HttpWebRequest使用注意（发生阻塞的解决办法）

墨蓝 2022-03-29 03:16 225阅读 0赞

HttpWebResponse myResponse = null;
                Stream reqStream = null; 
                Stream resStream = null;
    
                try
                {
                    byte[] data = System.Text.Encoding.Default.GetBytes(param);
    
                    myRequest = (HttpWebRequest)WebRequest.Create(url);
                    myRequest.Method = "POST";
                    myRequest.KeepAlive = true;
                    myRequest.ContentType = "application/octet-stream";
                    myRequest.ContentLength = data.Length;
                    reqStream = myRequest.GetRequestStream();
                    reqStream.Write(data, 0, data.Length);
                    reqStream.Close();
    
                    myResponse = (HttpWebResponse)myRequest.GetResponse();
                    resStream = myResponse.GetResponseStream();
                    data = new byte[512];
                    int count = 0;
                    UIFactory.zZRK_MODIForm.memStream = new MemoryStream();
                    while ((count = resStream.Read(data, 0, data.Length)) > 0)
                    {
                        UIFactory.zZRK_MODIForm.memStream.Write(data, 0, count);
                    }
                    resStream.Close();
                    
                }
                catch
                {
                }
                finally
                {
                    if (resStream != null)
                    {
                        resStream.Close();
                    }
                    if (reqStream != null)
                    {
                        reqStream.Close();
                    }
                    if (myResponse != null)
                    {
                        myResponse.Close();
                    }
                }

大家看下这段程序，有问题吗？乍一看，好像没有什么问题，所有的流都释放了，Response也释放了。。不过如果你写个循环无限次发起请求，你会发现，运行不了几次就阻塞了。为什么呢？大家看下面的代码

HttpWebRequest myRequest = null;
                HttpWebResponse myResponse = null;
                Stream reqStream = null; 
                Stream resStream = null;
    
                try
                {
                    byte[] data = System.Text.Encoding.Default.GetBytes(param);
    
                    //想服务器端发送请求，获取照片信息
                    myRequest = (HttpWebRequest)WebRequest.Create(url);
                    myRequest.Method = "POST";
                    myRequest.KeepAlive = true;
                    myRequest.ContentType = "application/octet-stream";
                    myRequest.ContentLength = data.Length;
                    reqStream = myRequest.GetRequestStream();
                    reqStream.Write(data, 0, data.Length);
                    reqStream.Close();
    
                    myResponse = (HttpWebResponse)myRequest.GetResponse();
                    resStream = myResponse.GetResponseStream();
                    data = new byte[512];
                    int count = 0;
                    UIFactory.zZRK_MODIForm.memStream = new MemoryStream();
                    while ((count = resStream.Read(data, 0, data.Length)) > 0)
                    {
                        UIFactory.zZRK_MODIForm.memStream.Write(data, 0, count);
                    }
                    resStream.Close();
                    
                }
                catch
                {
                }
                finally
                {
                    if (resStream != null)
                    {
                        resStream.Close();
                    }
                    if (reqStream != null)
                    {
                        reqStream.Close();
                    }
                    if (myResponse != null)
                    {
                        myResponse.Close();
                    }
                    if (myRequest != null)
                    {
                        myRequest.Abort();
                    }
                }

多了些什么？多了这个

if (myRequest != null)
    {
    myRequest.Abort();
    }

其实很多时候释放了Stream和Response还不够，客户端的Request还是在保持着，需要等垃圾回收器来回收，所以一般很容易阻塞，导致请求发送不出去。加上这个就是让HttpWebRequest实例在不需要的时候及时释放资源。这样可以重复使用而不会阻塞。