HttpWebRequest类

HttpWebRequest类与HttpRequest类的区别。

HttpRequest类的对象用于服务器端，获取客户端传来的请求的信息，包括HTTP报文传送过来的所有信息。而HttpWebRequest用于客户端，拼接请求的HTTP报文并发送等。

HttpWebRequest这个类非常强大，强大的地方在于它封装了几乎HTTP请求报文里需要用到的东西，以致于能够能够发送任意的HTTP请求并获得服务器响应(Response)信息。采集信息常用到这个类。在学习这个类之前，首先有必要了解下HTTP方面的知识。

一、简单示例
　　我们先来一个最简单的，就是紧紧输入一个网址就获取响应。代码如下：

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class Program
{
static void Main(string[] args)
{
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(“http://www.baidu.com”); //创建一个请求示例
HttpWebResponse response = (HttpWebResponse)request.GetResponse();　　//获取响应，即发送请求
Stream responseStream = response.GetResponseStream();
StreamReader streamReader = new StreamReader(responseStream, Encoding.UTF8);
string html = streamReader.ReadToEnd();
Console.WriteLine(html);

        Console.ReadKey();}
}

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　　OK，就是这么简单了，真的这么简单吗？发送一个HTTP请求真的这么简单。但是要做出很多功能就不简单了。你需要详细了解下HTTP方面的知识，比如HTTP请求报文之类的。

二、模拟登录
　　下面来个复杂点的，这次是获取登录之后的页面。登录之后的请求用什么实现呢？呵呵，用到是cookie。在拼接HTTP请求的时候，连着cookie也发送过去。

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namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
HttpHeader header = new HttpHeader();
header.accept = “image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/x-silverlight, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-ms-application, application/x-ms-xbap, application/vnd.ms-xpsdocument, application/xaml+xml, application/x-silverlight-2-b1, /”;
header.contentType = “application/x-www-form-urlencoded”;
header.method = “POST”;
header.userAgent = “Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022)”;
header.maxTry = 300;

        //在这里自己拼接一下Cookie，不用复制过来的那个GetCookie方法了，原来的那个写法还是比较严谨的CookieContainer cc = new CookieContainer();Cookie cUserName = new Cookie("cSpaceUserEmail", "742783833%40qq.com");cUserName.Domain = ".7soyo.com";Cookie cUserPassword = new Cookie("cSpaceUserPassWord", "4f270b36a4d3e5ee70b65b1778e8f793");cUserPassword.Domain = ".7soyo.com";cc.Add(cUserName);cc.Add(cUserPassword);string html = HTMLHelper.GetHtml("http://user.7soyo.com/CollectUser/List", cc, header);FileStream fs = new FileStream(@"D:\\123.txt",FileMode.CreateNew,FileAccess.ReadWrite);fs.Write(Encoding.UTF8.GetBytes(html),0,html.Length);fs.Flush();fs.Dispose();Console.WriteLine(html);Console.ReadKey();}
}public class HTMLHelper
{/// <summary>/// 获取CooKie/// </summary>/// <param name="loginUrl"></param>/// <param name="postdata"></param>/// <param name="header"></param>/// <returns></returns>public static CookieContainer GetCooKie(string loginUrl, string postdata, HttpHeader header){HttpWebRequest request = null;HttpWebResponse response = null;try{CookieContainer cc = new CookieContainer();request = (HttpWebRequest)WebRequest.Create(loginUrl);request.Method = header.method;request.ContentType = header.contentType;byte[] postdatabyte = Encoding.UTF8.GetBytes(postdata);     //提交的请求主体的内容request.ContentLength = postdatabyte.Length;    //提交的请求主体的长度request.AllowAutoRedirect = false;request.CookieContainer = cc;request.KeepAlive = true;//提交请求Stream stream;stream = request.GetRequestStream();stream.Write(postdatabyte, 0, postdatabyte.Length);     //带上请求主体stream.Close();//接收响应response = (HttpWebResponse)request.GetResponse();      //正式发起请求response.Cookies = request.CookieContainer.GetCookies(request.RequestUri);CookieCollection cook = response.Cookies;//Cookie字符串格式string strcrook = request.CookieContainer.GetCookieHeader(request.RequestUri);return cc;}catch (Exception ex){throw ex;}}/// <summary>/// 获取html/// </summary>/// <param name="getUrl"></param>/// <param name="cookieContainer"></param>/// <param name="header"></param>/// <returns></returns>public static string GetHtml(string getUrl, CookieContainer cookieContainer, HttpHeader header){Thread.Sleep(1000);HttpWebRequest httpWebRequest = null;HttpWebResponse httpWebResponse = null;try{httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(getUrl);httpWebRequest.CookieContainer = cookieContainer;httpWebRequest.ContentType = header.contentType;httpWebRequest.ServicePoint.ConnectionLimit = header.maxTry;httpWebRequest.Referer = getUrl;httpWebRequest.Accept = header.accept;httpWebRequest.UserAgent = header.userAgent;httpWebRequest.Method = "GET";httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();Stream responseStream = httpWebResponse.GetResponseStream();StreamReader streamReader = new StreamReader(responseStream, Encoding.UTF8);string html = streamReader.ReadToEnd();streamReader.Close();responseStream.Close();httpWebRequest.Abort();httpWebResponse.Close();return html;}catch (Exception e){if (httpWebRequest != null) httpWebRequest.Abort();if (httpWebResponse != null) httpWebResponse.Close();return string.Empty;}}
}public class HttpHeader
{public string contentType { get; set; }public string accept { get; set; }public string userAgent { get; set; }public string method { get; set; }public int maxTry { get; set; }
}

