http://netty.io/netty-all/: Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers and clients. (The Netty Project) 
public abstract class io.netty.channel.ChannelInitializer<C extends io.netty.channel.Channel> extends io.netty.channel.ChannelInboundHandlerAdapter
  minor version: 0
  major version: 59
  flags: flags: (0x0421) ACC_PUBLIC, ACC_SUPER, ACC_ABSTRACT
  this_class: io.netty.channel.ChannelInitializer
  super_class: io.netty.channel.ChannelInboundHandlerAdapter
{
  private static final io.netty.util.internal.logging.InternalLogger logger;
    descriptor: Lio/netty/util/internal/logging/InternalLogger;
    flags: (0x001a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL

  private final java.util.concurrent.ConcurrentMap<io.netty.channel.ChannelHandlerContext, java.lang.Boolean> initMap;
    descriptor: Ljava/util/concurrent/ConcurrentMap;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL
    Signature: Ljava/util/concurrent/ConcurrentMap<Lio/netty/channel/ChannelHandlerContext;Ljava/lang/Boolean;>;

  static void <clinit>();
    descriptor: ()V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=1, locals=0, args_size=0
         0: .line 55
            ldc Lio/netty/channel/ChannelInitializer;
            invokestatic io.netty.util.internal.logging.InternalLoggerFactory.getInstance:(Ljava/lang/Class;)Lio/netty/util/internal/logging/InternalLogger;
            putstatic io.netty.channel.ChannelInitializer.logger:Lio/netty/util/internal/logging/InternalLogger;
            return
      LocalVariableTable:
        Start  End  Slot  Name  Signature

  public void <init>();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // io.netty.channel.ChannelInitializer this
         0: .line 53
            aload 0 /* this */
            invokespecial io.netty.channel.ChannelInboundHandlerAdapter.<init>:()V
         1: .line 58
            aload 0 /* this */
            invokestatic io.netty.util.internal.PlatformDependent.newConcurrentHashMap:()Ljava/util/concurrent/ConcurrentMap;
            putfield io.netty.channel.ChannelInitializer.initMap:Ljava/util/concurrent/ConcurrentMap;
         2: .line 53
            return
        end local 0 // io.netty.channel.ChannelInitializer this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    3     0  this  Lio/netty/channel/ChannelInitializer<TC;>;

  protected abstract void initChannel();
    descriptor: (Lio/netty/channel/Channel;)V
    flags: (0x0404) ACC_PROTECTED, ACC_ABSTRACT
    Exceptions:
      throws java.lang.Exception
    Signature: (TC;)V
    MethodParameters:
      Name  Flags
      ch    

  public final void channelRegistered(io.netty.channel.ChannelHandlerContext);
    descriptor: (Lio/netty/channel/ChannelHandlerContext;)V
    flags: (0x0011) ACC_PUBLIC, ACC_FINAL
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // io.netty.channel.ChannelInitializer this
        start local 1 // io.netty.channel.ChannelHandlerContext ctx
         0: .line 76
            aload 0 /* this */
            aload 1 /* ctx */
            invokevirtual io.netty.channel.ChannelInitializer.initChannel:(Lio/netty/channel/ChannelHandlerContext;)Z
            ifeq 3
         1: .line 79
            aload 1 /* ctx */
            invokeinterface io.netty.channel.ChannelHandlerContext.pipeline:()Lio/netty/channel/ChannelPipeline;
            invokeinterface io.netty.channel.ChannelPipeline.fireChannelRegistered:()Lio/netty/channel/ChannelPipeline;
            pop
         2: .line 80
            goto 4
         3: .line 82
      StackMap locals:
      StackMap stack:
            aload 1 /* ctx */
            invokeinterface io.netty.channel.ChannelHandlerContext.fireChannelRegistered:()Lio/netty/channel/ChannelHandlerContext;
            pop
         4: .line 84
      StackMap locals:
      StackMap stack:
            return
        end local 1 // io.netty.channel.ChannelHandlerContext ctx
        end local 0 // io.netty.channel.ChannelInitializer this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    5     0  this  Lio/netty/channel/ChannelInitializer<TC;>;
            0    5     1   ctx  Lio/netty/channel/ChannelHandlerContext;
    Exceptions:
      throws java.lang.Exception
    MethodParameters:
      Name  Flags
      ctx   

