package org.jboss.resteasy.client.jaxrs.engines;

import java.io.ByteArrayOutputStream;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.nio.ByteBuffer;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.function.Supplier;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.SSLContext;
import javax.ws.rs.ProcessingException;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.client.Invocation;
import javax.ws.rs.client.InvocationCallback;
import javax.ws.rs.client.ResponseProcessingException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.core.Response;

import org.apache.commons.io.IOUtils;
import org.apache.http.ContentTooLongException;
import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpEntityEnclosingRequest;
import org.apache.http.HttpException;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpRequestBase;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.concurrent.BasicFuture;
import org.apache.http.concurrent.FutureCallback;
import org.apache.http.entity.ByteArrayEntity;
import org.apache.http.entity.ContentType;
import org.apache.http.impl.nio.client.CloseableHttpAsyncClient;
import org.apache.http.message.BasicHeader;
import org.apache.http.nio.ContentDecoder;
import org.apache.http.nio.IOControl;
import org.apache.http.nio.client.methods.HttpAsyncMethods;
import org.apache.http.nio.entity.ContentInputStream;
import org.apache.http.nio.protocol.AbstractAsyncResponseConsumer;
import org.apache.http.nio.protocol.HttpAsyncRequestProducer;
import org.apache.http.nio.protocol.HttpAsyncResponseConsumer;
import org.apache.http.nio.util.HeapByteBufferAllocator;
import org.apache.http.nio.util.SharedInputBuffer;
import org.apache.http.nio.util.SimpleInputBuffer;
import org.apache.http.protocol.HTTP;
import org.apache.http.protocol.HttpContext;
import org.jboss.resteasy.client.jaxrs.i18n.LogMessages;
import org.jboss.resteasy.client.jaxrs.internal.ClientConfiguration;
import org.jboss.resteasy.client.jaxrs.internal.ClientInvocation;
import org.jboss.resteasy.client.jaxrs.internal.ClientResponse;
import org.jboss.resteasy.client.jaxrs.internal.FinalizedClientResponse;
import org.jboss.resteasy.tracing.RESTEasyTracingLogger;
import org.jboss.resteasy.util.CaseInsensitiveMap;

AsyncClientHttpEngine using apache http components HttpAsyncClient 4.

Some words of caution: 

Asynchronous IO means non-blocking IO utilizing few threads, typically at most as much threads as number of cores.
As such, performance may profit from fewer thread switches and less memory usage due to fewer thread-stacks. But doing
synchronous, blocking IO (the invoke-methods not returning a future) may suffer, because the data has to be transferred
piecewiese to/from the io-threads.
Request-Entities are fully buffered in memory, thus this engine is unsuitable for very large uploads.
Response-Entities are buffered in memory, except if requesting a Response, InputStream or Reader as Result. Thus
for large downloads or COMET one of these three return types must be requested, but there may be a performance penalty
because the response-body is transferred piecewise from the io-threads. When using InvocationCallbacks, the response is
always fully buffered in memory.
InvocationCallbacks are called from within the io-threads and thus must not block or else the application may
slow down to a halt. Reading the response is safe (because the response is buffered in memory), as are other async
(and in-memory) Client-invocations (the submit-calls returning a future not containing Response, InputStream or Reader).
Again, there must be no blocking IO inside InvocationCallback! (If you are wondering why not to allow blocking calls by
wrapping InvocationCallbacks in extra threads: Because then the main advantage of async IO, less threading, is lost.)
InvocationCallbacks may be called seemingly "after" the future-object returns. Thus, responses should be handled
solely in the InvocationCallback.
InvocationCallbacks will see the same result as the future-object and vice versa. Thus, if the invocationcallback
throws an exception, the future-object will not see it. Another reason to handle responses only in the InvocationCallback.


