/// <summary>
/// 获取给定URL的内容,失败时返回NULL
/// </summary>
/// <param name="url">Url实例</param>
/// <returns>Content实例或NULL</returns>
private Content GetContent(Url url)
{
if (null == url)
{
return(null);
}
string s = url.GetUrl();
HttpWebRequest request = WebRequest.Create(s) as HttpWebRequest;
this.settings.PrepareRequest(request);
//带参数的POST请求
if (url.HttpMethod == "POST" && null != url.AppendParams && url.AppendParams.Count > 0)
{
request.Method = "POST";
request.ContentType = String.Format("application/x-www-form-urlencoded;charset={0}", this.settings.RequestEncoding.WebName);
byte[] data = GetRequestData(url.AppendParams, this.settings.RequestEncoding);
request.ContentLength = data.Length;
using (Stream reqStream = request.GetRequestStream())
{
reqStream.Write(data, 0, data.Length);
}
this.runtime.bytesSent += data.Length;
}
HttpWebResponse response = null;
Content content = null;
try
{
response = request.GetResponse() as HttpWebResponse;
}
catch (WebException we)
{
if (Environment.UserInteractive)
{
Console.WriteLine(String.Format("WebException状态:{0}, 消息:{1}", we.Status, we.Message));
}
url.SetError(we.Message);
if (we.Status == WebExceptionStatus.Timeout || we.Status == WebExceptionStatus.ReceiveFailure || we.Status == WebExceptionStatus.UnknownError)
{
//普通或者慢速模式下,进行失败重试
if (((int)this.settings.SpeedMode) >= ((int)SpiderSetting.SpeedModes.Normal) && url.MaxTryTimes > 0 && url.CanTryAgain)
{
url.AddTryTime();
this.urlQueue.Add(url);
}
}
return(null);
}
catch (Exception e)
{
if (Environment.UserInteractive)
{
this.WriteLog(e.Message);
}
return(null);
}
finally
{
this.runtime.urlTotal++;
}
if (null == response)
{
return(null);
}
url.ClearError();
using (Stream stream = response.GetResponseStream())
{
RequestContext context = new RequestContext(this.settings, url, response);
content = Content.Create(context);
if (null != content)
{
content.Read(stream);
this.runtime.bytesLoaded += content.ContentLength;
}
}
return(content);
}
