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netty 学习（1）

news 来源：原创 2024/9/20 14:22:21

摘要本文是学习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。

netty server client

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

一、先加入必要的类库：

二、HelloServer代码如下：

packagecom.yao.netty;

importio.netty.bootstrap.ServerBootstrap;

importio.netty.channel.ChannelFuture;

importio.netty.channel.ChannelInitializer;

importio.netty.channel.ChannelOption;

importio.netty.channel.EventLoopGroup;

importio.netty.channel.nio.NioEventLoopGroup;

importio.netty.channel.socket.SocketChannel;

importio.netty.channel.socket.nio.NioServerSocketChannel;

publicclass HelloServer {

publicvoid start(intport) throwsException {

EventLoopGroup bossGroup = newNioEventLoopGroup();

EventLoopGroup workerGroup = newNioEventLoopGroup();

try{

ServerBootstrap b = newServerBootstrap();

b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)

.childHandler(newChannelInitializer<SocketChannel>() {

@Override

publicvoid initChannel(SocketChannel ch)

throwsException {

// 注册handler

ch.pipeline().addLast(newHelloServerInHandler());

}

}).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();

}

publicstatic void main(String[] args) throwsException {

HelloServer server = newHelloServer();

server.start(8000);

}

三、 HelloServerInHandler代码如下：

packagecom.yao.netty;

importio.netty.buffer.ByteBuf;

importio.netty.channel.ChannelHandlerContext;

importio.netty.channel.ChannelInboundHandlerAdapter;

importorg.apache.commons.logging.Log;

importorg.apache.commons.logging.LogFactory;

// 该handler是InboundHandler类型

publicclass HelloServerInHandler extendsChannelInboundHandlerAdapter {

privatestatic Log logger = LogFactory.getLog(HelloServerInHandler.class);

@Override

publicvoid channelRead(ChannelHandlerContext ctx, Object msg)

throwsException {

logger.info("HelloServerInHandler.channelRead");

ByteBuf result = (ByteBuf) msg;

byte[] result1 = newbyte[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 = newString(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

publicvoid channelReadComplete(ChannelHandlerContext ctx) throwsException {

ctx.flush();

}

四、HelloClient代码如下：

packagecom.yao.netty;

importio.netty.bootstrap.Bootstrap;

importio.netty.channel.ChannelFuture;

importio.netty.channel.ChannelInitializer;

importio.netty.channel.ChannelOption;

importio.netty.channel.EventLoopGroup;

importio.netty.channel.nio.NioEventLoopGroup;

importio.netty.channel.socket.SocketChannel;

importio.netty.channel.socket.nio.NioSocketChannel;

publicclass HelloClient {

publicvoid connect(String host, intport) throwsException {

EventLoopGroup workerGroup = newNioEventLoopGroup();

try{

Bootstrap b = newBootstrap();

b.group(workerGroup).channel(NioSocketChannel.class).option(ChannelOption.SO_KEEPALIVE,true)

.handler(newChannelInitializer<SocketChannel>() {

@Override

publicvoid initChannel(SocketChannel ch) throwsException {

ch.pipeline().addLast(newHelloClientIntHandler());

}

});

// Start the client.

ChannelFuture f = b.connect(host, port).sync();

// Wait until the connection is closed.

f.channel().closeFuture().sync();

}finally{

workerGroup.shutdownGracefully();

}

publicstatic void main(String[] args) throwsException {

HelloClient client = newHelloClient();

client.connect("127.0.0.1",8000);

}

五、 HelloClientIntHandler代码如下：

packagecom.yao.netty;

importio.netty.buffer.ByteBuf;

importio.netty.channel.ChannelHandlerContext;

importio.netty.channel.ChannelInboundHandlerAdapter;

importorg.apache.commons.logging.Log;

importorg.apache.commons.logging.LogFactory;

publicclass HelloClientIntHandler extendsChannelInboundHandlerAdapter {

privatestatic Log logger = LogFactory.getLog(HelloClientIntHandler.class);

// 接收server端的消息，并打印出来

@Override

publicvoid channelRead(ChannelHandlerContext ctx, Object msg) throwsException {

logger.info("HelloClientIntHandler.channelRead");

ByteBuf result = (ByteBuf) msg;

byte[] result1 = newbyte[result.readableBytes()];

result.readBytes(result1);

System.out.println("Server said:" + newString(result1));

result.release();

}

// 连接成功后，向server发送消息

@Override

publicvoid channelActive(ChannelHandlerContext ctx) throwsException {

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();

}

六、还有log4j.xml文件：

<?xmlversion="1.0"?>

<!DOCTYPElog4j:configuration SYSTEM "log4j.dtd">

<log4j:configurationxmlns:log4j="http://jakarta.apache.org/log4j/">

<appendername="CONSOLE"class="org.apache.log4j.ConsoleAppender">

<layoutclass="org.apache.log4j.PatternLayout">

<paramname="ConversionPattern"value="[%-5p] [%d] [%t] [%c] %m%n"/>

</layout>

</appender>

<appendername="FILE"class="org.apache.log4j.DailyRollingFileAppender">

<paramname="File"value="./log/netty.log"/>

<layoutclass="org.apache.log4j.PatternLayout">

<paramname="ConversionPattern"value="[%-5p] [%d] [%t] [%c] %m%n"/>

</layout>

</appender>

<appendername="FILE_ERR"class="org.apache.log4j.DailyRollingFileAppender">

<paramname="File"value="./log/netty_err.log"/>

<paramname="Threshold"value="ERROR"/>

<layoutclass="org.apache.log4j.PatternLayout">

<paramname="ConversionPattern"value="[%-5p] [%d] [%t] [%c] %m%n"/>

</layout>

</appender>

<loggername="io.netty"additivity="false">

<levelvalue="INFO,DEBUG"/>

<appender-refref="FILE"/>

<appender-refref="FILE_ERR"/>

<appender-refref="CONSOLE"/>

</logger>

<loggername="com.yao"additivity="false">

<levelvalue="INFO,DEBUG"/>

<appender-refref="FILE"/>

<appender-refref="FILE_ERR"/>

<appender-refref="CONSOLE"/>

</logger>

<root>

<levelvalue="debug"/>

<appender-refref="FILE"/>

<appender-refref="CONSOLE"/>

<appender-refref="FILE_ERR"/>

</root>

</log4j:configuration>

总结：
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。