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/*
* Copyright (c) Contributors, http://opensimulator.org/
* See CONTRIBUTORS.TXT for a full list of copyright holders.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
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* notice, this list of conditions and the following disclaimer.
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* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
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* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Reflection;
using System.Text;
using System.Threading;
using System.Web;
using log4net;
namespace OpenSim.Framework.Communications
{
/// <summary>
/// Implementation of a generic REST client
/// </summary>
/// <remarks>
/// This class is a generic implementation of a REST (Representational State Transfer) web service. This
/// class is designed to execute both synchronously and asynchronously.
///
/// Internally the implementation works as a two stage asynchronous web-client.
/// When the request is initiated, RestClient will query asynchronously for for a web-response,
/// sleeping until the initial response is returned by the server. Once the initial response is retrieved
/// the second stage of asynchronous requests will be triggered, in an attempt to read of the response
/// object into a memorystream as a sequence of asynchronous reads.
///
/// The asynchronisity of RestClient is designed to move as much processing into the back-ground, allowing
/// other threads to execute, while it waits for a response from the web-service. RestClient itself can be
/// invoked by the caller in either synchronous mode or asynchronous modes.
/// </remarks>
public class RestClient
{
private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
// private string realuri;
#region member variables
/// <summary>
/// The base Uri of the web-service e.g. http://www.google.com
/// </summary>
private string _url;
/// <summary>
/// Path elements of the query
/// </summary>
private List<string> _pathElements = new List<string>();
/// <summary>
/// Parameter elements of the query, e.g. min=34
/// </summary>
private Dictionary<string, string> _parameterElements = new Dictionary<string, string>();
/// <summary>
/// Request method. E.g. GET, POST, PUT or DELETE
/// </summary>
private string _method;
/// <summary>
/// Temporary buffer used to store bytes temporarily as they come in from the server
/// </summary>
private byte[] _readbuf;
/// <summary>
/// MemoryStream representing the resultiong resource
/// </summary>
private Stream _resource;
/// <summary>
/// WebRequest object, held as a member variable
/// </summary>
private HttpWebRequest _request;
/// <summary>
/// WebResponse object, held as a member variable, so we can close it
/// </summary>
private HttpWebResponse _response;
/// <summary>
/// This flag will help block the main synchroneous method, in case we run in synchroneous mode
/// </summary>
//public static ManualResetEvent _allDone = new ManualResetEvent(false);
/// <summary>
/// Default time out period
/// </summary>
//private const int DefaultTimeout = 10*1000; // 10 seconds timeout
/// <summary>
/// Default Buffer size of a block requested from the web-server
/// </summary>
private const int BufferSize = 4096; // Read blocks of 4 KB.
/// <summary>
/// if an exception occours during async processing, we need to save it, so it can be
/// rethrown on the primary thread;
/// </summary>
private Exception _asyncException;
#endregion member variables
#region constructors
/// <summary>
/// Instantiate a new RestClient
/// </summary>
/// <param name="url">Web-service to query, e.g. http://osgrid.org:8003</param>
public RestClient(string url)
{
_url = url;
_readbuf = new byte[BufferSize];
_resource = new MemoryStream();
_request = null;
_response = null;
_lock = new object();
}
private object _lock;
#endregion constructors
/// <summary>
/// Add a path element to the query, e.g. assets
/// </summary>
/// <param name="element">path entry</param>
public void AddResourcePath(string element)
{
if (isSlashed(element))
_pathElements.Add(element.Substring(0, element.Length - 1));
else
_pathElements.Add(element);
}
/// <summary>
/// Add a query parameter to the Url
/// </summary>
/// <param name="name">Name of the parameter, e.g. min</param>
/// <param name="value">Value of the parameter, e.g. 42</param>
public void AddQueryParameter(string name, string value)
{
try
{
_parameterElements.Add(HttpUtility.UrlEncode(name), HttpUtility.UrlEncode(value));
}
catch (ArgumentException)
{
m_log.Error("[REST]: Query parameter " + name + " is already added.");
}
catch (Exception e)
{
m_log.Error("[REST]: An exception was raised adding query parameter to dictionary. Exception: {0}",e);
}
}
/// <summary>
/// Add a query parameter to the Url
/// </summary>
/// <param name="name">Name of the parameter, e.g. min</param>
public void AddQueryParameter(string name)
{
try
{
_parameterElements.Add(HttpUtility.UrlEncode(name), null);
}
catch (ArgumentException)
{
m_log.Error("[REST]: Query parameter " + name + " is already added.");
}
catch (Exception e)
{
m_log.Error("[REST]: An exception was raised adding query parameter to dictionary. Exception: {0}",e);
}
}
/// <summary>
/// Web-Request method, e.g. GET, PUT, POST, DELETE
/// </summary>
public string RequestMethod
{
get { return _method; }
set { _method = value; }
}
/// <summary>
/// True if string contains a trailing slash '/'
/// </summary>