Author:
Markus Kull/**
 * AsyncClientHttpEngine using apache http components HttpAsyncClient 4.<p>
 *
 * Some words of caution: <ul>
 * <li>Asynchronous IO means non-blocking IO utilizing few threads, typically at most as much threads as number of cores.
 * As such, performance may profit from fewer thread switches and less memory usage due to fewer thread-stacks. But doing
 * synchronous, blocking IO (the invoke-methods not returning a future) may suffer, because the data has to be transferred
 * piecewiese to/from the io-threads.</li>
 * <li>Request-Entities are fully buffered in memory, thus this engine is unsuitable for very large uploads.</li>
 * <li>Response-Entities are buffered in memory, except if requesting a Response, InputStream or Reader as Result. Thus
 * for large downloads or COMET one of these three return types must be requested, but there may be a performance penalty
 * because the response-body is transferred piecewise from the io-threads. When using InvocationCallbacks, the response is
 * always fully buffered in memory.</li>
 * <li>InvocationCallbacks are called from within the io-threads and thus must not block or else the application may
 * slow down to a halt. Reading the response is safe (because the response is buffered in memory), as are other async
 * (and in-memory) Client-invocations (the submit-calls returning a future not containing Response, InputStream or Reader).
 * Again, there must be no blocking IO inside InvocationCallback! (If you are wondering why not to allow blocking calls by
 * wrapping InvocationCallbacks in extra threads: Because then the main advantage of async IO, less threading, is lost.)
 * <li>InvocationCallbacks may be called seemingly "after" the future-object returns. Thus, responses should be handled
 * solely in the InvocationCallback.</li>
 * <li>InvocationCallbacks will see the same result as the future-object and vice versa. Thus, if the invocationcallback
 * throws an exception, the future-object will not see it. Another reason to handle responses only in the InvocationCallback.
 * </li>
 * </ul>
 * @author Markus Kull
 */
public class ApacheHttpAsyncClient4Engine implements AsyncClientHttpEngine, Closeable
{
   protected final CloseableHttpAsyncClient client;
   protected final boolean closeHttpClient;

   public ApacheHttpAsyncClient4Engine(final CloseableHttpAsyncClient client, final boolean closeHttpClient)
   {
      if (client == null) throw new NullPointerException("client");
      this.client = client;
      this.closeHttpClient = closeHttpClient;
      if (closeHttpClient && !client.isRunning()) {
         client.start();
      }
   }

   @Override
   public void close()
   {
      if (closeHttpClient)
      {
         IOUtils.closeQuietly(client);
      }
   }

   @Override
   public SSLContext getSslContext()
   {
      throw new UnsupportedOperationException();
   }

   @Override
   public HostnameVerifier getHostnameVerifier()
   {
      throw new UnsupportedOperationException();
   }

   @Override
   public Response invoke(Invocation request)
   {
      // Doing blocking requests with an async httpclient is quite useless.
      // But it is better to use the same httpclient in any case just for sharing+configuring only one connectionpool.
      Future<ClientResponse> future = submit((ClientInvocation)request, false, null, new ResultExtractor<ClientResponse>() {
         @Override
         public ClientResponse extractResult(ClientResponse response)
         {
            return response;
         }
      });
      try
      {
         return future.get();
      }
      catch (InterruptedException e)
      {
         future.cancel(true);
         throw clientException(e, null);
      }
      catch (ExecutionException e)
      {
         throw clientException(e.getCause(), null);
      }
   }

   @Override
   public <T> Future<T> submit(
      ClientInvocation request, boolean buffered, InvocationCallback<T> callback, ResultExtractor<T> extractor)
   {
      HttpUriRequest httpRequest = buildHttpRequest(request);

      if (buffered)
      {
         // Request+Response fully buffered in memory. Optional callback is called inside io-thread after response-body and
         // after the returned future is signaled to be completed.
         //
         // This differs to Resteasy 3.0.8 and earlier (which called the callback before the future completed) due to the
         // following reasons:
         //   * ApacheHttpcomponents BasicFuture, guavas ListenableFuture and also jersey calls the callback after completing
         //     the future. The earlier Resteasy-behaviour may be more "safe" but any users switching from resteasy to another
         //     jax-rs implementation may encounter a nasty surprise.
         //   * ensure the result returned by the future is the same given to the callback.
         //   * As good practice, the result should only be handled in one place (future OR callback, not both)
         //   * Invocation-javadoc says "the underlying response instance will be automatically closed" seemingly implying
         //     the future-response is unusable (bc. closed) together with a callback
         // Of course the one big drawback is that exceptions inside the callback are not visible to the application,
         // but callbacks are mostly treated as fire-and-forget, meaning their result is not checked anyway.
         HttpAsyncRequestProducer requestProducer = HttpAsyncMethods.create(httpRequest);
         HttpAsyncResponseConsumer<T> responseConsumer = new BufferingResponseConsumer<T>(request, extractor);
         FutureCallback<T> httpCallback = callback != null ? new CallbackAdapter<T>(callback) : null;

         return client.execute(requestProducer, responseConsumer, httpCallback);
      }
      else
      {
         // unbuffered: Future returns immediately after headers. Reading the response-stream blocks, but one may check
         // InputStream#available() to prevent blocking.

