434056 - Support content consumed asynchronously.

Implemented content consumed asynchronously for FastCGI (on the client).

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/client/http/HttpChannelOverFCGI.java

@@ -103,11 +103,13 @@ public class HttpChannelOverFCGI extends HttpChannel
         return exchange != null && receiver.responseHeaders(exchange);
     }
 
-    protected boolean content(ByteBuffer buffer)
+    protected boolean content(ByteBuffer buffer, Callback callback)
     {
         HttpExchange exchange = getHttpExchange();
-        // TODO: handle callback properly
-        return exchange != null && receiver.responseContent(exchange, buffer, new Callback.Adapter());
+        if (exchange != null)
+            return receiver.responseContent(exchange, buffer, callback);
+        callback.succeeded();
+        return false;
     }
 
     protected boolean responseSuccess()

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/client/http/HttpConnectionOverFCGI.java

@@ -45,6 +45,7 @@ import org.eclipse.jetty.io.AbstractConnection;
 import org.eclipse.jetty.io.ByteBufferPool;
 import org.eclipse.jetty.io.EndPoint;
 import org.eclipse.jetty.util.BufferUtil;
+import org.eclipse.jetty.util.CompletableCallback;
 import org.eclipse.jetty.util.log.Log;
 import org.eclipse.jetty.util.log.Logger;
 
@@ -60,6 +61,7 @@ public class HttpConnectionOverFCGI extends AbstractConnection implements Connec
     private final boolean multiplexed;
     private final Delegate delegate;
     private final ClientParser parser;
+    private ByteBuffer buffer;
 
     public HttpConnectionOverFCGI(EndPoint endPoint, HttpDestination destination, boolean multiplexed)
     {
@@ -98,48 +100,66 @@ public class HttpConnectionOverFCGI extends AbstractConnection implements Connec
     @Override
     public void onFillable()
     {
-        EndPoint endPoint = getEndPoint();
         HttpClient client = destination.getHttpClient();
         ByteBufferPool bufferPool = client.getByteBufferPool();
-        ByteBuffer buffer = bufferPool.acquire(client.getResponseBufferSize(), true);
-        try
+        buffer = bufferPool.acquire(client.getResponseBufferSize(), true);
+        process();
+    }
+
+    private void process()
+    {
+        if (readAndParse())
         {
-            while (true)
+            HttpClient client = destination.getHttpClient();
+            ByteBufferPool bufferPool = client.getByteBufferPool();
+            bufferPool.release(buffer);
+            // Don't linger the buffer around if we are idle.
+            buffer = null;
+        }
+    }
+
+    private boolean readAndParse()
+    {
+        EndPoint endPoint = getEndPoint();
+        ByteBuffer buffer = this.buffer;
+        while (true)
+        {
+            try
             {
+                if (!parse(buffer))
+                    return false;
+
                 int read = endPoint.fill(buffer);
                 if (LOG.isDebugEnabled()) // Avoid boxing of variable 'read'.
                     LOG.debug("Read {} bytes from {}", read, endPoint);
                 if (read > 0)
                 {
-                    parse(buffer);
+                    if (!parse(buffer))
+                        return false;
                 }
                 else if (read == 0)
                 {
                     fillInterested();
-                    break;
+                    return true;
                 }
                 else
                 {
                     shutdown();
-                    break;
+                    return true;
                 }
             }
-        }
-        catch (Exception x)
-        {
-            LOG.debug(x);
-            close(x);
-        }
-        finally
-        {
-            bufferPool.release(buffer);
+            catch (Exception x)
+            {
+                LOG.debug(x);
+                close(x);
+                return false;
+            }
         }
     }
 
-    private void parse(ByteBuffer buffer)
+    private boolean parse(ByteBuffer buffer)
     {
-        while (buffer.hasRemaining())
-            parser.parse(buffer);
+        return !parser.parse(buffer);
     }
 
     private void shutdown()
@@ -313,7 +333,7 @@ public class HttpConnectionOverFCGI extends AbstractConnection implements Connec
         }
 
