Netty HTTP 服务端入门开发

2022-10-28 09:56:28

一. HTTP 简介

　　HTTP(超文本传输协议) 协议是建立在 TCP 传输协议之上的应用层协议,它的发展是万维网协会和 Internet 工作小组和 IETF 合作的结果. HTTP 是一个属于应用层的面向对象的协议,由于其便捷,快速的方式,适用于分布式超媒体信息系统.

　　HTTP 协议的主要特点如下:

  1. 支持 Client/Server 模式.
  2. 简单---- 客户端向服务器请求服务时,只需指定服务的 URL, 携带必要的请求参数或者消息体;
  3. 灵活---- HTTP 允许传输任意类型的数据对象,传输内容类型有 HTTP 消息头中得 Content-Type 指定.
  4. 无状态---- HTTP 协议是无状态协议,无状态是指协议对于会话状态没有记忆功能,缺少状态意味着如果后续处理需要之前的信息,则它必须重传.这样导致每次连接传送的数据量加大另外一方面,在服务器不需要之前的信息时,它的应答就较快,负载较轻.

　　netty 的 Http 协议栈是基于 Netty 的 Nio 通信框架开发的.因此, Netty 的 Http 协议也是异步非阻塞的.

代码如下:

HttpFileServer

package netty.protocol.http;

import io.netty.bootstrap.ServerBootstrap;

import io.netty.channel.ChannelFuture;

import io.netty.channel.ChannelInitializer;

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.HttpObjectAggregator;

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

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

import io.netty.handler.stream.ChunkedWriteHandler;

/**

 * TODO

 *

 * @description

 * @author ez

 * @time 2015年6月3日 上午10:47:37

 */

public class HttpFileServer {

    private static final String DEFAULT_URL = "/src/main/java/netty/protocol/http/";

    public void run(final int port, final String url) 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<SocketChannel>() {

                        @Override

                        protected void initChannel(SocketChannel ch)

                                throws Exception {

                            ch.pipeline().addLast("http-decoder",

                                    new HttpRequestDecoder()); // http 请求消息解码器,

                            /*

                             * httpObject 解码器,

                             * 它的作用是将多个消息转换为单一的FullHttpRequest或FullHttpResponse

                             * 对象,原因是HTTP 解码器在每个HTTP消息中会生成多个消息对象 (

                             * HttpRequest/HttpResponse

                             * ,HttpContent,LastHttpContent)

                             */

                            ch.pipeline().addLast("http-aggregator",

                                    new HttpObjectAggregator(65536));

                            /*

                             * HTTP 响应消息编码器

                             */

                            ch.pipeline().addLast("http-encoder",

                                    new HttpResponseEncoder());

                            /*

                             * ChunkedWriteHandler

                             * 的主要作用是支持异步发送大的码流(例如大文件传输),但不占用过多的内存,防止JAVA内存溢出

                             */

                            ch.pipeline().addLast("http-chunked",

                                    new ChunkedWriteHandler());

                            /*

                             * 业务处理类

                             */

                            ch.pipeline().addLast("fileServerHandler",

                                    new HttpFileServerHandler(url));

                        }

                    });

            ChannelFuture future = b.bind("localhost", port).sync();

            System.out.println("HTTP文件目录服务器启动，网址是 : " + "http://localhost:"

                    + port + url);

            future.channel().closeFuture().sync();

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            bossGroup.shutdownGracefully();

            workerGroup.shutdownGracefully();

        }

    }

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

        int port = 8080;

        if (args.length > 0) {

            try {

                port = Integer.parseInt(args[0]);

            } catch (NumberFormatException e) {

                e.printStackTrace();

            }

        }

        String url = DEFAULT_URL;

        if (args.length > 1)

            url = args[1];

        new HttpFileServer().run(port, url);

    }

}

ServerHandler

package netty.protocol.http;

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

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

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

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

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

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

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

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

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

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

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

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

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.ChannelFuture;

import io.netty.channel.ChannelFutureListener;

import io.netty.channel.ChannelHandlerContext;

import io.netty.channel.ChannelProgressiveFuture;

import io.netty.channel.ChannelProgressiveFutureListener;

import io.netty.channel.SimpleChannelInboundHandler;

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

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

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

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

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

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

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

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

import io.netty.handler.stream.ChunkedFile;

import io.netty.util.CharsetUtil;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.RandomAccessFile;

import java.io.UnsupportedEncodingException;

import java.net.URLDecoder;

import java.util.regex.Pattern;

import javax.activation.MimetypesFileTypeMap;

public class HttpFileServerHandler extends

        SimpleChannelInboundHandler<FullHttpRequest> {

    private final String url;

    public HttpFileServerHandler(String url) {

        this.url = url;

    }

    @Override

    public void messageReceived(ChannelHandlerContext ctx,

            FullHttpRequest request) throws Exception {

        /*

         * 首先对HTTP请求消息的解码结构进行判断,如果解码失败,直接构造HTTP404 错误返回,

         */

        if (!request.getDecoderResult().isSuccess()) {

            sendError(ctx, BAD_REQUEST);

            return;

        }

        /*

         * 如果不是get请求, 则构造 HTTP405 返回

         */

        if (request.getMethod() != GET) {

            sendError(ctx, METHOD_NOT_ALLOWED);

            return;

        }

        final String uri = request.getUri();

        /*

         * 对URL进行解码, 使用 UTF-8字符集,解码之后对URI进行合法性判断,

         */

        final String path = sanitizeUri(uri);

        if (path == null) {

            sendError(ctx, FORBIDDEN);

            return;

        }

        File file = new File(path);

        if (file.isHidden() || !file.exists()) {

            sendError(ctx, NOT_FOUND);

            return;

