第1章 Netty服务端意外退出案例
在使用Netty进行服务端程序开发时，主要涉及端口监听、EventLoop线程池创建、NioServerSocketChannel和ChannelPipeline初始化等。初学者如果对服务端相关类库的工作原理和用法不熟悉，则会导致程序启动或者退出发生问题。
1.1 Netty服务端意外退出问题
案例1 通过阻塞方式绑定监听端口，启动服务端之后，没发生任何异常，程序退出
代码如下：
try {
ServerBootStrap b = new ServerBootStrap();
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 100)
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline p = ch.pipeline();
p.addLast(new LoggingHandler(LogLevel.INFO));
}
});
b.bind(18080).sync(); // 用同步方式绑定服务端监听端口
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
案例2 对案例1进行排查时，发现没有监听Close Future，于是对代码进行修改，还是会发生服务器套接字直接关闭、进程退出的问题
代码如下：
try {
ServerBootStrap b = new ServerBootStrap();
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 100)
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline p = ch.pipeline();
p.addLast(new LoggingHandler(LogLevel.INFO));
}
});
ChannelFuture f = b.bind(18080).sync(); // 用同步方式绑定服务端监听端口
f.channel().closeFuture().addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
// 业务逻辑处理代码，此处省略
logger.info(future.channel().toString() + " 链路关闭");
}
});
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}