一、需要注意的地方： 入站的消息会流经所有的添加的ChannelInboundHandler,出站的消息不一定会流经所有的ChannelOutboundHandler,通过在某个ChannelInboundHandler的ChannelHandlerContext的writeAndFlush方法写出的数据，并不会流经其后的ChannelOuntboundHandler,但如果是通过ctx.channel().writeAndFlush方法写出数据，则会流经所有的ChannelOutboundHandler.
例如，服务端这样添加Handler,
protected void initChannel(Channel ch) throws Exception {
ch.pipeline().addLast(new MyChannelInboundHandler1());
ch.pipeline().addLast(new MyChannelInboundHandler2());
ch.pipeline().addLast(new MyChannelOutboundHandler1());
}
则形成in1 -> in2 -> out1 的handler处理链，
在in1 和in 2中 进行如下操作，
ctx.writeAndFlush("Welcome to Netty......");
则该数据不会流经out1.要想让数据流经out1,则有两种修改方式：
1.
ctx.channel().writeAndFlush("Welcome to Netty......");
2.修改server中ChannelHandler的添加顺序，把ChannelOutboundHandler1放在整个处理链的最前端：
protected void initChannel(Channel ch) throws Exception {
ch.pipeline().addLast(new MyChannelInboundHandler1());
ch.pipeline().addLast(new MyChannelInboundHandler2());
ch.pipeline().addFirst(new MyChannelOutboundHandler1());
}
二、完整示例代码：
1.MyChannelInboundHandler1
package cn.edu.tju; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.SimpleChannelInboundHandler; import io.netty.util.CharsetUtil; public class MyChannelInboundHandler1 extends SimpleChannelInboundHandler
2.MyChannelInboundHandler2
package cn.edu.tju; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.SimpleChannelInboundHandler; import io.netty.util.CharsetUtil; public class MyChannelInboundHandler2 extends SimpleChannelInboundHandler
3.MyChannelOutboundHandler1
package cn.edu.tju;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelOutboundHandlerAdapter;
import io.netty.channel.ChannelPromise;
import io.netty.util.CharsetUtil;
public class MyChannelOutboundHandler1 extends ChannelOutboundHandlerAdapter {
public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
String result=(String)msg;
System.out.println("MyChannelOutboundHandler1 received: "+result);
ByteBuf byteBuf= Unpooled.copiedBuffer(result.getBytes());
ctx.write(byteBuf, promise);
}
}
4.NettyServer
package cn.edu.tju;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
public class NettyServer {
public static void main(String[] args) {
EventLoopGroup bossGroup=new NioEventLoopGroup(1);
EventLoopGroup workerGroup=new NioEventLoopGroup();
try{
ServerBootstrap serverBootstrap=new ServerBootstrap();
serverBootstrap.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class);
serverBootstrap.childHandler(new ChannelInitializer() {
@Override
protected void initChannel(Channel ch) throws Exception {
ch.pipeline().addLast(new MyChannelInboundHandler1());
ch.pipeline().addLast(new MyChannelInboundHandler2());
ch.pipeline().addLast(new MyChannelOutboundHandler1());
}
});
serverBootstrap.bind(9095);
}catch (Exception ex){
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
三、启动并测试：
