厲害了，Netty 輕松實現文件上傳！

本文轉載自查看原文 2021-07-06 13:34 196

作者：rickiyang

出處：www.cnblogs.com/rickiyang/p/11074222.html

今天我們來完成一個使用netty進行文件傳輸的任務。在實際項目中，文件傳輸通常采用FTP或者HTTP附件的方式。事實上通過TCP Socket+File的方式進行文件傳輸也有一定的應用場景，盡管不是主流，但是掌握這種文件傳輸方式還是比較重要的，特別是針對兩個跨主機的JVM進程之間進行持久化數據的相互交換。

而使用netty來進行文件傳輸也是利用netty天然的優勢：零拷貝功能。很多同學都聽說過netty的”零拷貝”功能，但是具體體現在哪里又不知道，下面我們就簡要介紹下：

Netty的“零拷貝”主要體現在如下三個方面：

Netty的接收和發送ByteBuffer采用DIRECT BUFFERS，使用堆外直接內存進行Socket讀寫，不需要進行字節緩沖區的二次拷貝。如果使用傳統的堆內存（HEAP BUFFERS）進行Socket讀寫，JVM會將堆內存Buffer拷貝一份到直接內存中，然后才寫入Socket中。相比於堆外直接內存，消息在發送過程中多了一次緩沖區的內存拷貝。
Netty提供了組合Buffer對象，可以聚合多個ByteBuffer對象，用戶可以像操作一個Buffer那樣方便的對組合Buffer進行操作，避免了傳統通過內存拷貝的方式將幾個小Buffer合並成一個大的Buffer。
Netty的文件傳輸采用了transferTo方法，它可以直接將文件緩沖區的數據發送到目標Channel，避免了傳統通過循環write方式導致的內存拷貝問題。

具體的分析在此就不多做介紹，有興趣的可以查閱相關文檔。我們還是把重點放在文件傳輸上。Netty作為高性能的服務器端異步IO框架必然也離不開文件讀寫功能，我們可以使用netty模擬http的形式通過網頁上傳文件寫入服務器，當然要使用http的形式那你也用不着netty！大材小用。

netty4中如果想使用http形式上傳文件你還得借助第三方jar包：okhttp。使用該jar完成http請求的發送。但是在netty5 中已經為我們寫好了，我們可以直接調用netty5的API就可以實現。所以netty4和5的差別還是挺大的，至於使用哪個，那就看你們公司選擇哪一個了！本文目前使用netty4來實現文件上傳功能。下面我們上代碼：

pom文件：

<dependency>
      <groupId>io.netty</groupId>
        <artifactId>netty-all</artifactId>
      <version>4.1.5.Final</version>
</dependency>

server端：

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.serialization.ClassResolvers;
import io.netty.handler.codec.serialization.ObjectDecoder;
import io.netty.handler.codec.serialization.ObjectEncoder;

public class FileUploadServer {
    public void bind(int port) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 1024).childHandler(new ChannelInitializer<Channel>() {

                @Override
                protected void initChannel(Channel ch) throws Exception {
                    ch.pipeline().addLast(new ObjectEncoder());
                    ch.pipeline().addLast(new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.weakCachingConcurrentResolver(null))); // 最大長度
                    ch.pipeline().addLast(new FileUploadServerHandler());
                }
            });
            ChannelFuture f = b.bind(port).sync();
            f.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                e.printStackTrace();
            }
        }
        try {
            new FileUploadServer().bind(port);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

server端handler：

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.io.File;
import java.io.RandomAccessFile;

public class FileUploadServerHandler extends ChannelInboundHandlerAdapter {
    private int byteRead;
    private volatile int start = 0;
    private String file_dir = "D:";