         @Override
-        public void onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
+        public boolean onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
         {
             switch (stream)
             {
@@ -321,7 +341,25 @@ public class HttpConnectionOverFCGI extends AbstractConnection implements Connec
                 {
                     HttpChannelOverFCGI channel = channels.get(request);
                     if (channel != null)
-                        channel.content(buffer);
+                    {
+                        CompletableCallback callback = new CompletableCallback()
+                        {
+                            @Override
+                            public void resume()
+                            {
+                                LOG.debug("Content consumed asynchronously, resuming processing");
+                                process();
+                            }
+
+                            @Override
+                            public void abort(Throwable x)
+                            {
+                                close(x);
+                            }
+                        };
+                        channel.content(buffer, callback);
+                        return callback.tryComplete();
+                    }
                     else
                         noChannel(request);
                     break;
@@ -336,6 +374,7 @@ public class HttpConnectionOverFCGI extends AbstractConnection implements Connec
                     throw new IllegalArgumentException();
                 }
             }
+            return false;
         }
 
         @Override

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/BeginRequestContentParser.java

@@ -37,7 +37,7 @@ public class BeginRequestContentParser extends ContentParser
     }
 
     @Override
-    public boolean parse(ByteBuffer buffer)
+    public Result parse(ByteBuffer buffer)
     {
         while (buffer.hasRemaining())
         {
@@ -78,7 +78,7 @@ public class BeginRequestContentParser extends ContentParser
                         buffer.position(buffer.position() + 5);
                         onStart();
                         reset();
-                        return true;
+                        return Result.COMPLETE;
                     }
                     else
                     {
@@ -94,7 +94,7 @@ public class BeginRequestContentParser extends ContentParser
                     {
                         onStart();
                         reset();
-                        return true;
+                        return Result.COMPLETE;
                     }
                     break;
                 }
@@ -104,7 +104,7 @@ public class BeginRequestContentParser extends ContentParser
                 }
             }
         }
-        return false;
+        return Result.PENDING;
     }
 
     private void onStart()

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/ClientParser.java

@@ -86,9 +86,9 @@ public class ClientParser extends Parser
         }
 
         @Override
-        public void onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
+        public boolean onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
         {
-            listener.onContent(request, stream, buffer);
+            return listener.onContent(request, stream, buffer);
         }
 
         @Override

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/ContentParser.java

@@ -29,7 +29,7 @@ public abstract class ContentParser
         this.headerParser = headerParser;
     }
 
-    public abstract boolean parse(ByteBuffer buffer);
+    public abstract Result parse(ByteBuffer buffer);
 
     public void noContent()
     {
@@ -45,4 +45,9 @@ public abstract class ContentParser
     {
         return headerParser.getContentLength();
     }
+
+    public enum Result
+    {
+        PENDING, ASYNC, COMPLETE
+    }
 }

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/EndRequestContentParser.java

@@ -35,7 +35,7 @@ public class EndRequestContentParser extends ContentParser
     }
 
     @Override
-    public boolean parse(ByteBuffer buffer)
+    public Result parse(ByteBuffer buffer)
     {
         while (buffer.hasRemaining())
         {
@@ -76,7 +76,7 @@ public class EndRequestContentParser extends ContentParser
                         buffer.position(buffer.position() + 3);
                         onEnd();
                         reset();
-                        return true;
+                        return Result.COMPLETE;
                     }
                     else
                     {
@@ -92,7 +92,7 @@ public class EndRequestContentParser extends ContentParser
                     {
                         onEnd();
                         reset();
-                        return true;
+                        return Result.COMPLETE;
                     }
                     break;
                 }
@@ -102,7 +102,7 @@ public class EndRequestContentParser extends ContentParser
                 }
             }
         }
-        return false;
+        return Result.PENDING;
     }
 
     private void onEnd()

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/HeaderParser.java

@@ -32,6 +32,12 @@ public class HeaderParser
     private int length;
     private int padding;
 
+    /**
+     * Parses the bytes in the given {@code buffer} as FastCGI header bytes
+     *
+     * @param buffer the bytes to parse
+     * @return whether there were enough bytes for a FastCGI header
+     */
     public boolean parse(ByteBuffer buffer)
     {
         while (buffer.hasRemaining())

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/ParamsContentParser.java

@@ -45,7 +45,7 @@ public class ParamsContentParser extends ContentParser
     }
 
     @Override
-    public boolean parse(ByteBuffer buffer)
+    public Result parse(ByteBuffer buffer)
     {
         while (buffer.hasRemaining() || state == State.PARAM)
         {
@@ -185,7 +185,7 @@ public class ParamsContentParser extends ContentParser
                     if (length == 0)
                     {
                         reset();
-                        return true;
+                        return Result.COMPLETE;
                     }
                     break;
                 }
@@ -195,7 +195,7 @@ public class ParamsContentParser extends ContentParser
                 }
             }
         }
-        return false;
+        return Result.PENDING;
     }
 
