netty - AbstractBootstrap#handler vs. ServerBootstrap#childHandler for ServerBootstrap？

Question

我要复活this一和Manish Maheshwari的回答，尤其是。哪里有文件证明

The handler, which is defined in the AbstractBootstrap is used when writing Netty based clients.

和

When writing Netty based servers [use] childHandler as defined in the ServerBootstrap.

换句话说，差异在哪里

val b = new ServerBootstrap()
b.group(boss, wrkr)
 .channel(classOf[NioServerSocketChannel])
 .handler(new LoggingHandler(LogLevel.INFO))
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 .childHandler(new ChannelInitializer[SocketChannel]() {
   override def initChannel(ch: SocketChannel): Unit =
     ch.pipeline()
       .addLast(new LoggingHandler(LogLevel.INFO))
       .addLast(new StringDecoder())
       .addLast(new StringEncoder())
 })

和

val b = new ServerBootstrap()
b.group(boss, wrkr)
 .channel(classOf[NioServerSocketChannel])
 .childHandler(new ChannelInitializer[SocketChannel]() {
   override def initChannel(ch: SocketChannel): Unit =
     ch.pipeline()
       .addLast(new LoggingHandler(LogLevel.INFO))
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
       .addLast(new StringDecoder())
       .addLast(new StringEncoder())
 })

Answer 1

handler为 注册一个 channel 处理程序家长 channel childHandler为 注册一个 channel 处理程序 child channel
看似相同的处理程序在不同的 channel 上监听事件并具有不同的行为。

在 LoggingHandler 的情况下，第一个记录在父 channel 中发生的事件，包括端口绑定(bind)和接受新连接。所以它产生如下日志(简化和注释):

// parent channel registered
INFO - [id: 0xb94a8e7c] REGISTERED
// parent channel binds to localhost:8009
INFO - [id: 0xb94a8e7c] BIND: 0.0.0.0/0.0.0.0:8009
// parent channel active
INFO - [id: 0xb94a8e7c, L:/0:0:0:0:0:0:0:0:8009] ACTIVE
// parent channel accepts new connection, child channel with id 0xe507ce8f created
INFO - [id: 0xb94a8e7c, L:/0:0:0:0:0:0:0:0:8009] RECEIVED: [id: 0xe507ce8f, L:/0:0:0:0:0:0:0:1:8009 - R:/0:0:0:0:0:0:0:1:54398]

假设子 channel 读取请求中的数据，您的第二个记录器将产生如下内容:

// child channel registered
INFO - [id: 0x15fee362, L:/0:0:0:0:0:0:0:1:8009 - R:/0:0:0:0:0:0:0:1:55459] REGISTERED
// child channel active
INFO - [id: 0x15fee362, L:/0:0:0:0:0:0:0:1:8009 - R:/0:0:0:0:0:0:0:1:55459] ACTIVE
// child channel received 7 bytes of data, "hello\r\n"
INFO - [id: 0x15fee362, L:/0:0:0:0:0:0:0:1:8009 - R:/0:0:0:0:0:0:0:1:55459] RECEIVED: 7B
// logs the hex dump of the received data

+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 65 6c 6c 6f 0d 0a |hello.. |
+--------+-------------------------------------------------+----------------+