         // would be easy to call an InvocationCallback after response-BODY, but cant see any usecase for it.
         if (callback != null) throw new IllegalArgumentException("unbuffered InvocationCallback is not supported");

         HttpAsyncRequestProducer requestProducer = HttpAsyncMethods.create(httpRequest);
         StreamingResponseConsumer<T> responseConsumer = new StreamingResponseConsumer<T>(request, extractor);

         Future<T> httpFuture = client.execute(requestProducer, responseConsumer, null);
         return responseConsumer.future(httpFuture);
      }
   }

   @Override
   public <T> CompletableFuture<T> submit(ClientInvocation request,
         boolean buffered,
         ResultExtractor<T> extractor,
         ExecutorService executorService) {
      if (buffered) {
         final CompletableFuture<T> cf = new CompletableFuture<>();
         final InvocationCallback<T> callback = new InvocationCallback<T>()
         {
            @Override
            public void completed(T response)
            {
               cf.complete(response);
            }

            @Override
            public void failed(Throwable throwable)
            {
               cf.completeExceptionally(throwable);
            }
         };
         submit(request, buffered, callback, extractor);
         return cf;
      } else {
         final Supplier<T> supplier = () -> {
            try {
               return submit(request, buffered, null, extractor).get();
            } catch (InterruptedException|ExecutionException e) {
               throw new RuntimeException(e);
            }
         };

         if(executorService == null)
         {
            return CompletableFuture.supplyAsync(supplier);
         }
         else
         {
            return CompletableFuture.supplyAsync(supplier, executorService);
         }
      }
   }


   
ResponseConsumer which transfers the response piecewise from the io-thread to the blocking handler-thread. future(Future) returns a Future which completes immediately after receiving the response-headers but reading the response-inputstream blocks until data is available. /**
    * ResponseConsumer which transfers the response piecewise from the io-thread to the blocking handler-thread.
    * {@link #future(Future)} returns a Future which completes immediately after receiving the response-headers
    * but reading the response-inputstream blocks until data is available.
    */
   private static class StreamingResponseConsumer<T> implements HttpAsyncResponseConsumer<T>
   {
      @SuppressWarnings("serial")
      private static final IOException unallowedBlockingReadException = new IOException("blocking reads inside an async io-handler are not allowed") {
         public synchronized Throwable fillInStackTrace() {
            //do nothing and return
            return this;
         }
      };

      private ClientConfiguration configuration;
      private Map<String, Object> properties;
      private ResultExtractor<T> extractor;

      private ResultFuture<T> future;
      private SharedInputStream sharedStream;

      private boolean hasResult;
      private volatile T result;
      private volatile Exception exception;
      private volatile boolean completed;

      StreamingResponseConsumer(final ClientInvocation request, final ResultExtractor<T> extractor)
      {
         this.configuration = request.getClientConfiguration();
         this.properties = request.getMutableProperties();
         this.extractor = extractor;
      }

      private void releaseResources()
      {
         this.configuration = null;
         this.properties = null;
         this.extractor = null;

         this.future = null;
         this.sharedStream = null;
      }

      public synchronized Future<T> future(Future<T> httpFuture)
      {
         if (completed)
         {  // already failed or fully buffered
            return httpFuture;
         }
         future = new ResultFuture<T>(httpFuture);
         future.copyHttpFutureResult();
         if (!future.isDone() && hasResult)
         { // response(-headers) is available, but not yet the full response-stream. Return immediately the result
            future.completed(getResult());
         }
         return future;
      }

      @Override
      public synchronized void responseReceived(HttpResponse httpResponse) throws IOException, HttpException
      {
         SharedInputStream sharedStream = null;
         ConnectionResponse clientResponse = null;
         T result = null;
         Exception exception = null;

         boolean success = false;
         try {
            clientResponse = new ConnectionResponse(configuration, properties);
            copyResponse(httpResponse, clientResponse);
            final HttpEntity entity = httpResponse.getEntity();
            if (entity != null)
            {
               sharedStream = new SharedInputStream(new SharedInputBuffer(16 * 1024));
               // one could also set the stream after extracting the response, but this would prevent wrapping the stream
               clientResponse.setConnection(sharedStream);
               sharedStream.setException(unallowedBlockingReadException);
               result = extractor.extractResult(clientResponse);
               sharedStream.setException(null);
            }
            else
            {
               result = extractor.extractResult(clientResponse);
            }
            success = true;
         }
         catch(Exception e)
         {
            exception = clientException(e, clientResponse);
         }
         finally
         {
            if (success)
            {
               this.sharedStream = sharedStream;
               this.result = result;
               this.hasResult = true;
               if (future != null) future.completed(result);
            }
            else
            {
               this.exception = exception;
               completed = true;
               if (future != null) future.failed(exception);
               releaseResources();
            }
         }
      }