     @Override

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/Parser.java

@@ -29,7 +29,7 @@ public abstract class Parser
     private State state = State.HEADER;
     private int padding;
 
-    public void parse(ByteBuffer buffer)
+    public boolean parse(ByteBuffer buffer)
     {
         while (true)
         {
@@ -38,7 +38,7 @@ public abstract class Parser
                 case HEADER:
                 {
                     if (!headerParser.parse(buffer))
-                        return;
+                        return false;
                     state = State.CONTENT;
                     break;
                 }
@@ -51,8 +51,11 @@ public abstract class Parser
                     }
                     else
                     {
-                        if (!contentParser.parse(buffer))
-                            return;
+                        ContentParser.Result result = contentParser.parse(buffer);
+                        if (result == ContentParser.Result.PENDING)
+                            return false;
+                        else if (result == ContentParser.Result.ASYNC)
+                            return true;
                     }
                     padding = headerParser.getPaddingLength();
                     state = State.PADDING;
@@ -70,7 +73,7 @@ public abstract class Parser
                     {
                         padding -= buffer.remaining();
                         buffer.position(buffer.limit());
-                        return;
+                        return false;
                     }
                 }
                 default:
@@ -96,7 +99,7 @@ public abstract class Parser
 
         public void onHeaders(int request);
 
-        public void onContent(int request, FCGI.StreamType stream, ByteBuffer buffer);
+        public boolean onContent(int request, FCGI.StreamType stream, ByteBuffer buffer);
 
         public void onEnd(int request);
 
@@ -115,8 +118,9 @@ public abstract class Parser
             }
 
             @Override
-            public void onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
+            public boolean onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
             {
+                return false;
             }
 
             @Override

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/ResponseContentParser.java

@@ -52,7 +52,7 @@ public class ResponseContentParser extends StreamContentParser
     }
 
     @Override
-    protected void onContent(ByteBuffer buffer)
+    protected boolean onContent(ByteBuffer buffer)
     {
         int request = getRequest();
         ResponseParser parser = parsers.get(request);
@@ -61,7 +61,7 @@ public class ResponseContentParser extends StreamContentParser
             parser = new ResponseParser(listener, request);
             parsers.put(request, parser);
         }
-        parser.parse(buffer);
+        return parser.parse(buffer);
     }
 
     @Override
@@ -87,7 +87,7 @@ public class ResponseContentParser extends StreamContentParser
             this.httpParser = new FCGIHttpParser(this);
         }
 
-        public void parse(ByteBuffer buffer)
+        public boolean parse(ByteBuffer buffer)
         {
             LOG.debug("Response {} {} content {} {}", request, FCGI.StreamType.STD_OUT, state, buffer);
 
@@ -117,7 +117,8 @@ public class ResponseContentParser extends StreamContentParser
                     }
                     case RAW_CONTENT:
                     {
-                        notifyContent(buffer);
+                        if (notifyContent(buffer))
+                            return true;
                         remaining = 0;
                         break;
                     }
@@ -133,6 +134,7 @@ public class ResponseContentParser extends StreamContentParser
                     }
                 }
             }
+            return false;
         }
 
         @Override
@@ -253,15 +255,16 @@ public class ResponseContentParser extends StreamContentParser
             return false;
         }
 
-        private void notifyContent(ByteBuffer buffer)
+        private boolean notifyContent(ByteBuffer buffer)
         {
             try
             {
-                listener.onContent(request, FCGI.StreamType.STD_OUT, buffer);
+                return listener.onContent(request, FCGI.StreamType.STD_OUT, buffer);
             }
             catch (Throwable x)
             {
                 logger.debug("Exception while invoking listener " + listener, x);
+                return false;
             }
         }
 

jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/StreamContentParser.java

@@ -41,7 +41,7 @@ public class StreamContentParser extends ContentParser
     }
 
     @Override
-    public boolean parse(ByteBuffer buffer)
+    public Result parse(ByteBuffer buffer)
     {
         while (buffer.hasRemaining())
         {
@@ -59,14 +59,15 @@ public class StreamContentParser extends ContentParser
                     int limit = buffer.limit();
                     buffer.limit(buffer.position() + length);
                     ByteBuffer slice = buffer.slice();
-                    onContent(slice);
                     buffer.position(buffer.limit());
                     buffer.limit(limit);
                     contentLength -= length;
+                    if (onContent(slice))
+                        return Result.ASYNC;
                     if (contentLength > 0)
                         break;
                     state = State.LENGTH;
-                    return true;
+                    return Result.COMPLETE;
                 }
                 default:
                 {
@@ -74,7 +75,7 @@ public class StreamContentParser extends ContentParser
                 }
             }
         }
-        return false;
+        return Result.PENDING;
     }
 
