实例：如何使用 Netty 下载文件
浏览数：344 /
时间：2015年06月09日
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:[email protected]>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(); } } }
</pre><pre>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:[email protected]>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())); } }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
ps:通过对本例进行简单修改可实现各种方式的文件下载
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