实现一个功能,客户端和服务器 轮流对一个数加+1
服务器
public class Server {
public static void main(String[] args) {
NioEventLoopGroup boss=new NioEventLoopGroup(1);
NioEventLoopGroup worker=new NioEventLoopGroup(3);
try {
final ServerBootstrap server=new ServerBootstrap();
server.group(boss,worker).channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new ServerHandler());
}
});
ChannelFuture future = server.bind(8881).sync();
future.channel().closeFuture().sync();
}catch (Exception e){
e.printStackTrace();
}
finally {
boss.shutdownGracefully();
worker.shutdownGracefully();
}
}
}
服务器handler
netty ChannelHandler 类似 spring mvc的filter,使用的是责任链模式,可以对客户端传来的数据进行层层解析,解码等操作。
在没有任何特殊操作下,默认传递在责任中的对象是ByteBuf
public class ServerHandler extends ChannelInboundHandlerAdapter {
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {//msg 其实就是个ByteBuf 对象
ByteBuf buf=(ByteBuf) msg;
int i = buf.readInt();
System.out.println("服务器收到客户端消息"+ctx.channel().remoteAddress()+" "+i);
ByteBuf newbuf=ctx.alloc().buffer(1024);
newbuf.writeInt(i+1);
ctx.writeAndFlush(newbuf);
buf.release();
}
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
System.out.println("channel active");
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
客户端
public class Client {
public static void main(String[] args) {
NioEventLoopGroup boss=new NioEventLoopGroup(1);
try {
final Bootstrap client=new Bootstrap();
client.group(boss).channel(NioSocketChannel.class)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new ClientHandler());
}
});
ChannelFuture future = client.connect("127.0.0.1",8881).sync();
future.channel().closeFuture().sync();
}catch (Exception e){
e.printStackTrace();
}
finally {
boss.shutdownGracefully();
}
}
}
客户端handlr
public class ClientHandler extends SimpleChannelInboundHandler {
@Override
protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
ByteBuf buf=(ByteBuf)msg;
int i=buf.readInt();
System.out.println("客服端收到服务器"+ctx.channel().remoteAddress()+"---> "+i);
Thread.sleep(2000);
ByteBuf newbuf = ctx.alloc().buffer(1024);
newbuf.writeInt(i+1);
ctx.writeAndFlush(newbuf);
}
@Override
public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
System.out.println("连接服务器成功");
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
ByteBuf buffer = ctx.alloc().buffer(1024);
buffer.writeInt(1);
ctx.writeAndFlush(buffer);
}
}
一开始很疑惑,channelRead0(ChannelHandlerContext ctx, Object msg) 方法里的msg 到底是个什么对象?
在添加其它handler之后,比如一个StringDecode,netty会自动的把ByteBuf里的字节转String,并传递在Object对象中。这是Object就是一个String。
翻了下源码,还是很清晰的
在ChannelHandlerContext 接口中有一个fireChannelRead 方法,这个方法的解释如下
ChannelHandlerContext fireChannelRead(java.lang.Object msg)
Description copied from interface: ChannelInboundInvoker
A Channel received a message. This will result in having the ChannelInboundHandler.channelRead(ChannelHandlerContext, Object) method called of the next ChannelInboundHandler contained in the ChannelPipeline of the Channel.
Specified by:
fireChannelRead in interface ChannelInboundInvoker
简单来就是会调用handler 责任链的下一个处理类。同过fireChannelRead方法,可以给下一个责任链传递一个对象msg,这个msg会传递到下一个处理类的 ChannelRead方法上。例如,StringDecode把ByteBuf转为一个String对象msg,在调用fireChannelRead(msg),就把这个String传到下一个handler去了。
channelRead0也是同样的意思
netty是基于nio的框架,要是理解了nio,其实操作起来也不是很费劲。
原文地址:https://www.cnblogs.com/duangL/p/11629840.html