     @Override
@@ -90,15 +91,16 @@ public class StreamContentParser extends ContentParser
         }
     }
 
-    protected void onContent(ByteBuffer buffer)
+    protected boolean onContent(ByteBuffer buffer)
     {
         try
         {
-            listener.onContent(getRequest(), streamType, buffer);
+            return listener.onContent(getRequest(), streamType, buffer);
         }
         catch (Throwable x)
         {
             logger.debug("Exception while invoking listener " + listener, x);
+            return false;
         }
     }
 

jetty-fcgi/fcgi-client/src/test/java/org/eclipse/jetty/fcgi/generator/ClientGeneratorTest.java

@@ -158,10 +158,11 @@ public class ClientGeneratorTest
         ServerParser parser = new ServerParser(new ServerParser.Listener.Adapter()
         {
             @Override
-            public void onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
+            public boolean onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
             {
                 Assert.assertEquals(id, request);
                 totalLength.addAndGet(buffer.remaining());
+                return false;
             }
 
             @Override

jetty-fcgi/fcgi-client/src/test/java/org/eclipse/jetty/fcgi/parser/ClientParserTest.java

@@ -117,10 +117,11 @@ public class ClientParserTest
         ClientParser parser = new ClientParser(new ClientParser.Listener.Adapter()
         {
             @Override
-            public void onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
+            public boolean onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
             {
                 Assert.assertEquals(id, request);
                 verifier.addAndGet(2);
+                return false;
             }
 
             @Override
@@ -168,11 +169,12 @@ public class ClientParserTest
         ClientParser parser = new ClientParser(new ClientParser.Listener.Adapter()
         {
             @Override
-            public void onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
+            public boolean onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
             {
                 Assert.assertEquals(id, request);
                 Assert.assertEquals(contentLength, buffer.remaining());
                 verifier.addAndGet(2);
+                return false;
             }
 
             @Override
@@ -221,10 +223,11 @@ public class ClientParserTest
         ClientParser parser = new ClientParser(new ClientParser.Listener.Adapter()
         {
             @Override
-            public void onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
+            public boolean onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
             {
                 Assert.assertEquals(id, request);
                 totalLength.addAndGet(buffer.remaining());
+                return false;
             }
 
             @Override

jetty-fcgi/fcgi-server/src/main/java/org/eclipse/jetty/fcgi/server/ServerFCGIConnection.java

@@ -151,7 +151,7 @@ public class ServerFCGIConnection extends AbstractConnection
         }
 
         @Override
-        public void onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
+        public boolean onContent(int request, FCGI.StreamType stream, ByteBuffer buffer)
         {
             HttpChannelOverFCGI channel = channels.get(request);
             if (LOG.isDebugEnabled())
@@ -161,6 +161,7 @@ public class ServerFCGIConnection extends AbstractConnection
                 if (channel.content(buffer))
                     channel.dispatch();
             }
+            return false;
         }
 
         @Override

jetty-fcgi/fcgi-server/src/main/java/org/eclipse/jetty/fcgi/server/proxy/FastCGIProxyServlet.java

@@ -32,6 +32,7 @@ import org.eclipse.jetty.fcgi.FCGI;
 import org.eclipse.jetty.fcgi.client.http.HttpClientTransportOverFCGI;
 import org.eclipse.jetty.http.HttpFields;
 import org.eclipse.jetty.http.HttpScheme;
+import org.eclipse.jetty.proxy.AsyncProxyServlet;
 import org.eclipse.jetty.proxy.ProxyServlet;
 
 /**
@@ -57,7 +58,7 @@ import org.eclipse.jetty.proxy.ProxyServlet;
  *
  * @see TryFilesFilter
  */
-public class FastCGIProxyServlet extends ProxyServlet.Transparent
+public class FastCGIProxyServlet extends AsyncProxyServlet.Transparent
 {
     public static final String SCRIPT_ROOT_INIT_PARAM = "scriptRoot";
     public static final String SCRIPT_PATTERN_INIT_PARAM = "scriptPattern";

jetty-fcgi/fcgi-server/src/test/java/org/eclipse/jetty/fcgi/server/HttpClientTest.java