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if (msg instanceof FileUploadFile) {
            FileUploadFile ef = (FileUploadFile) msg;
            byte[] bytes = ef.getBytes();
            byteRead = ef.getEndPos();
            String md5 = ef.getFile_md5();//文件名
            String path = file_dir + File.separator + md5;
            File file = new File(path);
            RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
            randomAccessFile.seek(start);
            randomAccessFile.write(bytes);
            start = start + byteRead;
            if (byteRead > 0) {
                ctx.writeAndFlush(start);
            } else {
                randomAccessFile.close();
                ctx.close();
            }
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

client端：

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.serialization.ClassResolvers;
import io.netty.handler.codec.serialization.ObjectDecoder;
import io.netty.handler.codec.serialization.ObjectEncoder;
import java.io.File;

public class FileUploadClient {
    public void connect(int port, String host, final FileUploadFile fileUploadFile) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioSocketChannel.class).option(ChannelOption.TCP_NODELAY, true).handler(new ChannelInitializer<Channel>() {

                @Override
                protected void initChannel(Channel ch) throws Exception {
                    ch.pipeline().addLast(new ObjectEncoder());
                    ch.pipeline().addLast(new ObjectDecoder(ClassResolvers.weakCachingConcurrentResolver(null)));
                    ch.pipeline().addLast(new FileUploadClientHandler(fileUploadFile));
                }
            });
            ChannelFuture f = b.connect(host, port).sync();
            f.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                e.printStackTrace();
            }
        }
        try {
            FileUploadFile uploadFile = new FileUploadFile();
            File file = new File("c:/1.txt");
            String fileMd5 = file.getName();// 文件名
            uploadFile.setFile(file);
            uploadFile.setFile_md5(fileMd5);
            uploadFile.setStarPos(0);// 文件開始位置
            new FileUploadClient().connect(port, "127.0.0.1", uploadFile);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

client端handler：

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

public class FileUploadClientHandler extends ChannelInboundHandlerAdapter {
    private int byteRead;
    private volatile int start = 0;
    private volatile int lastLength = 0;
    public RandomAccessFile randomAccessFile;
    private FileUploadFile fileUploadFile;

    public FileUploadClientHandler(FileUploadFile ef) {
        if (ef.getFile().exists()) {
            if (!ef.getFile().isFile()) {
                System.out.println("Not a file :" + ef.getFile());
                return;
            }
        }
        this.fileUploadFile = ef;
    }

    public void channelActive(ChannelHandlerContext ctx) {
        try {
            randomAccessFile = new RandomAccessFile(fileUploadFile.getFile(), "r");
            randomAccessFile.seek(fileUploadFile.getStarPos());
            lastLength = (int) randomAccessFile.length() / 10;
            byte[] bytes = new byte[lastLength];
            if ((byteRead = randomAccessFile.read(bytes)) != -1) {
                fileUploadFile.setEndPos(byteRead);
                fileUploadFile.setBytes(bytes);
                ctx.writeAndFlush(fileUploadFile);
            } else {
                System.out.println("文件已經讀完");
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException i) {
            i.printStackTrace();
        }
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if (msg instanceof Integer) {
            start = (Integer) msg;
            if (start != -1) {
                randomAccessFile = new RandomAccessFile(fileUploadFile.getFile(), "r");
                randomAccessFile.seek(start);
                System.out.println("塊兒長度：" + (randomAccessFile.length() / 10));
                System.out.println("長度：" + (randomAccessFile.length() - start));
                int a = (int) (randomAccessFile.length() - start);
                int b = (int) (randomAccessFile.length() / 10);
                if (a < b) {
                    lastLength = a;
                }
                byte[] bytes = new byte[lastLength];
                System.out.println("-----------------------------" + bytes.length);
                if ((byteRead = randomAccessFile.read(bytes)) != -1 && (randomAccessFile.length() - start) > 0) {
                    System.out.println("byte 長度：" + bytes.length);
                    fileUploadFile.setEndPos(byteRead);
                    fileUploadFile.setBytes(bytes);
                    try {
                        ctx.writeAndFlush(fileUploadFile);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                } else {
                    randomAccessFile.close();
                    ctx.close();
                    System.out.println("文件已經讀完--------" + byteRead);
                }
            }
        }
    }

