使用 Netty 下载文件实例

jopen 7年前

本实例主要参考的是官网的examples:点击这里

使用场景:客户端向Netty请求一个文件,Netty服务端下载指定位置文件到客户端。

本实例使用的是Http协议,当然,可以通过简单的修改即可换成TCP协议。

需要注意本实例的关键点是,为了更高效的传输大数据,实例中用到了ChunkedWriteHandler编码器,它提供了以zero-memory-copy方式写文件。

第一步:先写一个HttpFileServer

    package NettyDemo.file.server;                import io.netty.bootstrap.ServerBootstrap;        import io.netty.channel.Channel;        import io.netty.channel.ChannelInitializer;        import io.netty.channel.ChannelPipeline;        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.HttpServerCodec;        import io.netty.handler.logging.LogLevel;        import io.netty.handler.logging.LoggingHandler;        import io.netty.handler.stream.ChunkedWriteHandler;                /*******************************************************************************        * Reserved. BidPlanStructForm.java Created on 2014-8-19 Author: <a        * href=mailto:wanghouda@126.com>wanghouda</a>        * @Title: HttpFileServer.java        * @Package NettyDemo.file.server Description: Version: 1.0        ******************************************************************************/        public class HttpFileServer {            static final int PORT = 8080;            public static void main(String[] args) throws Exception {                EventLoopGroup bossGroup = new NioEventLoopGroup(1);                EventLoopGroup workerGroup = new NioEventLoopGroup();                try {                    ServerBootstrap b = new ServerBootstrap();                    b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).handler(new LoggingHandler(LogLevel.INFO))                            .childHandler(new ChannelInitializer<SocketChannel>() {// 有连接到达时会创建一个channel                                        @Override                                        protected void initChannel(SocketChannel ch) throws Exception {                                            ChannelPipeline pipeline = ch.pipeline();                                            pipeline.addLast(new HttpServerCodec());                                            pipeline.addLast(new HttpObjectAggregator(65536));                                            pipeline.addLast(new ChunkedWriteHandler());                                            pipeline.addLast(new FileServerHandler());                                        }                                    });                            Channel ch = b.bind(PORT).sync().channel();                    System.err.println("打开浏览器,输入: " + ("http") + "://127.0.0.1:" + PORT + '/');                    ch.closeFuture().sync();                } finally {                    bossGroup.shutdownGracefully();                    workerGroup.shutdownGracefully();                }            }        }  