@@ -30,6 +30,7 @@ import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.zip.GZIPOutputStream;
 import javax.servlet.ServletException;
 import javax.servlet.ServletOutputStream;
@@ -47,6 +48,7 @@ import org.eclipse.jetty.http.HttpMethod;
 import org.eclipse.jetty.server.handler.AbstractHandler;
 import org.eclipse.jetty.toolchain.test.IO;
 import org.eclipse.jetty.toolchain.test.annotation.Slow;
+import org.eclipse.jetty.util.Callback;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -567,7 +569,7 @@ public class HttpClientTest extends AbstractHttpClientServerTest
                 // Promise some content, then flush the headers, then fail to send the content.
                 response.setContentLength(16);
                 response.flushBuffer();
-                throw new NullPointerException();
+                throw new NullPointerException("Explicitly thrown by test");
             }
         });
 
@@ -627,4 +629,75 @@ public class HttpClientTest extends AbstractHttpClientServerTest
         Assert.assertEquals(200, response.getStatus());
         Assert.assertArrayEquals(data, response.getContent());
     }
+
+    @Test
+    public void testSmallAsyncContent() throws Exception
+    {
+        start(new AbstractHandler()
+        {
+            @Override
+            public void handle(String target, org.eclipse.jetty.server.Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
+            {
+                ServletOutputStream output = response.getOutputStream();
+                output.write(65);
+                output.flush();
+                output.write(66);
+            }
+        });
+
+        final AtomicInteger contentCount = new AtomicInteger();
+        final AtomicReference<Callback> callbackRef = new AtomicReference<>();
+        final AtomicReference<CountDownLatch> contentLatch = new AtomicReference<>(new CountDownLatch(1));
+        final CountDownLatch completeLatch = new CountDownLatch(1);
+        client.newRequest("localhost", connector.getLocalPort())
+                .scheme(scheme)
+                .onResponseContentAsync(new Response.AsyncContentListener()
+                {
+                    @Override
+                    public void onContent(Response response, ByteBuffer content, Callback callback)
+                    {
+                        contentCount.incrementAndGet();
+                        callbackRef.set(callback);
+                        contentLatch.get().countDown();
+                    }
+                })
+                .send(new Response.CompleteListener()
+                {
+                    @Override
+                    public void onComplete(Result result)
+                    {
+                        completeLatch.countDown();
+                    }
+                });
+
+        Assert.assertTrue(contentLatch.get().await(5, TimeUnit.SECONDS));
+        Callback callback = callbackRef.get();
+
+        // Wait a while to be sure that the parsing does not proceed.
+        TimeUnit.MILLISECONDS.sleep(1000);
+
+        Assert.assertEquals(1, contentCount.get());
+
+        // Succeed the content callback to proceed with parsing.
+        callbackRef.set(null);
+        contentLatch.set(new CountDownLatch(1));
+        callback.succeeded();
+
+        Assert.assertTrue(contentLatch.get().await(5, TimeUnit.SECONDS));
+        callback = callbackRef.get();
+
+        // Wait a while to be sure that the parsing does not proceed.
+        TimeUnit.MILLISECONDS.sleep(1000);
+
+        Assert.assertEquals(2, contentCount.get());
+        Assert.assertEquals(1, completeLatch.getCount());
+
+        // Succeed the content callback to proceed with parsing.
+        callbackRef.set(null);
+        contentLatch.set(new CountDownLatch(1));
+        callback.succeeded();
+
+        Assert.assertTrue(completeLatch.await(555, TimeUnit.SECONDS));
+        Assert.assertEquals(2, contentCount.get());
+    }
 }

jetty-proxy/src/main/java/org/eclipse/jetty/proxy/AsyncProxyServlet.java

@@ -19,9 +19,12 @@
 package org.eclipse.jetty.proxy;
 
 import java.io.IOException;
+import java.net.URI;
 import java.nio.ByteBuffer;
 import java.nio.channels.WritePendingException;
 import javax.servlet.ReadListener;
+import javax.servlet.ServletConfig;
+import javax.servlet.ServletException;
 import javax.servlet.ServletInputStream;
 import javax.servlet.ServletOutputStream;
 import javax.servlet.WriteListener;
@@ -79,6 +82,24 @@ public class AsyncProxyServlet extends ProxyServlet
             onResponseFailure(request, response, proxyResponse, x);
         }
     }
+    
+    public static class Transparent extends AsyncProxyServlet
+    {
+        private final TransparentDelegate delegate = new TransparentDelegate(this);
+
+        @Override
+        public void init(ServletConfig config) throws ServletException
+        {
+            super.init(config);
+            delegate.init(config);
+        }
+
+        @Override
+        protected URI rewriteURI(HttpServletRequest request)
+        {
+            return delegate.rewriteURI(request);
+        }
+    }
 