    // @Override
    // public void channelRead(ChannelHandlerContext ctx, Object msg) throws
    // Exception {
    // System.out.println("Server is speek ："+msg.toString());
    // FileRegion filer = (FileRegion) msg;
    // String path = "E://Apk//APKMD5.txt";
    // File fl = new File(path);
    // fl.createNewFile();
    // RandomAccessFile rdafile = new RandomAccessFile(path, "rw");
    // FileRegion f = new DefaultFileRegion(rdafile.getChannel(), 0,
    // rdafile.length());
    //
    // System.out.println("This is" + ++counter + "times receive server:["
    // + msg + "]");
    // }

    // @Override
    // public void channelReadComplete(ChannelHandlerContext ctx) throws
    // Exception {
    // ctx.flush();
    // }

    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
    // @Override
    // protected void channelRead0(ChannelHandlerContext ctx, String msg)
    // throws Exception {
    // String a = msg;
    // System.out.println("This is"+
    // ++counter+"times receive server:["+msg+"]");
    // }
}

我們還自定義了一個對象，用於統計文件上傳進度的：

import java.io.File;
import java.io.Serializable;

public class FileUploadFile implements Serializable {


    private static final long serialVersionUID = 1L;
    private File file;// 文件
    private String file_md5;// 文件名
    private int starPos;// 開始位置
    private byte[] bytes;// 文件字節數組
    private int endPos;// 結尾位置

    public int getStarPos() {
        return starPos;
    }

    public void setStarPos(int starPos) {
        this.starPos = starPos;
    }

    public int getEndPos() {
        return endPos;
    }

    public void setEndPos(int endPos) {
        this.endPos = endPos;
    }

    public byte[] getBytes() {
        return bytes;
    }

    public void setBytes(byte[] bytes) {
        this.bytes = bytes;
    }

    public File getFile() {
        return file;
    }

    public void setFile(File file) {
        this.file = file;
    }

    public String getFile_md5() {
        return file_md5;
    }

    public void setFile_md5(String file_md5) {
        this.file_md5 = file_md5;
    }
}

輸出為：

塊兒長度：894
長度：8052
-----------------------------894
byte 長度：894
塊兒長度：894
長度：7158
-----------------------------894
byte 長度：894
塊兒長度：894
長度：6264
-----------------------------894
byte 長度：894
塊兒長度：894
長度：5370
-----------------------------894
byte 長度：894
塊兒長度：894
長度：4476
-----------------------------894
byte 長度：894
塊兒長度：894
長度：3582
-----------------------------894
byte 長度：894
塊兒長度：894
長度：2688
-----------------------------894
byte 長度：894
塊兒長度：894
長度：1794
-----------------------------894
byte 長度：894
塊兒長度：894
長度：900
-----------------------------894
byte 長度：894
塊兒長度：894
長度：6
-----------------------------6
byte 長度：6
塊兒長度：894
長度：0
-----------------------------0
文件已經讀完--------0

Process finished with exit code 0

這樣就實現了服務器端文件的上傳，當然我們也可以使用http的形式。

server端：

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;


public class HttpFileServer implements Runnable {
    private int port;

    public HttpFileServer(int port) {
        super();
        this.port = port;
    }

    @Override
    public void run() {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        ServerBootstrap serverBootstrap = new ServerBootstrap();
        serverBootstrap.group(bossGroup, workerGroup);
        serverBootstrap.channel(NioServerSocketChannel.class);
        //serverBootstrap.handler(new LoggingHandler(LogLevel.INFO));
        serverBootstrap.childHandler(new HttpChannelInitlalizer());
        try {
            ChannelFuture f = serverBootstrap.bind(port).sync();
            f.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) {
        HttpFileServer b = new HttpFileServer(9003);
        new Thread(b).start();
    }
}

Server端initializer：

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.stream.ChunkedWriteHandler;


public class HttpChannelInitlalizer extends ChannelInitializer<SocketChannel> {

    @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 HttpChannelHandler());
    }

