0, length);
27                         HttpContext.Current.Response.Flush();
28                         buffer = new Byte[length];
29                         dataToRead = dataToRead - length;
30                     }
31                     else
32                     {
33                         dataToRead = -1;
34                     }
35                 }
36             }
37             catch (Exception ex)
38             {
39                 HttpContext.Current.Response.Write("文件下载时出现错误!");
40             }
41             finally
42             {
43                 if (iStream != null)
44                 {
45                     iStream.Close();
46                 }
47                 //结束响应，否则将导致网页内容被输出到文件，进而文件无法打开  
48                 HttpContext.Current.Response.Flush();
49                 HttpContext.Current.Response.End();
50 
51             }
52         }

　　7、MVC控制器下调用Demo（步骤4、6 方法封装至帮助类）

 1     public class HomeController : Controller
 2     {
 3         //
 4         // GET: /Home/
 5 
 6         public ActionResult Index()
 7         {
 8             //从网址下载Html字符串(方法一)
 9             string inpath = System.Web.HttpContext.Current.Server.MapPath("~/PDFTemplate/test.html");
10             string htmlText = HtmlToPdfHelper.GetWebContent(inpath);//此处调用步骤4方法
11 
12             //获取MVC视图Html字符串(方法二)
13             //string htmlText = GetViewHtml(ControllerContext, "Test");//此处调用步骤5方法
14 
15             //水印图片路径
16             string picPath = Server.MapPath("~/PDFTemplate/TemplateImg/authentication-iocn.png");
17             //html转pdf并加上水印
18             byte[] pdfFile = HtmlToPdfHelper.ConvertHtmlTextToPdf(htmlText, picPath, 100, 200, 100, 100);
19             //输出至客户端
20             HtmlToPdfHelper.PdfDownload(pdfFile);//此处调用步骤6方法
21 
22             return View();
23         }
24 
25         public ActionResult Test()
26         {
27             return View();
28         }
29 
30         /// <summary>
31         /// 获取MVC视图Html
32         /// </summary>
33         /// <param name="context"></param>
34         /// <param name="viewName">视图名称</param>
35         /// <returns></returns>
36         public static string GetViewHtml(ControllerContext context, string viewName)
37         {
38             if (string.IsNullOrEmpty(viewName))
39                 viewName = context.RouteData.GetRequiredString("action");
40             using (var sw = new StringWriter())
41             {
42                 ViewEngineResult viewResult = ViewEngines.Engines.FindPartialView(context, viewName);
43                 var viewContext = new ViewContext(context, viewResult.View, context.Controller.ViewData,
44                     context.Controller.TempData, sw);
45                 try
46                 {
47                     viewResult.View.Render(viewContext, sw);
48                 }
49                 catch (Exception ex)
50                 {
51                     throw;
52                 }
53 
54                 return sw.GetStringBuilder().ToString();
55             }
56         }
57     }