        }

        if (file.isDirectory()) {

            if (uri.endsWith("/")) {

                sendListing(ctx, file);

            } else {

                sendRedirect(ctx, uri + '/');

            }

            return;

        }

        if (!file.isFile()) {

            sendError(ctx, FORBIDDEN);

            return;

        }

        RandomAccessFile randomAccessFile = null;

        try {

            randomAccessFile = new RandomAccessFile(file, "r");// 以只读的方式打开文件

        } catch (FileNotFoundException fnfe) {

            sendError(ctx, NOT_FOUND);

            return;

        }

        long fileLength = randomAccessFile.length();

        HttpResponse response = new DefaultHttpResponse(HTTP_1_1, OK);

        setContentLength(response, fileLength);

        setContentTypeHeader(response, file);

        if (isKeepAlive(request)) {

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

        }

        ctx.write(response);

        ChannelFuture sendFileFuture;

        sendFileFuture = ctx.write(new ChunkedFile(randomAccessFile, 0,

                fileLength, 8192), ctx.newProgressivePromise());

        sendFileFuture.addListener(new ChannelProgressiveFutureListener() {

            public void operationProgressed(ChannelProgressiveFuture future,

                    long progress, long total) {

                if (total < 0) { // total unknown

                    System.err.println("Transfer progress: " + progress);

                } else {

                    System.err.println("Transfer progress: " + progress + " / "

                            + total);

                }

            }

            public void operationComplete(ChannelProgressiveFuture future)

                    throws Exception {

                System.out.println("Transfer complete.");

            }

        });

        /*

         * 如果是chunked 编码, 最后需要发送一个编码结束的空消息体,将LastHttpContent的EMPTY_LAST_CONTENT

         * 发送到缓存区中,标识所有的消息体已经发送完成,同时调用flush方法将之前在发送缓冲区的消息刷新到SocketChannel中发送给对方

         */

        ChannelFuture lastContentFuture = ctx

                .writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);

        /*

         * 如果是非 Keep-Alive 的,最后一包消息发送完之后,服务端要主动关闭连接.

         */

        if (!isKeepAlive(request)) {

            lastContentFuture.addListener(ChannelFutureListener.CLOSE);

        }

    }

    @Override

    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)

            throws Exception {

        cause.printStackTrace();

        if (ctx.channel().isActive()) {

            sendError(ctx, INTERNAL_SERVER_ERROR);

        }

    }

    private static final Pattern INSECURE_URI = Pattern.compile(".*[<>&\"].*");

    private String sanitizeUri(String uri) {

        try {

            uri = URLDecoder.decode(uri, "UTF-8");

        } catch (UnsupportedEncodingException e) {

            try {

                uri = URLDecoder.decode(uri, "ISO-8859-1");

            } catch (UnsupportedEncodingException e1) {

                throw new Error();

            }

        }

        if (!uri.startsWith(url)) {

            return null;

        }

        if (!uri.startsWith("/")) {

            return null;

        }

        uri = uri.replace('/', File.separatorChar);

        if (uri.contains(File.separator + '.')

                || uri.contains('.' + File.separator) || uri.startsWith(".")

                || uri.endsWith(".") || INSECURE_URI.matcher(uri).matches()) {

            return null;

        }

        return System.getProperty("user.dir") + File.separator + uri;

    }

    private static final Pattern ALLOWED_FILE_NAME = Pattern

            .compile("[A-Za-z0-9][-_A-Za-z0-9\\.]*");

    private static void sendListing(ChannelHandlerContext ctx, File dir) {

        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK);

        response.headers().set(CONTENT_TYPE, "text/html; charset=UTF-8");

        StringBuilder buf = new StringBuilder();

        String dirPath = dir.getPath();

        buf.append("<!DOCTYPE html>\r\n");

        buf.append("<html><head><title>");

        buf.append(dirPath);

        buf.append(" 目录：");

        buf.append("</title></head><body>\r\n");

        buf.append("<h3>");

        buf.append(dirPath).append(" 目录：");

        buf.append("</h3>\r\n");

        buf.append("<ul>");

        buf.append("<li>链接：<a href=\"../\">..</a></li>\r\n");

        for (File f : dir.listFiles()) {

            if (f.isHidden() || !f.canRead()) {

                continue;

            }

            String name = f.getName();

            if (!ALLOWED_FILE_NAME.matcher(name).matches()) {

                continue;

            }

            buf.append("<li>链接：<a href=\"");

            buf.append(name);

            buf.append("\">");

            buf.append(name);

            buf.append("</a></li>\r\n");

        }

        buf.append("</ul></body></html>\r\n");

        ByteBuf buffer = Unpooled.copiedBuffer(buf, CharsetUtil.UTF_8);

        response.content().writeBytes(buffer);

        buffer.release();

        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);

    }

    private static void sendRedirect(ChannelHandlerContext ctx, String newUri) {

        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, FOUND);

        response.headers().set(LOCATION, newUri);

        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);

    }

    private static void sendError(ChannelHandlerContext ctx,

            HttpResponseStatus status) {

        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1,

                status, Unpooled.copiedBuffer("Failure: " + status.toString()

                        + "\r\n", CharsetUtil.UTF_8));

        response.headers().set(CONTENT_TYPE, "text/plain; charset=UTF-8");

        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);

    }

    private static void setContentTypeHeader(HttpResponse response, File file) {

        MimetypesFileTypeMap mimeTypesMap = new MimetypesFileTypeMap();

        response.headers().set(CONTENT_TYPE,

                mimeTypesMap.getContentType(file.getPath()));

    }

}

以上内容出自 <netty 权威指南>

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