     private class StreamReader implements ReadListener, Callback
     {

jetty-proxy/src/main/java/org/eclipse/jetty/proxy/ProxyServlet.java

@@ -646,26 +646,35 @@ public class ProxyServlet extends HttpServlet
      */
     public static class Transparent extends ProxyServlet
     {
-        private String _proxyTo;
-        private String _prefix;
+        private final TransparentDelegate delegate = new TransparentDelegate(this);
 
-        public Transparent()
+        @Override
+        public void init(ServletConfig config) throws ServletException
         {
-        }
-
-        public Transparent(String proxyTo, String prefix)
-        {
-            _proxyTo = URI.create(proxyTo).normalize().toString();
-            _prefix = URI.create(prefix).normalize().toString();
+            super.init(config);
+            delegate.init(config);
         }
 
         @Override
-        public void init() throws ServletException
+        protected URI rewriteURI(HttpServletRequest request)
         {
-            super.init();
+            return delegate.rewriteURI(request);
+        }
+    }
 
-            ServletConfig config = getServletConfig();
+    protected static class TransparentDelegate
+    {
+        private final ProxyServlet proxyServlet;
+        private String _proxyTo;
+        private String _prefix;
 
+        protected TransparentDelegate(ProxyServlet proxyServlet)
+        {
+            this.proxyServlet = proxyServlet;
+        }
+
+        protected void init(ServletConfig config) throws ServletException
+        {
             String proxyTo = config.getInitParameter("proxyTo");
             _proxyTo = proxyTo == null ? _proxyTo : proxyTo;
 
@@ -681,13 +690,12 @@ public class ProxyServlet extends HttpServlet
             }
 
             // Adjust prefix value to account for context path
-            String contextPath = getServletContext().getContextPath();
+            String contextPath = config.getServletContext().getContextPath();
             _prefix = _prefix == null ? contextPath : (contextPath + _prefix);
 
-            _log.debug(config.getServletName() + " @ " + _prefix + " to " + _proxyTo);
+            proxyServlet._log.debug(config.getServletName() + " @ " + _prefix + " to " + _proxyTo);
         }
 
-        @Override
         protected URI rewriteURI(HttpServletRequest request)
         {
             String path = request.getRequestURI();
@@ -706,7 +714,7 @@ public class ProxyServlet extends HttpServlet
                 uri.append("?").append(query);
             URI rewrittenURI = URI.create(uri.toString()).normalize();
 
-            if (!validateDestination(rewrittenURI.getHost(), rewrittenURI.getPort()))
+            if (!proxyServlet.validateDestination(rewrittenURI.getHost(), rewrittenURI.getPort()))
                 return null;
 
             return rewrittenURI;

jetty-proxy/src/test/java/org/eclipse/jetty/proxy/ProxyServletTest.java

@@ -593,8 +593,11 @@ public class ProxyServletTest
         });
 
         String proxyTo = "http://localhost:" + serverConnector.getLocalPort();
-        proxyServlet = new ProxyServlet.Transparent(proxyTo, prefix);
-        prepareProxy();
+        proxyServlet = new ProxyServlet.Transparent();
+        Map<String, String> params = new HashMap<>();
+        params.put("proxyTo", proxyTo);
+        params.put("prefix", prefix);
+        prepareProxy(params);
 
         // Make the request to the proxy, it should transparently forward to the server
         ContentResponse response = client.newRequest("localhost", proxyConnector.getLocalPort())
@@ -632,8 +635,11 @@ public class ProxyServletTest
 
         String proxyTo = "http://localhost:" + serverConnector.getLocalPort();
         String prefix = "/proxy";
-        proxyServlet = new ProxyServlet.Transparent(proxyTo, prefix);
-        prepareProxy();
+        proxyServlet = new ProxyServlet.Transparent();
+        Map<String, String> params = new HashMap<>();
+        params.put("proxyTo", proxyTo);
+        params.put("prefix", prefix);
+        prepareProxy(params);
 
         // Make the request to the proxy, it should transparently forward to the server
         ContentResponse response = client.newRequest("localhost", proxyConnector.getLocalPort())