 
第二步:再写一个FileServerHandler
    package NettyDemo.file.server;                import static io.netty.handler.codec.http.HttpHeaders.Names.CACHE_CONTROL;        import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_TYPE;        import static io.netty.handler.codec.http.HttpHeaders.Names.DATE;        import static io.netty.handler.codec.http.HttpHeaders.Names.EXPIRES;        import static io.netty.handler.codec.http.HttpHeaders.Names.IF_MODIFIED_SINCE;        import static io.netty.handler.codec.http.HttpHeaders.Names.LAST_MODIFIED;        import static io.netty.handler.codec.http.HttpHeaders.Names.LOCATION;        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.NOT_FOUND;        import static io.netty.handler.codec.http.HttpResponseStatus.NOT_MODIFIED;        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.DefaultFileRegion;        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.HttpChunkedInput;        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.HttpVersion;        import io.netty.handler.codec.http.LastHttpContent;        import io.netty.handler.ssl.SslHandler;        import io.netty.handler.stream.ChunkedFile;        import io.netty.util.CharsetUtil;        import io.netty.util.internal.SystemPropertyUtil;                import java.io.File;        import java.io.FileNotFoundException;        import java.io.RandomAccessFile;        import java.io.UnsupportedEncodingException;        import java.net.URLDecoder;        import java.text.SimpleDateFormat;        import java.util.Calendar;        import java.util.Date;        import java.util.GregorianCalendar;        import java.util.Locale;        import java.util.TimeZone;        import java.util.regex.Pattern;                import javax.activation.MimetypesFileTypeMap;                /*******************************************************************************        * Created on 2014-8-19 Author:        * <href=mailto:wanghouda@126.com>wanghouda</a>        *         * @Title: HttpFileServerHandler.java        * @Package NettyDemo.file.server Description: Version: 1.0        ******************************************************************************/        public class FileServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {            public static final String HTTP_DATE_FORMAT = "EEE, dd MMM yyyy HH:mm:ss zzz";            public static final String HTTP_DATE_GMT_TIMEZONE = "GMT";            public static final int HTTP_CACHE_SECONDS = 60;                    @Override            protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {                // 监测解码情况                if (!request.getDecoderResult().isSuccess()) {                    sendError(ctx, BAD_REQUEST);                    return;                }                final String uri = request.getUri();                final String path = sanitizeUri(uri);                if (path == null) {                    sendError(ctx, FORBIDDEN);                    return;                }                //读取要下载的文件                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;                }                // Cache Validation                String ifModifiedSince = request.headers().get(IF_MODIFIED_SINCE);                if (ifModifiedSince != null && !ifModifiedSince.isEmpty()) {                    SimpleDateFormat dateFormatter = new SimpleDateFormat(HTTP_DATE_FORMAT, Locale.US);                    Date ifModifiedSinceDate = dateFormatter.parse(ifModifiedSince);                    // Only compare up to the second because the datetime format we send                    // to the client                    // does not have milliseconds                    long ifModifiedSinceDateSeconds = ifModifiedSinceDate.getTime() / 1000;                    long fileLastModifiedSeconds = file.lastModified() / 1000;                    if (ifModifiedSinceDateSeconds == fileLastModifiedSeconds) {                        sendNotModified(ctx);                        return;                    }                }                RandomAccessFile raf;                try {                    raf = new RandomAccessFile(file, "r");                } catch (FileNotFoundException ignore) {                    sendError(ctx, NOT_FOUND);                    return;                }                long fileLength = raf.length();                HttpResponse response = new DefaultHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);                HttpHeaders.setContentLength(response, fileLength);                setContentTypeHeader(response, file);                setDateAndCacheHeaders(response, file);                if (HttpHeaders.isKeepAlive(request)) {                    response.headers().set("CONNECTION", HttpHeaders.Values.KEEP_ALIVE);                }                        // Write the initial line and the header.                ctx.write(response);                        // Write the content.                ChannelFuture sendFileFuture;                if (ctx.pipeline().get(SslHandler.class) == null) {                    sendFileFuture = ctx.write(new DefaultFileRegion(raf.getChannel(), 0, fileLength), ctx.newProgressivePromise());                } else {                    sendFileFuture = ctx.write(new HttpChunkedInput(new ChunkedFile(raf, 0, fileLength, 8192)), ctx.newProgressivePromise());                }                sendFileFuture.addListener(new ChannelProgressiveFutureListener() {                    @Override                    public void operationProgressed(ChannelProgressiveFuture future, long progress, long total) {                        if (total < 0) { // total unknown                            System.err.println(future.channel() + " Transfer progress: " + progress);                        } else {                            System.err.println(future.channel() + " Transfer progress: " + progress + " / " + total);                        }                    }                            @Override                    public void operationComplete(ChannelProgressiveFuture future) {                        