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Removed the reference to ChannelPipelineCoverage in the getting started guide. Beginners should simply start from creating a new instance for every new connection, as shown in the guide and all examples which were revised to avoid confusion.

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Shared instances are more advanced topic, which will be addressed in another chapter.
This commit is contained in:
Trustin Lee 2010-02-01 23:56:37 +00:00
parent 901b1f099a
commit 2f7c758fe6
1 changed files with 23 additions and 69 deletions
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92
src/docbook/en-US/module/start.xml
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@ -73,15 +73,14 @@
</para>
<programlisting>package org.jboss.netty.example.discard;
@&ChannelPipelineCoverage;("all")<co id="example.discard.co1"/>
public class DiscardServerHandler extends &SimpleChannelHandler; {<co id="example.discard.co2"/>
public class DiscardServerHandler extends &SimpleChannelHandler; {<co id="example.discard.co1"/>
@Override
public void messageReceived(&ChannelHandlerContext; ctx, &MessageEvent; e) {<co id="example.discard.co3"/>
public void messageReceived(&ChannelHandlerContext; ctx, &MessageEvent; e) {<co id="example.discard.co2"/>
}
@Override
public void exceptionCaught(&ChannelHandlerContext; ctx, &ExceptionEvent; e) {<co id="example.discard.co4"/>
public void exceptionCaught(&ChannelHandlerContext; ctx, &ExceptionEvent; e) {<co id="example.discard.co3"/>
e.getCause().printStackTrace();
&Channel; ch = e.getChannel();
@ -90,16 +89,6 @@ public class DiscardServerHandler extends &SimpleChannelHandler; {<co id="exampl
}</programlisting>
<calloutlist>
<callout arearefs="example.discard.co1">
<para>
&ChannelPipelineCoverage; annotates a handler type to tell if the
handler instance of the annotated type can be shared by more than
one &Channel; (and its associated &ChannelPipeline;).
<classname>DiscardServerHandler</classname> does not manage any
stateful information, and therefore it is annotated with the value
<literal>"all"</literal>.
</para>
</callout>
<callout arearefs="example.discard.co2">
<para>
<classname>DiscardServerHandler</classname> extends
&SimpleChannelHandler;, which is an implementation of
@ -109,7 +98,7 @@ public class DiscardServerHandler extends &SimpleChannelHandler; {<co id="exampl
the handler interfaces by yourself.
</para>
</callout>
<callout arearefs="example.discard.co3">
<callout arearefs="example.discard.co2">
<para>
We override the <methodname>messageReceived</methodname> event
handler method here. This method is called with a &MessageEvent;,
@ -118,7 +107,7 @@ public class DiscardServerHandler extends &SimpleChannelHandler; {<co id="exampl
nothing to implement the DISCARD protocol.
</para>
</callout>
<callout arearefs="example.discard.co4">
<callout arearefs="example.discard.co3">
<para>
<methodname>exceptionCaught</methodname> event handler method is
called with an &ExceptionEvent; when an exception was raised by
@ -154,14 +143,14 @@ public class DiscardServer {
bootstrap.setPipelineFactory(new &ChannelPipelineFactory;() {<co id="example.discard2.co3" />
public &ChannelPipeline; getPipeline() {
return &Channels;.pipeline(new DiscardServerHandler());<co id="example.discard2.co4" />
return &Channels;.pipeline(new DiscardServerHandler());
}
});
bootstrap.setOption("child.tcpNoDelay", true);<co id="example.discard2.co5" />
bootstrap.setOption("child.tcpNoDelay", true);<co id="example.discard2.co4" />
bootstrap.setOption("child.keepAlive", true);
bootstrap.bind(new InetSocketAddress(8080));<co id="example.discard2.co6" />
bootstrap.bind(new InetSocketAddress(8080));<co id="example.discard2.co5" />
}
}</programlisting>
<calloutlist>
@ -200,13 +189,6 @@ public class DiscardServer {
</para>
</callout>
<callout arearefs="example.discard2.co4">
<para>
Strictly speaking, we do not need to create a new
<classname>DiscardServerHandler</classname> instance for a new
connection because the handler is stateless.
</para>
</callout>
<callout arearefs="example.discard2.co5">
<para>
You can also set the parameters which are specific to the &Channel;
implementation. We are writing a TCP/IP server, so we are allowed
@ -219,7 +201,7 @@ public class DiscardServer {
<programlisting>bootstrap.setOption("reuseAddress", true);</programlisting>
</para>
</callout>
<callout arearefs="example.discard2.co6">
<callout arearefs="example.discard2.co5">
<para>
We are ready to go now. What's left is to bind to the port and to
start the server. Here, we bind to the port <literal>8080</literal>
@ -260,6 +242,7 @@ public void messageReceived(&ChannelHandlerContext; ctx, &MessageEvent; e) {
&ChannelBuffer;<co id="example.discard3.co1"/> buf = (ChannelBuffer) e.getMessage();
while(buf.readable()) {
System.out.println((char) buf.readByte());
System.out.flush();
}
}</programlisting>
<calloutlist>
@ -353,7 +336,6 @@ public void messageReceived(&ChannelHandlerContext; ctx, &MessageEvent; e) {
</para>
<programlisting>package org.jboss.netty.example.time;
@&ChannelPipelineCoverage;("all")
public class TimeServerHandler extends &SimpleChannelHandler; {
@Override
@ -447,7 +429,7 @@ ch.close();</programlisting>
method after the &ChannelFuture;, which was returned by the
<methodname>write</methodname> method, notifies you when the write
operation has been done. Please note that, <methodname>close</methodname>
might not close the connection immediately, and it returns a
also might not close the connection immediately, and it returns a
&ChannelFuture;.