  public void exceptionCaught(io.netty.channel.ChannelHandlerContext, java.lang.Throwable);
    descriptor: (Lio/netty/channel/ChannelHandlerContext;Ljava/lang/Throwable;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=4, locals=3, args_size=3
        start local 0 // io.netty.channel.ChannelInitializer this
        start local 1 // io.netty.channel.ChannelHandlerContext ctx
        start local 2 // java.lang.Throwable cause
         0: .line 91
            getstatic io.netty.channel.ChannelInitializer.logger:Lio/netty/util/internal/logging/InternalLogger;
            new java.lang.StringBuilder
            dup
            ldc "Failed to initialize a channel. Closing: "
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            aload 1 /* ctx */
            invokeinterface io.netty.channel.ChannelHandlerContext.channel:()Lio/netty/channel/Channel;
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            aload 2 /* cause */
            invokeinterface io.netty.util.internal.logging.InternalLogger.warn:(Ljava/lang/String;Ljava/lang/Throwable;)V
         1: .line 92
            aload 1 /* ctx */
            invokeinterface io.netty.channel.ChannelHandlerContext.close:()Lio/netty/channel/ChannelFuture;
            pop
         2: .line 93
            return
        end local 2 // java.lang.Throwable cause
        end local 1 // io.netty.channel.ChannelHandlerContext ctx
        end local 0 // io.netty.channel.ChannelInitializer this
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0    3     0   this  Lio/netty/channel/ChannelInitializer<TC;>;
            0    3     1    ctx  Lio/netty/channel/ChannelHandlerContext;
            0    3     2  cause  Ljava/lang/Throwable;
    Exceptions:
      throws java.lang.Exception
    MethodParameters:
       Name  Flags
      ctx    
      cause  

  public void handlerAdded(io.netty.channel.ChannelHandlerContext);
    descriptor: (Lio/netty/channel/ChannelHandlerContext;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // io.netty.channel.ChannelInitializer this
        start local 1 // io.netty.channel.ChannelHandlerContext ctx
         0: .line 100
            aload 1 /* ctx */
            invokeinterface io.netty.channel.ChannelHandlerContext.channel:()Lio/netty/channel/Channel;
            invokeinterface io.netty.channel.Channel.isRegistered:()Z
            ifeq 2
         1: .line 105
            aload 0 /* this */
            aload 1 /* ctx */
            invokevirtual io.netty.channel.ChannelInitializer.initChannel:(Lio/netty/channel/ChannelHandlerContext;)Z
            pop
         2: .line 107
      StackMap locals:
      StackMap stack:
            return
        end local 1 // io.netty.channel.ChannelHandlerContext ctx
        end local 0 // io.netty.channel.ChannelInitializer this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    3     0  this  Lio/netty/channel/ChannelInitializer<TC;>;
            0    3     1   ctx  Lio/netty/channel/ChannelHandlerContext;
    Exceptions:
      throws java.lang.Exception
    MethodParameters:
      Name  Flags
      ctx   

  private boolean initChannel(io.netty.channel.ChannelHandlerContext);
    descriptor: (Lio/netty/channel/ChannelHandlerContext;)Z
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=3, locals=4, args_size=2
        start local 0 // io.netty.channel.ChannelInitializer this
        start local 1 // io.netty.channel.ChannelHandlerContext ctx
         0: .line 111
            aload 0 /* this */
            getfield io.netty.channel.ChannelInitializer.initMap:Ljava/util/concurrent/ConcurrentMap;
            aload 1 /* ctx */
            getstatic java.lang.Boolean.TRUE:Ljava/lang/Boolean;
            invokeinterface java.util.concurrent.ConcurrentMap.putIfAbsent:(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
            ifnonnull 11
         1: .line 113
            aload 0 /* this */
            aload 1 /* ctx */
            invokeinterface io.netty.channel.ChannelHandlerContext.channel:()Lio/netty/channel/Channel;
            invokevirtual io.netty.channel.ChannelInitializer.initChannel:(Lio/netty/channel/Channel;)V
         2: .line 114
            goto 9
      StackMap locals:
      StackMap stack: java.lang.Throwable
         3: astore 2 /* cause */
        start local 2 // java.lang.Throwable cause
         4: .line 117
            aload 0 /* this */
            aload 1 /* ctx */
            aload 2 /* cause */
            invokevirtual io.netty.channel.ChannelInitializer.exceptionCaught:(Lio/netty/channel/ChannelHandlerContext;Ljava/lang/Throwable;)V
        end local 2 // java.lang.Throwable cause
         5: .line 119
            aload 0 /* this */
            aload 1 /* ctx */
            invokevirtual io.netty.channel.ChannelInitializer.remove:(Lio/netty/channel/ChannelHandlerContext;)V
            goto 10
         6: .line 118
      StackMap locals:
      StackMap stack: java.lang.Throwable
            astore 3
         7: .line 119
            aload 0 /* this */
            aload 1 /* ctx */
            invokevirtual io.netty.channel.ChannelInitializer.remove:(Lio/netty/channel/ChannelHandlerContext;)V
         8: .line 120
            aload 3
            athrow
         9: .line 119
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            aload 1 /* ctx */
            invokevirtual io.netty.channel.ChannelInitializer.remove:(Lio/netty/channel/ChannelHandlerContext;)V
        10: .line 121
      StackMap locals:
      StackMap stack:
            iconst_1
            ireturn
        11: .line 123
      StackMap locals:
      StackMap stack:
            iconst_0
            ireturn
        end local 1 // io.netty.channel.ChannelHandlerContext ctx
        end local 0 // io.netty.channel.ChannelInitializer this
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0   12     0   this  Lio/netty/channel/ChannelInitializer<TC;>;
            0   12     1    ctx  Lio/netty/channel/ChannelHandlerContext;
            4    5     2  cause  Ljava/lang/Throwable;
      Exception table:
        from    to  target  type
           1     2       3  Class java.lang.Throwable
           1     5       6  any
    Exceptions:
      throws java.lang.Exception
    MethodParameters:
      Name  Flags
      ctx   

