Netty之BIO(同步阻塞IO)、PIO(偽非同步阻塞IO)、NIO(非同步非阻塞IO)、AIO(非同步非阻塞IO)、Netty
阿新 • • 發佈:2019-01-24
學習書籍:Netty權威指南
多種IO方式的比較:
1、BIO(同步阻塞IO)
使用ServerSocket繫結IP地址和監聽埠,客戶端發起連線,通過三次握手建立連線,用socket來進行通訊,通過輸入輸出流的方式來進行同步阻塞的通訊
每次客戶端發起連線請求,都會啟動一個執行緒
執行緒數量:客戶端併發訪問數為1:1,由於執行緒是JAVA虛擬機器中非常寶貴的資源,一旦執行緒數急劇增加,系統性能會急劇下降,導致執行緒棧溢位,建立新的執行緒失敗,並最終導致宕機
所以在JDK1.4之前,人們想到了一種方法,即PIO方式
2、PIO(偽非同步阻塞IO)
使用執行緒池來處理客戶端的請求
客戶端個數:執行緒池最大執行緒數=M:N,其中M遠大於N
在read和write的時候,還是IO阻塞的,只是把每個執行緒交由執行緒池來控制管理
3、NIO(非同步阻塞IO)
用NIO方式處理IO
使用多路複用器Selector來輪詢每個通道Channel,當通道中有事件時就通知處理,不會阻塞
使用相當複雜
4、AIO(真正的非同步非阻塞IO)
NIO2.0引入了新的非同步通道的概念,不需要使用多路複用器(Selector)對註冊通道進行輪詢即可實現非同步讀寫,從而簡化了NIO程式設計模型
使用Netty框架進行程式設計步驟
1、構建事件處理池
2、使用載入程式關聯事件處理池、通道、事件處理器
3、繫結埠服務
4、等待操作完成
5、關閉事件處理池
幾種IO的功能和特性對比
按照書上的例子碼了一遍:
服務端:
服務端處理器:import io.netty.bootstrap.ServerBootstrap; import io.netty.channel.ChannelFuture; import io.netty.channel.ChannelInitializer; import io.netty.channel.ChannelOption; import io.netty.channel.EventLoopGroup; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioServerSocketChannel; public class NettyServer { public void bind(int port) throws Exception { EventLoopGroup bossGroup = new NioEventLoopGroup(); EventLoopGroup workGroup = new NioEventLoopGroup(); try { ServerBootstrap b = new ServerBootstrap(); b.group(bossGroup, workGroup).channel(NioServerSocketChannel.class) .option(ChannelOption.SO_BACKLOG, 1024) .childHandler(new ChildChannelHandler()); // 繫結埠,同步等待成功 ChannelFuture f = b.bind(port).sync(); // 等待服務端監聽埠關閉 f.channel().closeFuture().sync(); } catch (Exception e) { // TODO: handle exception } finally { // 優雅退出,釋放執行緒池資源 bossGroup.shutdownGracefully(); workGroup.shutdownGracefully(); } } private class ChildChannelHandler extends ChannelInitializer<SocketChannel> { @Override protected void initChannel(SocketChannel ch) throws Exception { ch.pipeline().addLast(new NettyServerHandle()); } } public static void main(String[] args) throws Exception { int port = 8080; if (args != null && args.length > 0) { try { port = Integer.valueOf(args[0]); } catch (Exception e) { e.printStackTrace(); } } new NettyServer().bind(port); } }
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
public class NettyServerHandle extends ChannelHandlerAdapter {
public void channelRead(ChannelHandlerContext ctx, Object msg)
throws Exception {
ByteBuf buf = (ByteBuf) msg;
byte[] req = new byte[buf.readableBytes()];
buf.readBytes(req);
String body = new String(req, "UTF-8");
System.out.println("The time server receive order:" + body);
String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new java.util.Date(
System.currentTimeMillis()).toString() : "BAD ORDER";
ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
ctx.write(resp);
}
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
ctx.flush();
}
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
ctx.close();
}
}
客戶端:
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
public class NettyClient {
public void connect(int port, String host) throws Exception {
// 1、建立執行緒池
EventLoopGroup group = new NioEventLoopGroup();
try {
// 2、使用引導器關聯執行緒池、通道、通達處理器、設定執行引數
Bootstrap b = new Bootstrap();
b.group(group).channel(NioSocketChannel.class)
.option(ChannelOption.TCP_NODELAY, true)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch)
throws Exception {
ch.pipeline().addLast(new NettyClientHandle());
}
});
// 發起非同步連線操作 3、繫結埠同步操作
ChannelFuture f = b.connect(host, port).sync();
// 4、監聽埠關閉
f.channel().closeFuture().sync();
} catch (Exception e) {
// TODO: handle exception
} finally {
// 優雅退出,釋放NIO執行緒組 5、釋放資源
group.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {
int port = 8080;
if (args != null && args.length > 0) {
try {
port = Integer.valueOf(args[0]);
} catch (Exception e) {
e.printStackTrace();
}
}
new NettyClient().connect(port, "127.0.0.1");
}
}
客戶端處理器:
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import java.util.logging.Logger;
public class NettyClientHandle extends ChannelHandlerAdapter {
private static final Logger logger = Logger
.getLogger(NettyClientHandle.class.getName());
private final ByteBuf firstMessage;
public NettyClientHandle() {
byte[] req = "QUERY TIME ORDER".getBytes();
firstMessage = Unpooled.buffer(req.length);
firstMessage.writeBytes(req);
}
public void channelActive(ChannelHandlerContext ctx) {
ctx.writeAndFlush(firstMessage);
}
public void channelRead(ChannelHandlerContext ctx, Object msg)
throws Exception {
ByteBuf buf = (ByteBuf) msg;
byte[] req = new byte[buf.readableBytes()];
buf.readBytes(req);
String body = new String(req, "UTF-8");
System.out.println("Now is:" + body);
}
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
// 釋放資源
logger.warning("Unexpected exception from downstream:"
+ cause.getMessage());
ctx.close();
}
}