本文是学习Netty的第一篇文章，主要对Netty的Server和Client间的通讯机制进行验证。
Server与Client建立连接后，会执行以下的步骤：
1.Client向Server发送消息：Are you ok?
2.Server接收客户端发送的消息，并打印出来。
3.Server端向客户端发送消息：I am ok!
4.Client接收Server端发送的消息，并打印出来，通讯结束。
涉及到的类有4个：
1.HelloServer ：server类，启动Netty server
2.HelloServerInHandler：server的handler，接收客户端消息，并向客户端发送消息
3.HelloClient：client类，建立于Netty server的连接
4.HelloClientIntHandler：client的handler，接收server端的消息，并向服务端发送消息
HelloServer.java
package com.bijian.netty.server;
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 HelloServer {
public void start(int port) throws Exception {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
// 注册handler
ch.pipeline().addLast(new HelloServerInHandler());
}
}).option(ChannelOption.SO_BACKLOG, 128).childOption(ChannelOption.SO_KEEPALIVE, true);
ChannelFuture f = b.bind(port).sync();
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {
HelloServer server = new HelloServer();
server.start(8000);
}
}
HelloServerInHandler.java
package com.bijian.netty.server;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
// 该handler是InboundHandler类型
public class HelloServerInHandler extends ChannelInboundHandlerAdapter {
private static Log logger = LogFactory.getLog(HelloServerInHandler.class);
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
logger.info("HelloServerInHandler.channelRead");
ByteBuf result = (ByteBuf) msg;
byte[] result1 = new byte[result.readableBytes()];
// msg中存储的是ByteBuf类型的数据，把数据读取到byte[]中
result.readBytes(result1);
String resultStr = new String(result1);
// 接收并打印客户端的信息
System.out.println("Client said:" + resultStr);
// 释放资源，这行很关键
result.release();
// 向客户端发送消息
String response = "I am ok!";
// 在当前场景下，发送的数据必须转换成ByteBuf数组
ByteBuf encoded = ctx.alloc().buffer(4 * response.length());
encoded.writeBytes(response.getBytes());
ctx.write(encoded);
ctx.flush();
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
ctx.flush();
}
}
HelloClient.java
package com.bijian.netty.client;
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 HelloClient {
public void connect(String host, int port) throws Exception {
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
b.group(workerGroup).channel(NioSocketChannel.class).option(ChannelOption.SO_KEEPALIVE, true)
.handler(new ChannelInitializer() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new HelloClientIntHandler());
}
});
// Start the client.
ChannelFuture f = b.connect(host, port).sync();
// Wait until the connection is closed.
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {
HelloClient client = new HelloClient();
client.connect("127.0.0.1", 8000);
}
}
HelloClientIntHandler.java
package com.bijian.netty.client;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
public class HelloClientIntHandler extends ChannelInboundHandlerAdapter {
private static Log logger = LogFactory.getLog(HelloClientIntHandler.class);
// 接收server端的消息，并打印出来
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
logger.info("HelloClientIntHandler.channelRead");
ByteBuf result = (ByteBuf) msg;
byte[] result1 = new byte[result.readableBytes()];
result.readBytes(result1);
System.out.println("Server said:" + new String(result1));
result.release();
}
// 连接成功后，向server发送消息
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
logger.info("HelloClientIntHandler.channelActive");
String msg = "Are you ok?";
ByteBuf encoded = ctx.alloc().buffer(4 * msg.length());
encoded.writeBytes(msg.getBytes());
ctx.write(encoded);
ctx.flush();
}
}
通过上面简单的实例可以发现：
1.在没有任何encoder、decoder的情况下，Netty发送接收数据都是按照ByteBuf的形式，其它形式都是不合法的。
2.接收发送数据操作都是通过handler实现的，handler在netty中占据了非常重要的位置。
3.netty的handler是基于事件触发的，例如当client连接server成功后，client中的HelloClientIntHandler的channelActive方法会自动调用。
文章来源：http://blog.csdn.net/u013252773/article/details/21046697