Netty学习笔记（一）
Netty是一个高性能的NIO框架，相比与IO编程需要编写大量的代码，Netty的使用更加简单。Netty的主要功能是负责网络传输，dubbo，rocket MQ以及elasticsearch中都采用Netty做为网络传输框架。
Netty的特性（以下特性来自百度，但是我感觉对于开发者来时主要还是用起来比较简单。。。。。。）
1.设计
针对多种传输类型的统一接口 - 阻塞和非阻塞
简单但更强大的线程模型
真正的无连接的数据报套接字支持
链接逻辑支持复用
2.易用性
大量的 Javadoc 和 代码实例
除了在 JDK 1.6 + 额外的限制。(一些特征是只支持在Java 1.7 +。可选的功能可能有额外的限制。)
3.性能
比核心 Java API 更好的吞吐量，较低的延时
资源消耗更少，这个得益于共享池和重用
减少内存拷贝
4.健壮性
消除由于慢，快，或重载连接产生的 OutOfMemoryError
消除经常发现在 NIO 在高速网络中的应用中的不公平的读/写比
5.安全
完整的 SSL / TLS 和 StartTLS 的支持
行在受限的环境例如 Applet 或 OSGI
6.社区
发布的更早和更频繁
社区驱动
服务端：
public class Server {
public static void main(String[] args) throws Exception{
//1 创建线两个程组
//一个是用于处理服务器端接收客户端连接的
//一个是进行网络通信的（网络读写的）
EventLoopGroup pGroup = new NioEventLoopGroup();
EventLoopGroup cGroup = new NioEventLoopGroup();
//2 创建辅助工具类，用于服务器通道的一系列配置
ServerBootstrap b = new ServerBootstrap();
b.group(pGroup, cGroup)//绑定俩个线程组
.channel(NioServerSocketChannel.class)//指定NIO的模式
.option(ChannelOption.SO_BACKLOG, 1024)//设置tcp缓冲区
//设置日志
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new ChannelInitializer() {
protected void initChannel(SocketChannel sc) throws Exception {
sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
//客户端与服务端在3s内没有任何通信则关闭响应通道 节省服务器资源（客户端服务端都需要配置）
sc.pipeline().addLast(new ReadTimeoutHandler(3));
//3 在这里配置具体数据接收方法的处理
sc.pipeline().addLast(new ServerHandler());
}
});
//4 进行绑定
ChannelFuture cf1 = b.bind(8765).sync();
//ChannelFuture cf2 = b.bind(8766).sync();
//5 等待关闭
cf1.channel().closeFuture().sync();
//cf2.channel().closeFuture().sync();
pGroup.shutdownGracefully();
cGroup.shutdownGracefully();
}
}
public class ServerHandler extends ChannelHandlerAdapter{
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
Request request = (Request)msg;
System.out.println("Server : " + request.getId() + ", " + request.getName() + ", " + request.getRequestMessage());
Response response = new Response();
response.setId(request.getId());
response.setName("response" + request.getId());
response.setResponseMessage("响应内容" + request.getId());
ctx.writeAndFlush(response);//.addListener(ChannelFutureListener.CLOSE);监听响应成功后断开通道短链接方式
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
}
}
客户端：
public class Client {
private static class SingletonHolder {
static final Client instance = new Client();
}
public static Client getInstance(){
return SingletonHolder.instance;
}
private EventLoopGroup group;
private Bootstrap b;
private ChannelFuture cf ;
private Client(){
group = new NioEventLoopGroup();
b = new Bootstrap();
b.group(group)
.channel(NioSocketChannel.class)
.handler(new LoggingHandler(LogLevel.INFO))
.handler(new ChannelInitializer() {
@Override
protected void initChannel(SocketChannel sc) throws Exception {
//通过JBOSS的Marshalling进行编码解码
sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
//客户端与服务端在3s内没有任何通信则关闭响应通道 节省服务器资源
sc.pipeline().addLast(new ReadTimeoutHandler(3));
//
sc.pipeline().addLast(new ClientHandler());
}
});
}
public void connect(){
try {
this.cf = b.connect("127.0.0.1", 8765).sync();
System.out.println("远程服务器已经连接, 可以进行数据交换..");
} catch (Exception e) {
e.printStackTrace();
}
}
public ChannelFuture getChannelFuture(){
if(this.cf == null){
this.connect();
}
if(!this.cf.channel().isActive()){
this.connect();
}
return this.cf;
}
public static void main(String[] args) throws Exception{
final Client c = Client.getInstance();
//c.connect();
ChannelFuture cf = c.getChannelFuture();
for(int i = 1; i <= 3; i++ ){
Request request = new Request();
request.setId("" + i);
request.setName("pro" + i);
request.setRequestMessage("数据信息" + i);
cf.channel().writeAndFlush(request);
TimeUnit.SECONDS.sleep(4);
}
cf.channel().closeFuture().sync();
//通过new一个子线程来重新连接服务端
new Thread(new Runnable() {
@Override
public void run() {
try {
System.out.println("进入子线程...");
ChannelFuture cf = c.getChannelFuture();
System.out.println(cf.channel().isActive());
System.out.println(cf.channel().isOpen());
//再次发送数据
Request request = new Request();
request.setId("" + 4);
request.setName("pro" + 4);
request.setRequestMessage("数据信息" + 4);
cf.channel().writeAndFlush(request);
cf.channel().closeFuture().sync();
System.out.println("子线程结束.");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
System.out.println("断开连接,主线程结束..");
}
}
public class ClientHandler extends ChannelHandlerAdapter{
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
try {
Response resp = (Response)msg;
System.out.println("Client : " + resp.getId() + ", " + resp.getName() + ", " + resp.getResponseMessage());
} finally {
ReferenceCountUtil.release(msg);
}
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
}
}
Marshalling工厂：
public final class MarshallingCodeCFactory {
/**
* 创建Jboss Marshalling×××MarshallingDecoder
* @return MarshallingDecoder
*/
public static MarshallingDecoder buildMarshallingDecoder() {
//首先通过Marshalling工具类的精通方法获取Marshalling实例对象 参数serial标识创建的是java序列化工厂对象。
final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
//创建了MarshallingConfiguration对象，配置了版本号为5
final MarshallingConfiguration configuration = new MarshallingConfiguration();
configuration.setVersion(5);
//根据marshallerFactory和configuration创建provider
UnmarshallerProvider provider = new DefaultUnmarshallerProvider(marshallerFactory, configuration);
//构建Netty的MarshallingDecoder对象，俩个参数分别为provider和单个消息序列化后的最大长度
MarshallingDecoder decoder = new MarshallingDecoder(provider, 1024);
return decoder;
}
/**
* 创建Jboss Marshalling编码器MarshallingEncoder
* @return MarshallingEncoder
*/
public static MarshallingEncoder buildMarshallingEncoder() {
final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
final MarshallingConfiguration configuration = new MarshallingConfiguration();
configuration.setVersion(5);
MarshallerProvider provider = new DefaultMarshallerProvider(marshallerFactory, configuration);
//构建Netty的MarshallingEncoder对象，MarshallingEncoder用于实现序列化接口的POJO对象序列化为二进制数组
MarshallingEncoder encoder = new MarshallingEncoder(provider);
return encoder;
}
}