System.err.println(future.channel() + " Transfer complete.");                    }                });                        // Write the end marker                ChannelFuture lastContentFuture = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);                        // Decide whether to close the connection or not.                if (!HttpHeaders.isKeepAlive(request)) {                    // Close the connection when the whole content is written out.                    lastContentFuture.addListener(ChannelFutureListener.CLOSE);                }            }                    @Override            public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {                cause.printStackTrace();                if (ctx.channel().isActive()) {                    sendError(ctx, INTERNAL_SERVER_ERROR);                }            }                    private static final Pattern INSECURE_URI = Pattern.compile(".*[<>&\"].*");                    private static String sanitizeUri(String uri) {                // Decode the path.                try {                    uri = URLDecoder.decode(uri, "UTF-8");                } catch (UnsupportedEncodingException e) {                    throw new Error(e);                }                        if (!uri.startsWith("/")) {                    return null;                }                        // Convert file separators.                uri = uri.replace('/', File.separatorChar);                        // Simplistic dumb security check.                // You will have to do something serious in the production environment.                if (uri.contains(File.separator + '.') || uri.contains('.' + File.separator) || uri.startsWith(".") || uri.endsWith(".")                        || INSECURE_URI.matcher(uri).matches()) {                    return null;                }                        // Convert to absolute path.                return SystemPropertyUtil.get("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("Listing of: ");                buf.append(dirPath);                buf.append("</title></head><body>\r\n");                        buf.append("<h3>Listing of: ");                buf.append(dirPath);                buf.append("</h3>\r\n");                        buf.append("<ul>");                buf.append("<li><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><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();                        // Close the connection as soon as the error message is sent.                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);                        // Close the connection as soon as the error message is sent.                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 + "\r\n", CharsetUtil.UTF_8));                response.headers().set(CONTENT_TYPE, "text/plain; charset=UTF-8");                        // Close the connection as soon as the error message is sent.                ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);            }                    /**            * When file timestamp is the same as what the browser is sending up, send a            * "304 Not Modified"            *             * @param ctx            *            Context            */            private static void sendNotModified(ChannelHandlerContext ctx) {                FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, NOT_MODIFIED);                setDateHeader(response);                        // Close the connection as soon as the error message is sent.                ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);            }                    /**            * Sets the Date header for the HTTP response            *             * @param response            *            HTTP response            */            private static void setDateHeader(FullHttpResponse response) {                SimpleDateFormat dateFormatter = new SimpleDateFormat(HTTP_DATE_FORMAT, Locale.US);                dateFormatter.setTimeZone(TimeZone.getTimeZone(HTTP_DATE_GMT_TIMEZONE));                        Calendar time = new GregorianCalendar();                response.headers().set(DATE, dateFormatter.format(time.getTime()));            }                    /**            * Sets the Date and Cache headers for the HTTP Response            *             * @param response            *            HTTP response            * @param fileToCache            *            file to extract content type            */            private static void setDateAndCacheHeaders(HttpResponse response, File fileToCache) {                SimpleDateFormat dateFormatter = new SimpleDateFormat(HTTP_DATE_FORMAT, Locale.US);                dateFormatter.setTimeZone(TimeZone.getTimeZone(HTTP_DATE_GMT_TIMEZONE));                        // Date header                Calendar time = new GregorianCalendar();                response.headers().set(DATE, dateFormatter.format(time.getTime()));                        // Add cache headers                time.add(Calendar.SECOND, HTTP_CACHE_SECONDS);                response.headers().set(EXPIRES, dateFormatter.format(time.getTime()));                response.headers().set(CACHE_CONTROL, "private, max-age=" + HTTP_CACHE_SECONDS);                response.headers().set(LAST_MODIFIED, dateFormatter.format(new Date(fileToCache.lastModified())));            }                    /**            * Sets the content type header for the HTTP Response            *             * @param response            *            HTTP response            * @param file            *            file to extract content type            */            private static void setContentTypeHeader(HttpResponse response, File file) {                MimetypesFileTypeMap mimeTypesMap = new MimetypesFileTypeMap();                response.headers().set(CONTENT_TYPE, mimeTypesMap.getContentType(file.getPath()));            }                }  
</div> </div> 第三步:启动Netty服务,在浏览器中输入
     http://127.0.0.1:8080/

     如图所示:即可在浏览器中看到工程目录下所有文件,点击即可下载
20140819114843221.png

 来自:http://blog.csdn.net/suifeng3051/article/details/38679507