实现基于netty的web框架,了解一下

上一篇写了,基于netty实现的rpc的微框架,其中详细介绍netty的原理及组件,这篇就不过多介绍

这篇实现基于netty的web框架,你说netty强不强,文中有不对的地方,欢迎大牛指正

先普及几个知识点

@sharable

标注一个channel handler可以被多个channel安全地共享。
ChannelHandlerAdapter还提供了实用方法isSharable()。如果其对应的实现被标注为Sharable，那么这个方法将返回true，
表示它可以被添加到多个ChannelPipeline中。

因为一个ChannelHandler可以从属于多个ChannelPipeline，所以它也可以绑定到多个ChannelHandlerContext实例。
用于这种用法的ChannelHandler必须要使用@Sharable注解标注；否则，试图将它添加到多个ChannelPipeline时将会触发异常。
显而易见，为了安全地被用于多个并发的Channel（即连接），这样的ChannelHandler必须是线程安全的。

AtomicInteger:这个类的存在是为了满足在高并发的情况下,原生的整形数值自增线程不安全的问题,在Java语言中，++i和i++操作并不是线程安全的，在使用的时候，不可避免的会用到synchronized关键字。而AtomicInteger则通过一种线程安全的加减操作接口。AtomicInteger为什么能够达到多而不乱，处理高并发应付自如呢？

  这是由硬件提供原子操作指令实现的，这里面用到了一种并发技术：CAS。在非激烈竞争的情况下，开销更小，速度更快

TimeUnit: 

TimeUnit是Java.util.concurrent包下面的一个类。它提供了两大功能：

1）提供了可读性更好的线程暂停操作，通常用来替换Thread.sleep()； 

2）提供了便捷方法用于把时间转换成不同单位，如把秒转换成毫秒；

TimeUnit.MINUTES.sleep(4);  // sleeping for 4 minutes

Thread.sleep(4*60*1000);

项目的目录结构

上代码,分享一些关键的代码,后续的giuhub上的demo的注释很详细

//Netty 事件回调类
@Sharable
public class MessageCollector extends ChannelInboundHandlerAdapter {
    private final static Logger LOG = LoggerFactory.getLogger(MessageCollector.class);
    //业务线程池
    private ThreadPoolExecutor[] executors;
    private RequestDispatch requestDispatch;
    //业务队列最大值
    private int requestsMaxInflight=1000;

    public MessageCollector(int workerThreads,RequestDispatch dispatch){
        //给业务线程命名
        ThreadFactory factory =new ThreadFactory() {
            AtomicInteger seq=new AtomicInteger();
            @Override
            public Thread newThread(Runnable r) {
                Thread thread =new Thread(r);
                thread.setName("http-"+seq.getAndIncrement());
                return thread;
            }
        };
        this.executors=new ThreadPoolExecutor[workerThreads];
        for(int i=0;i<workerThreads;i++){
            ArrayBlockingQueue queue=new ArrayBlockingQueue<Runnable>(requestsMaxInflight);
            ////闲置时间超过30秒的线程就自动销毁
            this.executors[i]=new ThreadPoolExecutor(1,1,
                    30, TimeUnit.SECONDS, queue,factory,new CallerRunsPolicy());
        }

        this.requestDispatch=dispatch;
    }

    public  void  closeGracefully(){
        //优雅一点关闭,先通知,再等待,最后强制关闭
        for (int i=0;i<executors.length;i++){
            ThreadPoolExecutor executor=executors[i];
            try {
                executor.awaitTermination(10,TimeUnit.SECONDS);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            executor.shutdownNow();
        }
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        //客户端来了一个新的连接
       LOG.info("connection comes {}",ctx.channel().remoteAddress());
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        //客户端走了一个
        LOG.info("connection leaves {}",ctx.channel().remoteAddress());
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if (msg instanceof FullHttpRequest){
            FullHttpRequest req= (FullHttpRequest) msg;
            CRC32 crc32=new CRC32();
            crc32.update(ctx.hashCode());
            int idx =(int) (crc32.getValue()%executors.length);
            //用业务线程处理消息
            this.executors[idx].execute(() ->{
                requestDispatch.dispatch(ctx,req);
            });
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        //此处可能因为客户机器突发重启
        //也可能客户端连接时间超时,后面的REadTimeoutHandle抛出异常
        //也可能消息协议错误,序列化异常
        ctx.close();
    }
}

HttpServer

public class HttpServer {
    private final static Logger LOG= LoggerFactory.getLogger(HttpServer.class);
    private String ip;
    private int port;  //端口
    private int ioThreads;  //IO线程数,用于处理套接字读写,由Netty内部管理
    private int workerThreads;  //业务线程数,专门处理http请求,由我们本省框架管理
    private RequestDispatch requestDispatch;//请求配发器对象

    public HttpServer() {
    }

    public HttpServer(String ip, int port, int ioThreads,
                      int workerThreads, RequestDispatch requestDispatch) {
        this.ip = ip;
        this.port = port;
        this.ioThreads = ioThreads;
        this.workerThreads = workerThreads;
        this.requestDispatch = requestDispatch;
    }
    //用于服务端,使用一个ServerChannel接收客户端的连接,
    // 并创建对应的子Channel
    private ServerBootstrap bootstrap;
    //包含多个EventLoop
    private EventLoopGroup group;
    //代表一个Socket连接
    private Channel serverChannel;
    //
    private MessageCollector collector;

