title: netty ChannelPipeline addLast
body: <p>I am learning netty and there is a following code from example</p>
  
  <pre><code>ChannelPipeline pipeline = pipeline();
  // Enable stream compression (you can remove these two if unnecessary)
  pipeline.addLast("deflater", new ZlibEncoder(ZlibWrapper.GZIP));
  pipeline.addLast("inflater", new ZlibDecoder(ZlibWrapper.GZIP));
  
  // Add the number codec first,
  pipeline.addLast("decoder", new BigIntegerDecoder());
  pipeline.addLast("encoder", new NumberEncoder());
  
  // and then business logic.
  // Please note we create a handler for every new channel
  // because it has stateful properties.
  pipeline.addLast("handler", new FactorialServerHandler());
  </code></pre>
  
  <p>My question is where can I see the list of valid 1st parameters for addLast method, like deflater, inflater, decoder, encoder, handler and so on. </p>
  
  <p>And I cannot find the place in source code where mapping is implemented. Here I mean message arrive and ChannelPipeline checks that deflater is set and calls ZlibEncoder.GZIP method.</p>