Java tutorial
/* * Copyright 2011 - 2015 Metamarkets Group Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.metamx.http.client.response; import com.google.common.base.Throwables; import com.google.common.io.ByteSource; import com.metamx.common.logger.Logger; import org.jboss.netty.buffer.ChannelBuffer; import org.jboss.netty.buffer.ChannelBufferInputStream; import org.jboss.netty.handler.codec.http.HttpChunk; import org.jboss.netty.handler.codec.http.HttpResponse; import java.io.IOException; import java.io.InputStream; import java.io.SequenceInputStream; import java.util.Enumeration; import java.util.concurrent.BlockingQueue; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.atomic.AtomicBoolean; import java.util.concurrent.atomic.AtomicLong; /** * A HTTP response handler which uses sequence input streams to create a final InputStream. * Any particular instance is encouraged to overwrite a method and call the super if they need extra handling of the * method parameters. * * This implementation uses a blocking queue to feed a SequenceInputStream that is terminated whenever the handler's Done * method is called or a throwable is detected. * * The resulting InputStream will attempt to terminate normally, but on exception in HttpResponseHandler * may end with an IOException upon read() */ public class SequenceInputStreamResponseHandler implements HttpResponseHandler<InputStream, InputStream> { private static final Logger log = new Logger(SequenceInputStreamResponseHandler.class); private final AtomicLong byteCount = new AtomicLong(0); private final BlockingQueue<InputStream> queue = new LinkedBlockingQueue<>(); private final AtomicBoolean done = new AtomicBoolean(false); @Override public ClientResponse<InputStream> handleResponse(HttpResponse response) { try { queue.put(new ChannelBufferInputStream(response.getContent())); } catch (InterruptedException e) { log.error(e, "Queue appending interrupted"); Thread.currentThread().interrupt(); throw Throwables.propagate(e); } byteCount.addAndGet(response.getContent().readableBytes()); return ClientResponse.<InputStream>finished(new SequenceInputStream(new Enumeration<InputStream>() { @Override public boolean hasMoreElements() { // Done is always true until the last stream has be put in the queue. // Then the stream should be spouting good InputStreams. synchronized (done) { return !done.get() || !queue.isEmpty(); } } @Override public InputStream nextElement() { try { return queue.take(); } catch (InterruptedException e) { log.warn(e, "Thread interrupted while taking from queue"); Thread.currentThread().interrupt(); throw Throwables.propagate(e); } } })); } @Override public ClientResponse<InputStream> handleChunk(ClientResponse<InputStream> clientResponse, HttpChunk chunk) { final ChannelBuffer channelBuffer = chunk.getContent(); final int bytes = channelBuffer.readableBytes(); if (bytes > 0) { try { queue.put(new ChannelBufferInputStream(channelBuffer)); // Queue.size() can be expensive in some implementations, but LinkedBlockingQueue.size is just an AtomicLong log.debug("Added stream. Queue length %d", queue.size()); } catch (InterruptedException e) { log.warn(e, "Thread interrupted while adding to queue"); Thread.currentThread().interrupt(); throw Throwables.propagate(e); } byteCount.addAndGet(bytes); } else { log.debug("Skipping zero length chunk"); } return clientResponse; } @Override public ClientResponse<InputStream> done(ClientResponse<InputStream> clientResponse) { synchronized (done) { try { // An empty byte array is put at the end to give the SequenceInputStream.close() as something to close out // after done is set to true, regardless of the rest of the stream's state. queue.put(ByteSource.empty().openStream()); log.debug("Added terminal empty stream"); } catch (InterruptedException e) { log.warn(e, "Thread interrupted while adding to queue"); Thread.currentThread().interrupt(); throw Throwables.propagate(e); } catch (IOException e) { // This should never happen log.wtf(e, "The empty stream threw an IOException"); throw Throwables.propagate(e); } finally { log.debug("Done after adding %d bytes of streams", byteCount.get()); done.set(true); } } return ClientResponse.<InputStream>finished(clientResponse.getObj()); } @Override public void exceptionCaught(final ClientResponse<InputStream> clientResponse, final Throwable e) { // Don't wait for lock in case the lock had something to do with the error synchronized (done) { done.set(true); // Make a best effort to put a zero length buffer into the queue in case something is waiting on the take() // If nothing is waiting on take(), this will be closed out anyways. final boolean accepted = queue.offer(new InputStream() { @Override public int read() throws IOException { throw new IOException(e); } }); if (!accepted) { log.warn("Unable to place final IOException offer in queue"); } else { log.debug("Placed IOException in queue"); } log.debug(e, "Exception with queue length of %d and %d bytes available", queue.size(), byteCount.get()); } } public final long getByteCount() { return byteCount.get(); } }