      @Override
      public synchronized void consumeContent(ContentDecoder decoder, IOControl ioctrl) throws IOException
      {
         if (sharedStream != null) sharedStream.consumeContent(decoder, ioctrl);
      }

      @Override
      public synchronized void responseCompleted(HttpContext context)
      {
         this.completed = true;
         try
         {
            if (sharedStream != null)
            {  // only needed in case of empty response body (=null ioctrl)
               sharedStream.consumeContent(EndOfStream.INSTANCE, null);
            }
         }
         catch (IOException ioe)
         { // cannot happen
            throw new RuntimeException(ioe);
         }
         finally
         {
            releaseResources();
         }
      }

      @Override
      public Exception getException()
      {
         return exception;
      }

      @Override
      public T getResult()
      {
         return result;
      }

      @Override
      public boolean isDone()
      {  // cancels in case of closing the SharedInputStream
         return completed;
      }

      @Override
      public synchronized void close()
      {
         completed = true;
         ResultFuture<T> future = this.future;
         if (future != null)
         {
            // if connect fails, then the httpclient just calls close() after setting its future, but never our failed().
            // so copy the httpFuture-result into our ResultFuture.
            future.copyHttpFutureResult();
            if (!future.isDone())
            { // doesnt happen?
               future.failed(clientException(new IOException("connect failed"), null));
            }
         }
         releaseResources();
      }

      @Override
      public synchronized void failed(Exception ex)
      {
         completed = true;
         if (future != null) future.failed(clientException(ex, null));
         if (sharedStream != null)
         {
            sharedStream.setException(ioException(ex));
            IOUtils.closeQuietly(sharedStream);
         }
         releaseResources();
      }

      @Override
      public synchronized boolean cancel()
      {
         completed = true;
         if (future != null) future.cancelledResult();
         if (sharedStream != null)
         {
            sharedStream.setException(new IOException("cancelled"));
            IOUtils.closeQuietly(sharedStream);
         }
         releaseResources();
         return true;
      }

      private static class ResultFuture<T> extends BasicFuture<T>
      {
         private final Future<T> httpFuture;

         ResultFuture(final Future<T> httpFuture)
         {
            super(null);
            this.httpFuture = httpFuture;
         }

         @Override
         public boolean cancel(boolean mayInterruptIfRunning)
         {
            boolean cancelled = super.cancel(mayInterruptIfRunning);
            httpFuture.cancel(mayInterruptIfRunning);
            return cancelled;
         }

         public void cancelledResult() {
            super.cancel(true);
         }

         public void copyHttpFutureResult()
         {
            if (!isDone() && httpFuture.isDone())
            {
               try
               {
                  completed(httpFuture.get());
               }
               catch(ExecutionException e)
               {
                  failed(clientException(e.getCause(), null));
               }
               catch (InterruptedException e)
               { // cant happen because already isDone
                  failed(e);
               }
            }
         }
      }

      private class SharedInputStream extends ContentInputStream {

         private final SharedInputBuffer sharedBuf;
         private volatile IOException ex;
         private volatile IOControl ioctrl;

         SharedInputStream(final SharedInputBuffer sharedBuf)
         {
            super(sharedBuf);
            this.sharedBuf = sharedBuf;
         }

         public void consumeContent(ContentDecoder decoder, IOControl ioctrl) throws IOException {
            if (ioctrl != null) this.ioctrl = ioctrl;
            sharedBuf.consumeContent(decoder, ioctrl);
         }

         @Override
         public void close() throws IOException
         {
            completed = true; // next isDone() cancels.

