java - 扩展 ChannelHandlerAdapter，但不重写或实现 ChannelHandlerAdapter 中的方法

Question

这个方法来自 EchoClientHandler 是什么意思？覆盖？

@Override
public void channelActive(ChannelHandlerContext ctx) {
    ctx.writeAndFlush(firstMessage);
}

编译错误:

-do-compile:
    [mkdir] Created dir: /home/thufir/NetBeansProjects/NettyEcho/build/empty
    [mkdir] Created dir: /home/thufir/NetBeansProjects/NettyEcho/build/generated-sources/ap-source-output
    [javac] Compiling 4 source files to /home/thufir/NetBeansProjects/NettyEcho/build/classes
    [javac] /home/thufir/NetBeansProjects/NettyEcho/src/io/netty/example/echo/EchoClientHandler.java:27: error: method does not override or implement a method from a supertype
    [javac]     @Override
    [javac]     ^

来自github的代码:

package io.netty.example.echo;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

/**
* Handler implementation for the echo client. It initiates the ping-pong
* traffic between the echo client and server by sending the first message to
* the server.
*/
public class EchoClientHandler extends ChannelHandlerAdapter {

    private final ByteBuf firstMessage;

    /**
* Creates a client-side handler.
*/
    public EchoClientHandler() {
        firstMessage = Unpooled.buffer(EchoClient.SIZE);
        for (int i = 0; i < firstMessage.capacity(); i ++) {
            firstMessage.writeByte((byte) i);
        }
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ctx.writeAndFlush(firstMessage);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        ctx.write(msg);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
       ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // Close the connection when an exception is raised.
        cause.printStackTrace();
        ctx.close();
    }
}

当我查看ChannelHandlerAdapter时，我没有看到这些方法...

Answer 1

您混淆了版本。

在 Netty 4 中，您有 EchoClientHandler :

public class  EchoClientHandler extends ChannelInboundHandlerAdapter 

在 Netty 4 中，ChannelInboundHandlerAdapter有一个 channelActive 方法。

您的链接适用于 EchoClientHandler在 Netty 5 中，ChannelHandlerAdapter已更新并具有更多方法，包括 channelActive。