  private void remove(io.netty.channel.ChannelHandlerContext);
    descriptor: (Lio/netty/channel/ChannelHandlerContext;)V
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=2, locals=4, args_size=2
        start local 0 // io.netty.channel.ChannelInitializer this
        start local 1 // io.netty.channel.ChannelHandlerContext ctx
         0: .line 128
            aload 1 /* ctx */
            invokeinterface io.netty.channel.ChannelHandlerContext.pipeline:()Lio/netty/channel/ChannelPipeline;
            astore 2 /* pipeline */
        start local 2 // io.netty.channel.ChannelPipeline pipeline
         1: .line 129
            aload 2 /* pipeline */
            aload 0 /* this */
            invokeinterface io.netty.channel.ChannelPipeline.context:(Lio/netty/channel/ChannelHandler;)Lio/netty/channel/ChannelHandlerContext;
            ifnull 7
         2: .line 130
            aload 2 /* pipeline */
            aload 0 /* this */
            invokeinterface io.netty.channel.ChannelPipeline.remove:(Lio/netty/channel/ChannelHandler;)Lio/netty/channel/ChannelPipeline;
            pop
        end local 2 // io.netty.channel.ChannelPipeline pipeline
         3: .line 132
            goto 7
      StackMap locals:
      StackMap stack: java.lang.Throwable
         4: astore 3
         5: .line 133
            aload 0 /* this */
            getfield io.netty.channel.ChannelInitializer.initMap:Ljava/util/concurrent/ConcurrentMap;
            aload 1 /* ctx */
            invokeinterface java.util.concurrent.ConcurrentMap.remove:(Ljava/lang/Object;)Ljava/lang/Object;
            pop
         6: .line 134
            aload 3
            athrow
         7: .line 133
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            getfield io.netty.channel.ChannelInitializer.initMap:Ljava/util/concurrent/ConcurrentMap;
            aload 1 /* ctx */
            invokeinterface java.util.concurrent.ConcurrentMap.remove:(Ljava/lang/Object;)Ljava/lang/Object;
            pop
         8: .line 135
            return
        end local 1 // io.netty.channel.ChannelHandlerContext ctx
        end local 0 // io.netty.channel.ChannelInitializer this
      LocalVariableTable:
        Start  End  Slot      Name  Signature
            0    9     0      this  Lio/netty/channel/ChannelInitializer<TC;>;
            0    9     1       ctx  Lio/netty/channel/ChannelHandlerContext;
            1    3     2  pipeline  Lio/netty/channel/ChannelPipeline;
      Exception table:
        from    to  target  type
           0     4       4  any
    MethodParameters:
      Name  Flags
      ctx   
}
Signature: <C::Lio/netty/channel/Channel;>Lio/netty/channel/ChannelInboundHandlerAdapter;
SourceFile: "ChannelInitializer.java"
InnerClasses:
  public abstract Sharable = io.netty.channel.ChannelHandler$Sharable of io.netty.channel.ChannelHandler
    RuntimeVisibleAnnotations: 
      io.netty.channel.ChannelHandler$Sharable()