            // Workaround for deadlock: super.close() reads until no more data, but on cancellation no more data is
            // pushed to consumeContent, thus deadlock. Instead notify the reactor by ioctrl.requestInput
            sharedBuf.close(); // next reads will return EndOfStream. Also wakes up any waiting readers
            IOControl ioctrl = this.ioctrl;
            if (ioctrl != null) ioctrl.requestInput(); // notify reactor to check isDone()
            super.close(); // does basically nothing due to closed buf
         }

         @Override
         public int read(final byte[] b, final int off, final int len) throws IOException
         {
            throwIfError();
            return super.read(b, off, len);
         }

         @Override
         public int read(final byte[] b) throws IOException
         {
            throwIfError();
            return super.read(b, 0, b.length);
         }

         @Override
         public int read() throws IOException {
            throwIfError();
            return super.read();
         }

         private void throwIfError() throws IOException {
            IOException ex = this.ex;
            if (ex != null) {
               //create a new exception here to make it easy figuring out where the offending blocking IO comes from
               throw new IOException(ex);
            }
         }

         public void setException(IOException e) {
            this.ex = e;
         }
      }
   }

   
Buffers response fully in memory.
(Buffering is definitely easier to implement than streaming)
/**
    * Buffers response fully in memory.
    *
    * (Buffering is definitely easier to implement than streaming)
    */
   private static class BufferingResponseConsumer<T> extends AbstractAsyncResponseConsumer<T>
   {

      private ClientConfiguration configuration;
      private Map<String, Object> properties;
      private ResultExtractor<T> responseExtractor;
      private ConnectionResponse clientResponse;
      private SimpleInputBuffer buf;

      BufferingResponseConsumer(final ClientInvocation request, final ResultExtractor<T> responseExtractor)
      {
         this.configuration = request.getClientConfiguration();
         this.properties = request.getMutableProperties();
         this.responseExtractor = responseExtractor;
      }

      @Override
      protected void onResponseReceived(HttpResponse response) throws HttpException, IOException
      {
         ConnectionResponse clientResponse = new ConnectionResponse(configuration, properties);
         copyResponse(response, clientResponse);
         final HttpEntity entity = response.getEntity();
         if (entity != null)
         {
            long len = entity.getContentLength();
            if (len > Integer.MAX_VALUE)
            {
               throw new ContentTooLongException("Entity content is too long: " + len);
            }
            if (len < 0)
            {
               len = 4096;
            }
            this.buf = new SimpleInputBuffer((int) len, new HeapByteBufferAllocator());
         }
         this.clientResponse = clientResponse;
      }

      @Override
      protected void onEntityEnclosed(HttpEntity entity, ContentType contentType) throws IOException
      {
      }

      @Override
      protected void onContentReceived(ContentDecoder decoder, IOControl ioctrl) throws IOException
      {
         SimpleInputBuffer buf = this.buf;
         if (buf == null) throw new NullPointerException("Content Buffer");
         buf.consumeContent(decoder);
      }

      @Override
      protected T buildResult(HttpContext context) throws Exception
      {
         if (buf != null) clientResponse.setConnection(new ContentInputStream(buf));
         return responseExtractor.extractResult(clientResponse);
      }

      @Override
      protected void releaseResources()
      {
         this.configuration = null;
         this.properties = null;
         this.responseExtractor = null;
         this.clientResponse = null;
         this.buf = null;
      }
   }

   
Adapter from http-FutureCallback to InvocationCallback
/**
    * Adapter from http-FutureCallback<T> to InvocationCallback<T>
    */
   private static class CallbackAdapter<T> implements FutureCallback<T>
   {
      private final InvocationCallback<T> invocationCallback;

      CallbackAdapter(final InvocationCallback<T> invocationCallback)
      {
         this.invocationCallback = invocationCallback;
      }

      @Override
      public void cancelled()
      {
         invocationCallback.failed(new ProcessingException("cancelled"));
      }

      @Override
      public void completed(T response)
      {
         try
         {
            invocationCallback.completed(response);
         }
         catch (Throwable t)
         {
            LogMessages.LOGGER.exceptionIgnored(t);
         }
         finally
         {
            // just to promote proper callback usage, because HttpAsyncClient is responsible
            // for cleaning up the (buffered) connection
            if (response instanceof Response)
            {
               ((Response) response).close();
            }
         }
      }

      @Override
      public void failed(Exception ex)
      {
         invocationCallback.failed(clientException(ex, null));
      }
   }

   
ClientResponse with surefire releaseConnection
/**
    * ClientResponse with surefire releaseConnection
    */
   private static class ConnectionResponse extends FinalizedClientResponse
   {

      private InputStream connection;
      private InputStream stream;

      ConnectionResponse(final ClientConfiguration configuration, final Map<String, Object> properties)
      {
         super(configuration, RESTEasyTracingLogger.empty());
         setProperties(properties);
      }

      public synchronized void setConnection(InputStream connection)
      {
         this.connection = connection;
         this.stream = connection;
      }