    public  void start(){
        bootstrap=new ServerBootstrap();
        group=new NioEventLoopGroup(ioThreads);
        bootstrap.group(group);
        collector=new MessageCollector(workerThreads,requestDispatch);
        bootstrap.channel(NioServerSocketChannel.class).childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel socketChannel) throws Exception {
                ChannelPipeline pipeline=socketChannel.pipeline();
                //如果客户端60秒没有任何请求,就关闭客户端连接
                pipeline.addLast(new ReadTimeoutHandler(10));
                //客户端和服务器简单的编解码器：HttpClientCodec和HttpServerCodec。
                //ChannelPipelien中有解码器和编码器(或编解码器)后就可以操作不同的HttpObject消息了；但是HTTP请求和响应可以有很多消息数据，
                // 你需要处理不同的部分，可能也需要聚合这些消息数据
                pipeline.addLast(new HttpServerCodec());
                //通过HttpObjectAggregator，Netty可以聚合HTTP消息，
                // 使用FullHttpResponse和FullHttpRequest到ChannelPipeline中的下一个ChannelHandler，这就消除了断裂消息，保证了消息的完整
                pipeline.addLast(new HttpObjectAggregator(1 << 30)); // max_size = 1g
                //允许通过处理ChunkedInput来写大的数据块
                pipeline.addLast(new ChunkedWriteHandler());
                //将业务处理器放到最后
                pipeline.addLast(collector);
            }
        });
    }

    public void stop() {
        // 先关闭服务端套件字
        serverChannel.close();
        // 再斩断消息来源，停止io线程池
        group.shutdownGracefully();
        // 最后停止业务线程
        collector.closeGracefully();
    }

}

RequestDispatcherImpl 是请求派发器，用于将收到的HTTP请求对象扔给响应的RequestHandler进行处理。

public class RequestDispatcherImpl implements RequestDispatch {
    private final static Logger LOG = LoggerFactory.getLogger(RequestDispatcherImpl.class);

    private String contextRoot;
    private Router router;
    private Map<Integer, WebExceptionHandler> exceptionHandlers = new HashMap<>();
    private WebExceptionHandler defaultExceptionHandler = new DefaultExceptionHandler();

    private WebTemplateEngine templateEngine = new WebTemplateEngine() {
    };

    static class DefaultExceptionHandler implements WebExceptionHandler {

        @Override
        public void handle(ApplicationContext ctx, AbortException e) {
            if (e.getStatus().code() == 500) {
                LOG.error("Internal Server Error", e);
            }
            ctx.error(e.getContent(), e.getStatus().code());
        }

    }

    public RequestDispatcherImpl(Router router) {
        this("/", router);
    }

    public RequestDispatcherImpl(String contextRoot, Router router) {
        this.contextRoot = CurrentUtil.normalize(contextRoot);
        this.router = router;
    }

    public RequestDispatcherImpl templateRoot(String templateRoot) {
        this.templateEngine = new FreemarkerEngine(templateRoot);
        return this;
    }

    public String root() {
        return contextRoot;
    }

    public RequestDispatcherImpl exception(int code, WebExceptionHandler handler) {
        this.exceptionHandlers.put(code, handler);
        return this;
    }

    public RequestDispatcherImpl exception(WebExceptionHandler handler) {
        this.defaultExceptionHandler = handler;
        return this;
    }
    @Override
    public void dispatch(ChannelHandlerContext channelCtx, FullHttpRequest req) {
        ApplicationContext ctx = new ApplicationContext(channelCtx, contextRoot, templateEngine);
        try {
            this.handleImpl(ctx, new Request(req));
        } catch (AbortException e) {
            this.handleException(ctx, e);
        } catch (Exception e) {
            this.handleException(ctx, new AbortException(HttpResponseStatus.INTERNAL_SERVER_ERROR, e));
        } finally {
            req.release();
        }
    }

    private void handleException(ApplicationContext ctx, AbortException e) {
        WebExceptionHandler handler = this.exceptionHandlers.getOrDefault(e.getStatus().code(), defaultExceptionHandler);
        try {
            handler.handle(ctx, e);
        } catch (Exception ex) {
            this.defaultExceptionHandler.handle(ctx, new AbortException(HttpResponseStatus.INTERNAL_SERVER_ERROR, ex));
        }
    }

    private void handleImpl(ApplicationContext ctx, Request req) throws Exception {
        if (req.decoderResult().isFailure()) {
            ctx.abort(400, "http protocol decode failed");
        }
        if (req.relativeUri().contains("./") || req.relativeUri().contains(".\\")) {
            ctx.abort(400, "unsecure url not allowed");
        }
        if (!req.relativeUri().startsWith(contextRoot)) {
            throw new AbortException(HttpResponseStatus.NOT_FOUND);
        }
        req.popRootUri(contextRoot);
        router.handle(ctx, req);
    }
}

项目github位置

https://github.com/developerxiaofeng/WebFrameByNetty.git