Netty学习笔记 10.2 Netty的handler链的调用机制
实例要求:
使用自定义的编码器和解码器来说明Netty的handler 调用机制
客户端发送long -> 服务器
服务端发送long -> 客户端
案例演示
- 结论
不论解码器handler 还是 编码器handler 即接收的消息类型必须与待处理的消息类型一致,否则该handler不会被执行
在解码器 进行数据解码时,需要判断 缓存区(ByteBuf)的数据是否足够 ,否则接收到的结果会期望结果可能不一致
MyByteToLongDecoder
package com.my.netty.inboundhandlerandoutboundhandler;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import java.util.List;
public class MyByteToLongDecoder extends ByteToMessageDecoder {
/**
*
* decode 会根据接收的数据,被调用多次, 直到确定没有新的元素被添加到list
* , 或者是ByteBuf 没有更多的可读字节为止
* 如果list out 不为空,就会将list的内容传递给下一个 channelinboundhandler处理, 该处理器的方法也会被调用多次
*
* @param ctx 上下文对象
* @param in 入站的 ByteBuf
* @param out List 集合,将解码后的数据传给下一个handler
* @throws Exception
*/
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
System.out.println("MyByteToLongDecoder 被调用");
//因为 long 8个字节, 需要判断有8个字节,才能读取一个long
if(in.readableBytes() >= 8) {
out.add(in.readLong());
}
}
}
MyLongToByteEncoder
package com.my.netty.inboundhandlerandoutboundhandler;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
public class MyLongToByteEncoder extends MessageToByteEncoder<Long> {
//编码方法
@Override
protected void encode(ChannelHandlerContext ctx, Long msg, ByteBuf out) throws Exception {
System.out.println("MyLongToByteEncoder encode 被调用");
System.out.println("msg=" + msg);
out.writeLong(msg);
}
}
MyClient
package com.my.netty.inboundhandlerandoutboundhandler;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
public class MyClient {
public static void main(String[] args) throws Exception{
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(group).channel(NioSocketChannel.class)
.handler(new MyClientInitializer()); //自定义一个初始化类
ChannelFuture channelFuture = bootstrap.connect("localhost", 7000).sync();
channelFuture.channel().closeFuture().sync();
}finally {
group.shutdownGracefully();
}
}
}
MyClient
package com.my.netty.inboundhandlerandoutboundhandler;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.util.CharsetUtil;
import java.nio.charset.Charset;
public class MyClientHandler extends SimpleChannelInboundHandler<Long> {
@Override
protected void channelRead0(ChannelHandlerContext ctx, Long msg) throws Exception {
System.out.println("服务器的ip=" + ctx.channel().remoteAddress());
System.out.println("收到服务器消息=" + msg);
}
//重写channelActive 发送数据
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
System.out.println("MyClientHandler 发送数据");
//ctx.writeAndFlush(Unpooled.copiedBuffer(""))
ctx.writeAndFlush(123456L); //发送的是一个long
//分析
//1. "abcdabcdabcdabcd" 是 16个字节
//2. 该处理器的前一个handler 是 MyLongToByteEncoder
//3. MyLongToByteEncoder 父类 MessageToByteEncoder
//4. 父类 MessageToByteEncoder
/*
public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
ByteBuf buf = null;
try {
if (acceptOutboundMessage(msg)) { //判断当前msg 是不是应该处理的类型,如果是就处理,不是就跳过encode
@SuppressWarnings("unchecked")
I cast = (I) msg;
buf = allocateBuffer(ctx, cast, preferDirect);
try {
encode(ctx, cast, buf);
} finally {
ReferenceCountUtil.release(cast);
}
if (buf.isReadable()) {
ctx.write(buf, promise);
} else {
buf.release();
ctx.write(Unpooled.EMPTY_BUFFER, promise);
}
buf = null;
} else {
ctx.write(msg, promise);
}
}
4. 因此我们编写 Encoder 是要注意传入的数据类型和处理的数据类型一致
*/
// ctx.writeAndFlush(Unpooled.copiedBuffer("abcdabcdabcdabcd",CharsetUtil.UTF_8));
}
}
MyClientInitializer
package com.my.netty.inboundhandlerandoutboundhandler;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
public class MyClientInitializer extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
//加入一个出站的handler 对数据进行一个编码
pipeline.addLast(new MyLongToByteEncoder());
//这时一个入站的解码器(入站handler )
//pipeline.addLast(new MyByteToLongDecoder());
pipeline.addLast(new MyByteToLongDecoder2());
//加入一个自定义的handler , 处理业务
pipeline.addLast(new MyClientHandler());
}
}
MyServer
package com.my.netty.inboundhandlerandoutboundhandler;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
public class MyServer {
public static void main(String[] args) throws Exception{
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class).childHandler(new MyServerInitializer()); //自定义一个初始化类
ChannelFuture channelFuture = serverBootstrap.bind(7000).sync();
channelFuture.channel().closeFuture().sync();
}finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
MyServerHandler
package com.my.netty.inboundhandlerandoutboundhandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
public class MyServerHandler extends SimpleChannelInboundHandler<Long> {
@Override
protected void channelRead0(ChannelHandlerContext ctx, Long msg) throws Exception {
System.out.println("从客户端" + ctx.channel().remoteAddress() + " 读取到long " + msg);
//给客户端发送一个long
ctx.writeAndFlush(98765L);
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
MyServerInitializer
package com.my.netty.inboundhandlerandoutboundhandler;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
public class MyServerInitializer extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();//一会下断点
//入站的handler进行解码 MyByteToLongDecoder
//pipeline.addLast(new MyByteToLongDecoder());
pipeline.addLast(new MyByteToLongDecoder2());
//出站的handler进行编码
pipeline.addLast(new MyLongToByteEncoder());
//自定义的handler 处理业务逻辑
pipeline.addLast(new MyServerHandler());
System.out.println("xx");
}
}