      @Override
      protected synchronized void setInputStream(InputStream is)
      {
         stream = is;
         resetEntity();
      }

      @Override
      public synchronized InputStream getInputStream()
      {
         return stream;
      }

      @Override
      public synchronized void releaseConnection() throws IOException
      {
         releaseConnection(false);
      }

      @Override
      public synchronized void releaseConnection(boolean consumeInputStream) throws IOException
      {
         boolean thrown = true;
         try
         {
            if (stream != null)
            {
               if (consumeInputStream)
               {
                  while (stream.read() > 0)
                  {
                  }
               }
               stream.close();
            }
            thrown = false;
         }
         finally
         {
            if (connection != null)
            {
               if (thrown)
               {
                  IOUtils.closeQuietly(connection);
               }
               else
               {
                  connection.close();
               }
            }
         }
      }

   }

   private static class EndOfStream implements ContentDecoder
   {
      public static EndOfStream INSTANCE = new EndOfStream();

      @Override
      public int read(ByteBuffer dst) throws IOException
      {
         return -1;
      }

      @Override
      public boolean isCompleted()
      {
         return true;
      }
   }

   private static HttpUriRequest buildHttpRequest(ClientInvocation request)
   {
      // Writers may change headers. Thus buffer the content before committing the headers.
      // For simplicity's sake the content is buffered in memory. File-buffering (ZeroCopyConsumer...) would be
      // possible, but resource management is error-prone.

      HttpRequestBase httpRequest = createHttpMethod(request.getUri(), request.getMethod());
      if (request.getEntity() != null)
      {
         byte[] requestContent = requestContent(request);
         ByteArrayEntity entity = new ByteArrayEntity(requestContent);
         final MediaType mediaType = request.getHeaders().getMediaType();
         if (mediaType != null) {
            entity.setContentType(new BasicHeader(HTTP.CONTENT_TYPE, mediaType.toString()));
         }
         commitHeaders(request, httpRequest);
         ((HttpEntityEnclosingRequest) httpRequest).setEntity(entity);
      }
      else
      {
         commitHeaders(request, httpRequest);
      }

      return httpRequest;
   }

   private static byte[] requestContent(ClientInvocation request)
   {
      ByteArrayOutputStream baos = new ByteArrayOutputStream();
      request.getDelegatingOutputStream().setDelegate(baos);
      try
      {
         request.writeRequestBody(request.getEntityStream());
         baos.close();
         return baos.toByteArray();
      }
      catch (IOException e)
      {
         throw new RuntimeException(e);
      }
   }

   private static HttpRequestBase createHttpMethod(URI url, String restVerb)
   {
      if ("GET".equals(restVerb))
      {
         return new HttpGet(url);
      }
      else if ("POST".equals(restVerb))
      {
         return new HttpPost(url);
      }
      else
      {
         final String verb = restVerb;
         return new HttpPost(url)
         {
            @Override
            public String getMethod()
            {
               return verb;
            }
         };
      }
   }

   private static void commitHeaders(ClientInvocation request, HttpRequestBase httpMethod)
   {
      MultivaluedMap<String, String> headers = request.getHeaders().asMap();
      for (Map.Entry<String, List<String>> header : headers.entrySet())
      {
         List<String> values = header.getValue();
         for (String value : values)
         {
            httpMethod.addHeader(header.getKey(), value);
         }
      }
   }

   private static void copyResponse(HttpResponse httpResponse, ClientResponse clientResponse)
   {
      clientResponse.setStatus(httpResponse.getStatusLine().getStatusCode());
      CaseInsensitiveMap<String> headers = new CaseInsensitiveMap<String>();
      for (Header header : httpResponse.getAllHeaders())
      {
         headers.add(header.getName(), header.getValue());
      }
      clientResponse.setHeaders(headers);
   }

   private static RuntimeException clientException(Throwable ex, Response clientResponse) {
      RuntimeException ret;
      if (ex == null)
      {
         ret = new ProcessingException(new NullPointerException());
      }
      else if (ex instanceof WebApplicationException)
      {
         ret = (WebApplicationException) ex;
      }
      else if (ex instanceof ProcessingException)
      {
         ret = (ProcessingException) ex;
      }
      else if (clientResponse != null)
      {
         ret = new ResponseProcessingException(clientResponse, ex);
      }
      else
      {
         ret = new ProcessingException(ex);
      }
      return ret;
   }

   private static IOException ioException(Exception ex) {
      return (ex instanceof IOException) ? (IOException) ex : new IOException(ex);
   }

}