Java学习笔记—开源框架Netty的简单使用

1:什么是Netty

Netty是由JBOSS提供的一个java开源框架。Netty提供异步的、事件驱动的网络应用程序框架和工具,用以快速开发高性能、高可靠性的网络服务器和客户端程序。

Netty是一个基于NIO的客户,服务器端编程框架,使用Netty可以确保你快速和简单的开发出一个网络应用,例如实现了某种协议的客户,服务端应用。

Netty相当简化和流线化了网络应用的编程开发过程,例如,TCP和UDP的socket服务开发。

Netty是一个吸收了多种协议的实现经验,这些协议包括FTP,SMTP,HTTP,各种二进制,文本协议,并经过相当精心设计的项目,最终,Netty 成功的找到了一种方式,在保证易于开发的同时还保证了其应用的性能,稳定性和伸缩性。

官网地址:http://netty.io/index.html

2:Netty的特性

设计

统一的API,适用于不同的协议(阻塞和非阻塞)

基于灵活、可扩展的事件驱动模型

高度可定制的线程模型

可靠的无连接数据Socket支持(UDP)

性能

更好的吞吐量,低延迟

更省资源

尽量减少不必要的内存拷贝

安全

完整的SSL/TLS和STARTTLS的支持

能在Applet与Android的限制环境运行良好

健壮性

不再因过快、过慢或超负载连接导致OutOfMemoryError

不再有在高速网络环境下NIO读写频率不一致的问题

易用

完善的JavaDoc,用户指南和样例

简洁简单

3:Netty基本架构图

4:简单例子(本文中netty的版本是netty-all-4.0.29)

去官网下载jar http://netty.io/index.html 或者可以使用maven

io.netty netty-all 4.0.29.Final

以HTTP协议举例

service代码

package com.demo.http;

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;

import io.netty.handler.codec.http.HttpRequestDecoder;

import io.netty.handler.codec.http.HttpResponseEncoder;

public class HttpServer {

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 {

// server端发送的是httpResponse,所以要使用HttpResponseEncoder进行编码

ch.pipeline().addLast(new HttpResponseEncoder());

// server端接收到的是httpRequest,所以要使用HttpRequestDecoder进行解码

ch.pipeline().addLast(new HttpRequestDecoder());

ch.pipeline().addLast(new HttpServerInboundHandler());

}

}).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 {

HttpServer server = new HttpServer();

System.out.println("Http Server listening on 8844 ...");

server.start(8844);

}

}

package com.demo.http;

import static io.netty.handler.codec.http.HttpHeaders.Names.CONNECTION;

import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_LENGTH;

import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_TYPE;

import static io.netty.handler.codec.http.HttpResponseStatus.OK;

import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;

import io.netty.buffer.ByteBuf;

import io.netty.buffer.Unpooled;

import io.netty.channel.ChannelHandlerContext;

import io.netty.channel.ChannelInboundHandlerAdapter;

import io.netty.handler.codec.http.DefaultFullHttpResponse;

import io.netty.handler.codec.http.FullHttpResponse;

import io.netty.handler.codec.http.HttpContent;

import io.netty.handler.codec.http.HttpHeaders;

import io.netty.handler.codec.http.HttpHeaders.Values;

import io.netty.handler.codec.http.HttpRequest;

public class HttpServerInboundHandler extends ChannelInboundHandlerAdapter {

private HttpRequest request;

@Override

public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

if (msg instanceof HttpRequest) {

request = (HttpRequest) msg;

String uri = request.getUri();

System.out.println("Uri:" + uri);

}

if (msg instanceof HttpContent) {

HttpContent content = (HttpContent) msg;

ByteBuf buf = content.content();

System.out.println(buf.toString(io.netty.util.CharsetUtil.UTF_8));

buf.release();

String res = "www.ccblog.cn";

FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK,

Unpooled.wrappedBuffer(res.getBytes("UTF-8")));

response.headers().set(CONTENT_TYPE, "text/plain");

response.headers().set(CONTENT_LENGTH, response.content().readableBytes());

if (HttpHeaders.isKeepAlive(request)) {

response.headers().set(CONNECTION, Values.KEEP_ALIVE);

}

ctx.write(response);

ctx.flush();

}

}

public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

ctx.flush();

}

public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {

System.out.println(cause.getMessage());

ctx.close();

}

}

客户端访问

第一中执行上面的main方法后 在浏览器里面直接输入

http://127.0.0.1:8844/ 你可以看到 www.ccblog.cn 内容。

第二种采用java编写客户端

代码如下

package com.demo.http;

import io.netty.bootstrap.Bootstrap;

import io.netty.buffer.Unpooled;

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;

import io.netty.handler.codec.http.DefaultFullHttpRequest;

import io.netty.handler.codec.http.HttpHeaders;

import io.netty.handler.codec.http.HttpMethod;

import io.netty.handler.codec.http.HttpRequestEncoder;

import io.netty.handler.codec.http.HttpResponseDecoder;

import io.netty.handler.codec.http.HttpVersion;

import java.net.URI;

public class HttpClient {

public void connect(String host, int port) throws Exception {

EventLoopGroup workerGroup = new NioEventLoopGroup();

try {

Bootstrap b = new Bootstrap();

b.group(workerGroup);

b.channel(NioSocketChannel.class);

b.option(ChannelOption.SO_KEEPALIVE, true);

b.handler(new ChannelInitializer() {

@Override

public void initChannel(SocketChannel ch) throws Exception {

// 客户端接收到的是httpResponse响应,所以要使用HttpResponseDecoder进行解码

ch.pipeline().addLast(new HttpResponseDecoder());

// 客户端发送的是httprequest,所以要使用HttpRequestEncoder进行编码

ch.pipeline().addLast(new HttpRequestEncoder());

ch.pipeline().addLast(new HttpClientInboundHandler());

}

});

// Start the client.

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

URI uri = new URI("http://127.0.0.1:8844");

String msg = "Are you ok?";

DefaultFullHttpRequest request = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET,

uri.toASCIIString(), Unpooled.wrappedBuffer(msg.getBytes("UTF-8")));

// 构建http请求

request.headers().set(HttpHeaders.Names.HOST, host);

request.headers().set(HttpHeaders.Names.CONNECTION, HttpHeaders.Values.KEEP_ALIVE);

request.headers().set(HttpHeaders.Names.CONTENT_LENGTH, request.content().readableBytes());

// 发送http请求

f.channel().write(request);

f.channel().flush();

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

} finally {

workerGroup.shutdownGracefully();

}

}

public static void main(String[] args) throws Exception {

HttpClient client = new HttpClient();

client.connect("127.0.0.1", 8844);

}

}

package com.demo.http;

import io.netty.buffer.ByteBuf;

import io.netty.channel.ChannelHandlerContext;

import io.netty.channel.ChannelInboundHandlerAdapter;

import io.netty.handler.codec.http.HttpContent;

import io.netty.handler.codec.http.HttpHeaders;

import io.netty.handler.codec.http.HttpResponse;

public class HttpClientInboundHandler extends ChannelInboundHandlerAdapter {

@Override

public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

if (msg instanceof HttpResponse) {

HttpResponse response = (HttpResponse) msg;

System.out.println("CONTENT_TYPE:" + response.headers().get(HttpHeaders.Names.CONTENT_TYPE));

}

if (msg instanceof HttpContent) {

HttpContent content = (HttpContent) msg;

ByteBuf buf = content.content();

System.out.println(buf.toString(io.netty.util.CharsetUtil.UTF_8));

buf.release();

}

}

}

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