Handle an empty ByteBuf specially in HttpObjectEncoder
Related: #2983 Motivation: It is a well known idiom to write an empty buffer and add a listener to its future to close a channel when the last byte has been written out: ChannelFuture f = channel.writeAndFlush(Unpooled.EMPTY_BUFFER); f.addListener(ChannelFutureListener.CLOSE); When HttpObjectEncoder is in the pipeline, this still works, but it silently raises an IllegalStateException, because HttpObjectEncoder does not allow writing a ByteBuf when it is expecting an HttpMessage. Modifications: - Handle an empty ByteBuf specially in HttpObjectEncoder, so that writing an empty buffer does not fail even if the pipeline contains an HttpObjectEncoder - Add a test Result: An exception is not triggered anymore by HttpObjectEncoder, when a user attempts to write an empty buffer.
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@ -74,7 +74,20 @@ public abstract class HttpObjectEncoder<H extends HttpMessage> extends MessageTo
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buf.writeBytes(CRLF);
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state = HttpHeaderUtil.isTransferEncodingChunked(m) ? ST_CONTENT_CHUNK : ST_CONTENT_NON_CHUNK;
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}
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// Bypass the encoder in case of an empty buffer, so that the following idiom works:
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//
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// ch.write(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
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//
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// See https://github.com/netty/netty/issues/2983 for more information.
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if (msg instanceof ByteBuf && !((ByteBuf) msg).isReadable()) {
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out.add(EMPTY_BUFFER);
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return;
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}
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if (msg instanceof HttpContent || msg instanceof ByteBuf || msg instanceof FileRegion) {
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if (state == ST_INIT) {
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throw new IllegalStateException("unexpected message type: " + StringUtil.simpleClassName(msg));
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}
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@ -16,6 +16,7 @@
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package io.netty.handler.codec.http;
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import io.netty.buffer.ByteBuf;
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import io.netty.buffer.Unpooled;
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import io.netty.channel.FileRegion;
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import io.netty.channel.embedded.EmbeddedChannel;
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import io.netty.util.CharsetUtil;
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@ -24,6 +25,7 @@ import org.junit.Test;
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import java.io.IOException;
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import java.nio.channels.WritableByteChannel;
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import static org.hamcrest.Matchers.*;
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import static org.junit.Assert.*;
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public class HttpResponseEncoderTest {
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@ -119,4 +121,28 @@ public class HttpResponseEncoderTest {
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return false;
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}
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}
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@Test
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public void testEmptyBufferBypass() throws Exception {
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EmbeddedChannel channel = new EmbeddedChannel(new HttpResponseEncoder());
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// Test writing an empty buffer works when the encoder is at ST_INIT.
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channel.writeOutbound(Unpooled.EMPTY_BUFFER);
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ByteBuf buffer = channel.readOutbound();
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assertThat(buffer, is(sameInstance(Unpooled.EMPTY_BUFFER)));
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// Leave the ST_INIT state.
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HttpResponse response = new DefaultHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
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assertTrue(channel.writeOutbound(response));
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buffer = channel.readOutbound();
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assertEquals("HTTP/1.1 200 OK\r\n\r\n", buffer.toString(CharsetUtil.US_ASCII));
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buffer.release();
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// Test writing an empty buffer works when the encoder is not at ST_INIT.
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channel.writeOutbound(Unpooled.EMPTY_BUFFER);
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buffer = channel.readOutbound();
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assertThat(buffer, is(sameInstance(Unpooled.EMPTY_BUFFER)));
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assertFalse(channel.finish());
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}
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}
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