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io.netty.channel.ChannelInitializer是一个特殊的ChannelInboundHandler。它的主要作用是向 Channel对应的ChannelPipeline中增加ChannelHandler。执行完ChannelInitializer的initChannel(C ch)函数以后#xff0c;ChannelInitializer就会从ChannelPipeline自动删除自己…说明
io.netty.channel.ChannelInitializer是一个特殊的ChannelInboundHandler。它的主要作用是向 Channel对应的ChannelPipeline中增加ChannelHandler。执行完ChannelInitializer的initChannel(C ch)函数以后ChannelInitializer就会从ChannelPipeline自动删除自己防止重复进入。 一般是通过Bootstrap.handler(ChannelHandler) 、ServerBootstrap.childHandler(ChannelHandler)的方式分别在客户端、服务端中将ChannelInitializer这个ChannelHandler增加到ChannelPipeline中。
示例
思路
我们来验证下ChannelInitializer是否会被自动删除。我们在ChannelInitializer的initChannel(C ch)函数末尾打印出来当前ChannelPipeline中已经添加的ChannelHandler名称在Channel连接成功以后再打印出来当前ChannelPipeline中已经添加的ChannelHandler名称两者对照下就能看出来是否被自动删除了。
代码片段
package com.thb.power.terminal;import java.io.BufferedReader;
import java.io.InputStreamReader;import com.thb.power.packet.register.RegisterRequestPacket;import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;/*** 主函数* author thb**/
public class Terminal {// 要连接的服务端的host static final String HOST System.getProperty(host, 127.0.0.1); // 要连接的服务端的端口号 static final int PORT Integer.parseInt(System.getProperty(port, 22335));public static void main(String[] args) throws Exception {// 配置客户端EventLoopGroup group new NioEventLoopGroup();try {Bootstrap b new Bootstrap();b.group(group).channel(NioSocketChannel.class).option(ChannelOption.TCP_NODELAY, true).handler(new TerminalInitializer());// 启动客户端Channel ch b.connect(HOST, PORT).sync().channel(); // 查看ChannelPipeline添加的ChannelHandler名称System.out.println(after channel connected:);for (String name : ch.pipeline().names()) {System.out.println(handler name: name);} ChannelFuture lastWriteFuture null;BufferedReader in new BufferedReader(new InputStreamReader(System.in));System.out.println(please input(register):);for (;;) {String line in.readLine();if (line null) {break;} // 如果用户输入register表示命令客户端发送注册请求给服务器if (line.toLowerCase().equals(register)) {RegisterRequestPacket registerRequest new RegisterRequestPacket();// 返回的ByteBuf存放着注册请求的数据ByteBuf buf registerRequest.build(ch);lastWriteFuture ch.writeAndFlush(buf); }}if (lastWriteFuture ! null) {lastWriteFuture.sync();}} finally {// 关闭event loop以便终止所有的线程group.shutdownGracefully();}}}// ChannelInitializer的子类
package com.thb.power.terminal;import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;public class TerminalInitializer extends ChannelInitializerSocketChannel {Overridepublic void initChannel(SocketChannel ch) throws Exception {ChannelPipeline p ch.pipeline();p.addLast(new LoggingHandler(LogLevel.INFO));// 查看ChannelPipeline添加的ChannelHandler名称System.out.println(in initChannel(SocketChannel ch) method of TerminalInitializer:);for (String name : ch.pipeline().names()) {System.out.println(handler name: name);} }
}运行输出 从上面输出可以看出ChannelInitializer开始被添加到ChannelPipeline中后来又被自动删除了。
