http://www.open-open.com/lib/view/open1409642102932.html

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

  • @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() {// 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

  • @Title: HttpFileServerHandler.java

  • @Package NettyDemo.file.server Description: Version: 1.0

**************************/

public class FileServerHandler extends SimpleChannelInboundHandler {

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(“\r\n”);

buf.append(“”);

buf.append(“Listing of: “);

buf.append(dirPath);

buf.append(“\r\n”);

buf.append(“Listing of: “);

buf.append(dirPath);

buf.append("\r\n”);

buf.append(“”);

buf.append(“<a href="../">..\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(“<a href="");

buf.append(name);

buf.append("">”);

buf.append(name);

buf.append(“\r\n”);

}

buf.append(“\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