/// <param name="s">string to be examined</param>
/// <returns>true if slash is present</returns>
private static bool isSlashed(string s)
{
return s.Substring(s.Length - 1, 1) == "/";
}
/// <summary>
/// Build a Uri based on the initial Url, path elements and parameters
/// </summary>
/// <returns>fully constructed Uri</returns>
private Uri buildUri()
{
StringBuilder sb = new StringBuilder();
sb.Append(_url);
foreach (string e in _pathElements)
{
sb.Append("/");
sb.Append(e);
}
bool firstElement = true;
foreach (KeyValuePair<string, string> kv in _parameterElements)
{
if (firstElement)
{
sb.Append("?");
firstElement = false;
}
else
sb.Append("&");
sb.Append(kv.Key);
if (!string.IsNullOrEmpty(kv.Value))
{
sb.Append("=");
sb.Append(kv.Value);
}
}
// realuri = sb.ToString();
//m_log.InfoFormat("[REST CLIENT]: RestURL: {0}", realuri);
return new Uri(sb.ToString());
}
#region Async communications with server
/// <summary>
/// Async method, invoked when a block of data has been received from the service
/// </summary>
/// <param name="ar"></param>
private void StreamIsReadyDelegate(IAsyncResult ar)
{
try
{
Stream s = (Stream) ar.AsyncState;
int read = s.EndRead(ar);
if (read > 0)
{
_resource.Write(_readbuf, 0, read);
// IAsyncResult asynchronousResult =
// s.BeginRead(_readbuf, 0, BufferSize, new AsyncCallback(StreamIsReadyDelegate), s);
s.BeginRead(_readbuf, 0, BufferSize, new AsyncCallback(StreamIsReadyDelegate), s);
// TODO! Implement timeout, without killing the server
//ThreadPool.RegisterWaitForSingleObject(asynchronousResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true);
}
else
{
s.Close();
//_allDone.Set();
}
}
catch (Exception e)
{
//_allDone.Set();
_asyncException = e;
}
}
#endregion Async communications with server
/// <summary>
/// Perform a synchronous request
/// </summary>
public Stream Request()
{
lock (_lock)
{
_request = (HttpWebRequest) WebRequest.Create(buildUri());
_request.KeepAlive = false;
_request.ContentType = "application/xml";
_request.Timeout = 200000;
_request.Method = RequestMethod;
_asyncException = null;
// IAsyncResult responseAsyncResult = _request.BeginGetResponse(new AsyncCallback(ResponseIsReadyDelegate), _request);
try
{
_response = (HttpWebResponse) _request.GetResponse();
}
catch (WebException e)
{
HttpWebResponse errorResponse = e.Response as HttpWebResponse;
if (null != errorResponse && HttpStatusCode.NotFound == errorResponse.StatusCode)
{
m_log.Warn("[REST CLIENT] Resource not found (404)");
}
else
{
m_log.Error("[REST CLIENT] Error fetching resource from server " + _request.Address.ToString());
m_log.Debug(e.ToString());
}
return null;
}
Stream src = _response.GetResponseStream();
int length = src.Read(_readbuf, 0, BufferSize);
while (length > 0)
{
_resource.Write(_readbuf, 0, length);
length = src.Read(_readbuf, 0, BufferSize);
}
// TODO! Implement timeout, without killing the server
// this line implements the timeout, if there is a timeout, the callback fires and the request becomes aborted
//ThreadPool.RegisterWaitForSingleObject(responseAsyncResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true);
// _allDone.WaitOne();
if (_response != null)
_response.Close();
if (_asyncException != null)
throw _asyncException;
if (_resource != null)
{
_resource.Flush();
_resource.Seek(0, SeekOrigin.Begin);
}
return _resource;
}
}
public Stream Request(Stream src)
{
_request = (HttpWebRequest) WebRequest.Create(buildUri());
_request.KeepAlive = false;
_request.ContentType = "application/xml";
_request.Timeout = 900000;
_request.Method = RequestMethod;
_asyncException = null;
_request.ContentLength = src.Length;
m_log.InfoFormat("[REST]: Request Length {0}", _request.ContentLength);
m_log.InfoFormat("[REST]: Sending Web Request {0}", buildUri());
src.Seek(0, SeekOrigin.Begin);
m_log.Info("[REST]: Seek is ok");
Stream dst = _request.GetRequestStream();
m_log.Info("[REST]: GetRequestStream is ok");
byte[] buf = new byte[1024];
int length = src.Read(buf, 0, 1024);
m_log.Info("[REST]: First Read is ok");
while (length > 0)
{
dst.Write(buf, 0, length);
length = src.Read(buf, 0, 1024);
}
_response = (HttpWebResponse) _request.GetResponse();
// IAsyncResult responseAsyncResult = _request.BeginGetResponse(new AsyncCallback(ResponseIsReadyDelegate), _request);
// TODO! Implement timeout, without killing the server
// this line implements the timeout, if there is a timeout, the callback fires and the request becomes aborted
//ThreadPool.RegisterWaitForSingleObject(responseAsyncResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true);
return null;
}
#region Async Invocation
public IAsyncResult BeginRequest(AsyncCallback callback, object state)
{
/// <summary>
/// In case, we are invoked asynchroneously this object will keep track of the state
/// </summary>
AsyncResult<Stream> ar = new AsyncResult<Stream>(callback, state);
Util.FireAndForget(RequestHelper, ar);
return ar;
}
public Stream EndRequest(IAsyncResult asyncResult)
{
AsyncResult<Stream> ar = (AsyncResult<Stream>) asyncResult;
// Wait for operation to complete, then return result or
// throw exception
return ar.EndInvoke();
}
private void RequestHelper(Object asyncResult)
{
// We know that it's really an AsyncResult<DateTime> object
AsyncResult<Stream> ar = (AsyncResult<Stream>) asyncResult;
try
{
// Perform the operation; if sucessful set the result
Stream s = Request();
ar.SetAsCompleted(s, false);
}
catch (Exception e)
{
// If operation fails, set the exception
ar.HandleException(e, false);
}
}
#endregion Async Invocation
}
}