C# 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：

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();
    }
}    

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。

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; }
    }
}

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：

[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();
        }
复制代码

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。

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();
        }

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");

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" 
         * 

 
         * 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 
         * 

 
         * <这里是1.txt文件的内容> 
         * --7d4a6d158c9 
         * 
 
         * 请注意，每一行都必须以
结束value前面必须有2个
，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("
");
            sb.Append("Content-Disposition: form-data; name="file1"; filename="D:\upload.xml" + """);
            sb.Append("
");
            sb.Append("Content-Type: application/octet-stream");
            sb.Append("
");
            sb.Append("
");//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("
--" + boundary + "
");
            //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();
        }
　　}

测试服务器端地址：

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);
        }

转：

逆心

HttpWebRequest类