netty 概览与hello world(一)

2019-08-25 本文已影响0人 kkkkky

netty概览

Netty是由JBOSS提供的一个java开源框架。

Netty is an asynchronous event-driven network application framework
for rapid development of maintainable high performance protocol servers & clients.

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。

也就是说，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相当于简化和流线化了网络应用的编程开发过程，例如：基于TCP和UDP的socket服务开发。

netty版本

目前为止netty的最新版本是netty4,在2019-08-13发布的4.1.39.Final。

为什么netty5被废弃了。

作者的声明与讨论

After talking with @Scottmitch and also with @nmittler I would like to propose "dropping" current master and so not release any new 5.0 version for now.

The major change of using a ForkJoinPool increases complexity and has not
demonstrated a clear performance benefit. Also keeping all the branches in sync is quite some work without a real need for it as there is nothin in current master which I think justifies a new major release.

Things that we should investigate to prepare for this change:

Deprecate exceptionCaught in ChannelHandler, only expose it in ChannelInboundHandler

Expose EventExecutorChooser from MultithreadEventExecutorGroup to allow the user more flexibility to choose next EventLoop

Add another method to be able to send user events both ways in the pipeline. (#4378)

Please chime in here and let me / us hear any concerns.

netty5中使用了ForkJoinPool，增加了代码的复杂度，但是对性能的改善却不明显。
多个分支的代码同步的工作量是很大的。
作者觉得当下还不到发布一个新版本的时候。
在发布版本之前，还有更多的问题需要调查一下。

hello world

创建一个java工程，引入netty最新的jar包，本人使用gradle创建。

dependencies {
    compile(
            "io.netty:netty-all:4.1.39.Final"
    )
}

创建testServer，bossGroup获取连接，并把连接分发给workerGroup

public class TestServer {
    public static void main(String[] args) throws InterruptedException {
        // bossGroup 获取连接 把连接分发给workerGroup
        NioEventLoopGroup bossGroup = new NioEventLoopGroup();
        NioEventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            //启动服务
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            //TestServerinitializer 自定义子处理器
            serverBootstrap.group(bossGroup, workerGroup)
              .channel(NioServerSocketChannel.class)
              .childHandler(new TestServerinitializer());
            ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }

    }
}

创建 TestServerinitializer

public class TestServerinitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast("httpServerCoder", new HttpServerCodec());
        pipeline.addLast("testHttpServerHandler",new TestHttpServerHandler());
    }
}

创建 testHttpServerHandler 负责读取客户端内容并设置返回报文

public class TestHttpServerHandler extends SimpleChannelInboundHandler<HttpObject> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception {
        ByteBuf content = Unpooled.copiedBuffer("hello world", CharsetUtil.UTF_8);
        DefaultHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1,
             HttpResponseStatus.OK, content);
        response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain");
        response.headers().set(HttpHeaderNames.CONTENT_LENGTH, content.readableBytes());
        ctx.writeAndFlush(response);
    }
}

运行testServer，用curl调用。

curl "http://localhost:8899"

返回结果

hello world

最简单的hello world 运行结束。但里面有一些问题。

运行报错

警告: An exceptionCaught() event was fired, and it reached at the tail of the pipeline. It usually means the last handler in the pipeline did not handle the exception.
java.io.IOException: Connection reset by peer
at java.base/sun.nio.ch.FileDispatcherImpl.read0(Native Method)
at java.base/sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:39)
at java.base/sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:276)
at java.base/sun.nio.ch.IOUtil.read(IOUtil.java:233)
at java.base/sun.nio.ch.IOUtil.read(IOUtil.java:223)
at java.base/sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:358)

修改一下 testHttpServerHandler

   @Override
    protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception{
        if (msg instanceof HttpRequest){
                    //... 代码省略
        }
    }

用谷歌浏览器会打印两次hello world

由于我们监听8899端口，并不关心uri，谷歌浏览器每次请求会额外请求一次图标favicon.ico,所以会打印两次hello world，testHttpServerHandler 可以改造如下

public class TestHttpServerHandler extends SimpleChannelInboundHandler<HttpObject> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception {

        if (msg instanceof HttpRequest) {
            HttpRequest httpRequest = (HttpRequest) msg;
            System.out.println(String.format("请求方法名：%s", httpRequest.method().name()));
            URI uri = new URI(httpRequest.uri());
            if ("/favicon.ico".equals(uri.getPath())) {
                System.out.println("请求favicon.ico");
                return;
            }
            ByteBuf content = Unpooled.copiedBuffer("hello world", CharsetUtil.UTF_8);
            DefaultHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, content);
            response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain");
            response.headers().set(HttpHeaderNames.CONTENT_LENGTH, content.readableBytes());
            ctx.writeAndFlush(response);
        }
    }
}

TestHttpServerHandler 中我们继承了SimpleChannelInboundHandler 。

public abstract class SimpleChannelInboundHandler<I> extends ChannelInboundHandlerAdapter {

SimpleChannelInboundHandler继承了ChannelInboundHandlerAdapter ，我们重写里面的方法看看调用顺序，在TestHttpServerHandler中加入这些方法。

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channelActive...");
        super.channelActive(ctx);
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channelInactive...");
        super.channelInactive(ctx);
    }


    @Override
    public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channelRegistered...");
        super.channelRegistered(ctx);
    }

    @Override
    public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channelUnregistered...");
        super.channelUnregistered(ctx);
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        System.out.println("handlerAdded...");
        super.handlerAdded(ctx);
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        System.out.println("handlerRemoved...");
        super.handlerRemoved(ctx);
    }

用 curl "http://localhost:8899" 调用，打印结果

handlerAdded...
channelRegistered...
channelActive...
channelInactive...
channelUnregistered...
handlerRemoved...

用浏览器调用

handlerAdded...
channelRegistered...
channelActive...

因为浏览器本身也是一个程序，我们用的是http1.1并不会马上关闭。

netty 概览与hello world(一)

netty概览

netty版本

hello world

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