}
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　　这样获取到的就是登录之后的页面了。

三、模拟表单提交
　　再来一个例子，运用HttpWebRequest来模拟表单的提交，先新建一个MVC项目，里面只有这些代码：

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[HttpPost]
public ActionResult Index(string userName,string userPassword)
{
string str = “你提交过来的用户名是:” + userName + ",密码是: " + userPassword;
Response.Write(str);
return View();
}
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　　然后启动该项目，再新建另外一个项目,用于模拟提交表单，然后注意路径填写的是刚才建的那个MVC项目。

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static void Main(string[] args)
{
HttpWebRequest request = null;
HttpWebResponse response = null;
CookieContainer cc = new CookieContainer();
request = (HttpWebRequest)WebRequest.Create(“http://localhost:2539/”);
request.Method = “POST”;
request.ContentType = “application/x-www-form-urlencoded”;
request.UserAgent = “Mozilla/5.0 (Windows NT 6.1; rv:19.0) Gecko/20100101 Firefox/19.0”;

        string requestForm = "userName=1693372175&userPassword=123456";     //拼接Form表单里的信息byte[] postdatabyte = Encoding.UTF8.GetBytes(requestForm);request.ContentLength = postdatabyte.Length;request.AllowAutoRedirect = false;request.CookieContainer = cc;request.KeepAlive = true;Stream stream;stream = request.GetRequestStream();stream.Write(postdatabyte, 0, postdatabyte.Length); //设置请求主体的内容stream.Close();//接收响应response = (HttpWebResponse)request.GetResponse();Console.WriteLine();Stream stream1 = response.GetResponseStream();StreamReader sr = new StreamReader(stream1);Console.WriteLine(sr.ReadToEnd());Console.ReadKey();}

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　　输出结果如下所示：

四、模拟上传
　　血的教训，注意路径不能写错，否则在对流进行操作时，Write，就会报错：

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(“http://localhost:9170/upload/test”);
　　客户端：

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class Program
{
/**
* 如果要在客户端向服务器上传文件，我们就必须模拟一个POST multipart/form-data类型的请求
* Content-Type必须是multipart/form-data。
* 以multipart/form-data编码的POST请求格式与application/x-www-form-urlencoded完全不同
* multipart/form-data需要首先在HTTP请求头设置一个分隔符,例如7d4a6d158c9：
* 我们模拟的提交要设定 content-type不同于非含附件的post时候的content-type
* 这里需要： (“Content-Type”, “multipart/form-data; boundary=ABCD”);
* 然后，将每个字段用“–7d4a6d158c9”分隔，最后一个“–7d4a6d158c9–”表示结束。
* 例如，要上传一个title字段"Today"和一个文件C:\\1.txt，HTTP正文如下：
*
* --7d4a6d158c9
* Content-Disposition: form-data; name=“title”
* \\r\\n\\r\\n
* Today
* --7d4a6d158c9
* Content-Disposition: form-data; name=“1.txt”; filename=“C:\\1.txt”
* Content-Type: text/plain
* 如果是图片Content-Type: application/octet-stream
* \\r\\n\\r\\n
* <这里是1.txt文件的内容>
* --7d4a6d158c9
* \\r\\n
* 请注意，每一行都必须以\\r\\n结束value前面必须有2个\\r\\n，包括最后一行。
*/
static void Main(string[] args)
{
string boundary = “----------” + DateTime.Now.Ticks.ToString(“x”);//元素分割标记
StringBuilder sb = new StringBuilder();
sb.Append(“–” + boundary);
sb.Append(“\\r\\n”);
sb.Append(“Content-Disposition: form-data; name=“file1”; filename=“D:\\upload.xml” + “””);
sb.Append(“\\r\\n”);
sb.Append(“Content-Type: application/octet-stream”);
sb.Append(“\\r\\n”);
sb.Append(“\\r\\n”);//value前面必须有2个换行

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://localhost:9170/upload/test");request.ContentType = "multipart/form-data; boundary=" + boundary;//其他地方的boundary要比这里多--  request.Method = "POST";FileStream fileStream = new FileStream(@"D:\\123.xml", FileMode.OpenOrCreate, FileAccess.Read);byte[] postHeaderBytes = Encoding.UTF8.GetBytes(sb.ToString());byte[] boundaryBytes = Encoding.ASCII.GetBytes("\\r\\n--" + boundary + "\\r\\n");//http请求总长度  request.ContentLength = postHeaderBytes.Length + fileStream.Length + boundaryBytes.Length;Stream requestStream = request.GetRequestStream(); requestStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);byte[] buffer = new Byte[checked((uint)Math.Min(4096, (int)fileStream.Length))];int bytesRead = 0;while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0){requestStream.Write(buffer, 0, bytesRead);}fileStream.Dispose();requestStream.Write(boundaryBytes, 0, boundaryBytes.Length);WebResponse webResponse2 = request.GetResponse();Stream htmlStream = webResponse2.GetResponseStream();string HTML = GetHtml(htmlStream, "UTF-8");Console.WriteLine(HTML);htmlStream.Dispose();}

}
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　　测试服务器端地址：

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public ActionResult Test()
{
HttpRequest request = System.Web.HttpContext.Current.Request;
HttpFileCollection FileCollect = request.Files;
if (FileCollect.Count > 0) //如果集合的数量大于0
{
foreach (string str in FileCollect)
{
HttpPostedFile FileSave = FileCollect[str]; //用key获取单个文件对象HttpPostedFile
string imgName = DateTime.Now.ToString(“yyyyMMddhhmmss”);
string AbsolutePath = FileSave.FileName;
FileSave.SaveAs(AbsolutePath); //将上传的东西保存
}
}
return Content(“键值对数目：” + FileCollect.Count);
}