</para>
</callout>
@ -545,7 +527,6 @@ public class TimeClient {
import java.util.Date;
@&ChannelPipelineCoverage;("all")
public class TimeClientHandler extends &SimpleChannelHandler; {
@Override
@ -633,17 +614,16 @@ import static org.jboss.netty.buffer.&ChannelBuffers;.*;
import java.util.Date;
@&ChannelPipelineCoverage;("one")<co id="example.time3.co1"/>
public class TimeClientHandler extends &SimpleChannelHandler; {
private final &ChannelBuffer; buf = dynamicBuffer();<co id="example.time3.co2"/>
private final &ChannelBuffer; buf = dynamicBuffer();<co id="example.time3.co1"/>
@Override
public void messageReceived(&ChannelHandlerContext; ctx, &MessageEvent; e) {
&ChannelBuffer; m = (&ChannelBuffer;) e.getMessage();
buf.writeBytes(m);<co id="example.time3.co3"/>
buf.writeBytes(m);<co id="example.time3.co2"/>
if (buf.readableBytes() &gt;= 4) {<co id="example.time3.co4"/>
if (buf.readableBytes() &gt;= 4) {<co id="example.time3.co3"/>
long currentTimeMillis = buf.readInt() * 1000L;
System.out.println(new Date(currentTimeMillis));
e.getChannel().close();
@ -658,30 +638,19 @@ public class TimeClientHandler extends &SimpleChannelHandler; {
}</programlisting>
<calloutlist>
<callout arearefs="example.time3.co1">
<para>
This time, <literal>"one"</literal> was used as the value of the
&ChannelPipelineCoverage; annotation. It's because the new
<classname>TimeClientHandler</classname> has to maintain the internal
buffer and therefore cannot serve multiple &Channel;s. If an
instance of <classname>TimeClientHandler</classname> is shared by
multiple &Channel;s (and consequently multiple &ChannelPipeline;s),
the content of the <varname>buf</varname> will be corrupted.
</para>
</callout>
<callout arearefs="example.time3.co2">
<para>
A <firstterm>dynamic buffer</firstterm> is a &ChannelBuffer; which
increases its capacity on demand. It's very useful when you don't
know the length of the message.
</para>
</callout>
<callout arearefs="example.time3.co3">
<callout arearefs="example.time3.co2">
<para>
First, all received data should be cumulated into
<varname>buf</varname>.
</para>
</callout>
<callout arearefs="example.time3.co4">
<callout arearefs="example.time3.co3">
<para>
And then, the handler must check if <varname>buf</varname> has enough
data, 4 bytes in this example, and proceed to the actual business
@ -729,35 +698,28 @@ public class TimeClientHandler extends &SimpleChannelHandler; {
</para>
<programlisting>package org.jboss.netty.example.time;
<co id="example.time4.co1"/>
public class TimeDecoder extends &FrameDecoder; {
@Override
protected Object decode(
&ChannelHandlerContext; ctx, &Channel; channel, &ChannelBuffer; buffer)<co id="example.time4.co2"/> {
&ChannelHandlerContext; ctx, &Channel; channel, &ChannelBuffer; buffer)<co id="example.time4.co1"/> {
if (buffer.readableBytes() &lt; 4) {
return null; <co id="example.time4.co3"/>
return null; <co id="example.time4.co2"/>
}
return buffer.readBytes(4);<co id="example.time4.co4"/>
return buffer.readBytes(4);<co id="example.time4.co3"/>
}
}</programlisting>
<calloutlist>
<callout arearefs="example.time4.co1">
<para>
There's no &ChannelPipelineCoverage; annotation this time because
&FrameDecoder; is already annotated with <literal>"one"</literal>.
</para>
</callout>
<callout arearefs="example.time4.co2">
<para>
&FrameDecoder; calls <methodname>decode</methodname> method with
an internally maintained cumulative buffer whenever new data is
received.
</para>
</callout>
<callout arearefs="example.time4.co3">
<callout arearefs="example.time4.co2">
<para>
If <literal>null</literal> is returned, it means there's not
enough data yet. &FrameDecoder; will call again when there is a
@ -926,27 +888,19 @@ public void channelConnected(&ChannelHandlerContext; ctx, &ChannelStateEvent; e)
import static org.jboss.netty.buffer.&ChannelBuffers;.*;
@&ChannelPipelineCoverage;("all")<co id="example.time6.co1"/>
public class TimeEncoder extends &SimpleChannelHandler; {
public void writeRequested(&ChannelHandlerContext; ctx, &MessageEvent;<co id="example.time6.co2"/> e) {
public void writeRequested(&ChannelHandlerContext; ctx, &MessageEvent;<co id="example.time6.co1"/> e) {
UnixTime time = (UnixTime) e.getMessage();
&ChannelBuffer; buf = buffer(4);
buf.writeInt(time.getValue());
&Channels;.write(ctx, e.getFuture(), buf);<co id="example.time6.co3"/>
&Channels;.write(ctx, e.getFuture(), buf);<co id="example.time6.co2"/>
}
}</programlisting>
<calloutlist>
<callout arearefs="example.time6.co1">
<para>
The &ChannelPipelineCoverage; value of an encoder is usually
<literal>"all"</literal> because this encoder is stateless.
Actually, most encoders are stateless.
</para>
</callout>
<callout arearefs="example.time6.co2">
<para>
An encoder overrides the <methodname>writeRequested</methodname>
method to intercept a write request. Please note that the
@ -962,7 +916,7 @@ public class TimeEncoder extends &SimpleChannelHandler; {
between a upstream event and a downstream event.
</para>
</callout>
<callout arearefs="example.time6.co3">
<callout arearefs="example.time6.co2">
<para>
Once done with transforming a POJO into a &ChannelBuffer;, you should
forward the new buffer to the previous &ChannelDownstreamHandler; in