}

server端hadler：

import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_TYPE;
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.INTERNAL_SERVER_ERROR;
import static io.netty.handler.codec.http.HttpResponseStatus.NOT_FOUND;
import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
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.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.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.util.regex.Pattern;

import javax.activation.MimetypesFileTypeMap;

public class HttpChannelHandler 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 {
        // 監測解碼情況
        if (!request.getDecoderResult().isSuccess()) {
            sendError(ctx, BAD_REQUEST);
            return;
        }
        final String uri = request.getUri();
        final String path = sanitizeUri(uri);
        System.out.println("get file："+path);
        if (path == null) {
            sendError(ctx, FORBIDDEN);
            return;
        }
        //讀取要下載的文件
        File file = new File(path);
        if (file.isHidden() || !file.exists()) {
            sendError(ctx, NOT_FOUND);
            return;
        }
        if (!file.isFile()) {
            sendError(ctx, FORBIDDEN);
            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 =
        ctx.write(new HttpChunkedInput(new ChunkedFile(raf, 0, fileLength, 8192)), ctx.newProgressivePromise());
        //sendFuture用於監視發送數據的狀態
        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);
        }
        ctx.close();
    }

    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 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);
    }

    /**
     * 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 m = new MimetypesFileTypeMap();
        String contentType = m.getContentType(file.getPath());
        if (!contentType.equals("application/octet-stream")) {
            contentType += "; charset=utf-8";
        }
        response.headers().set(CONTENT_TYPE, contentType);
    }

}

client端：

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.http.DefaultFullHttpRequest;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpMethod;
import io.netty.handler.codec.http.HttpRequestEncoder;
import io.netty.handler.codec.http.HttpResponseDecoder;
import io.netty.handler.codec.http.HttpVersion;
import io.netty.handler.stream.ChunkedWriteHandler;

import java.net.URI;


public class HttpDownloadClient {
    /**
     * 下載http資源 向服務器下載直接填寫要下載的文件的相對路徑
     *        （↑↑↑建議只使用字母和數字對特殊字符對字符進行部分過濾可能導致異常↑↑↑）
     *        向互聯網下載輸入完整路徑
     * @param host 目的主機ip或域名
     * @param port 目標主機端口
     * @param url 文件路徑
     * @param local 本地存儲路徑
     * @throws Exception
     */
    public void connect(String host, int port, String url, final String local) throws Exception {
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(workerGroup);
            b.channel(NioSocketChannel.class);
            b.option(ChannelOption.SO_KEEPALIVE, true);
            b.handler(new ChildChannelHandler(local));

            // Start the client.
            ChannelFuture f = b.connect(host, port).sync();

            URI uri = new URI(url);
            DefaultFullHttpRequest request = new DefaultFullHttpRequest(
                    HttpVersion.HTTP_1_1, HttpMethod.GET, uri.toASCIIString());

            // 構建http請求
            request.headers().set(HttpHeaders.Names.HOST, host);
            request.headers().set(HttpHeaders.Names.CONNECTION,
                    HttpHeaders.Values.KEEP_ALIVE);
            request.headers().set(HttpHeaders.Names.CONTENT_LENGTH,
                    request.content().readableBytes());
            // 發送http請求
            f.channel().write(request);
            f.channel().flush();
            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
        }

    }

    private class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
        String local;
        public ChildChannelHandler(String local) {
            this.local = local;
        }

        @Override
        protected void initChannel(SocketChannel ch) throws Exception {
            // 客戶端接收到的是httpResponse響應，所以要使用HttpResponseDecoder進行解碼
            ch.pipeline().addLast(new HttpResponseDecoder());
            // 客戶端發送的是httprequest，所以要使用HttpRequestEncoder進行編碼
            ch.pipeline().addLast(new HttpRequestEncoder());
            ch.pipeline().addLast(new ChunkedWriteHandler());
            ch.pipeline().addLast(new HttpDownloadHandler(local));
        }

    }
    public static void main(String[] args) throws Exception {
        HttpDownloadClient client = new HttpDownloadClient();
        //client.connect("127.0.0.1", 9003,"/file/pppp/1.doc","1.doc");
//        client.connect("zlysix.gree.com", 80, "http://zlysix.gree.com/HelloWeb/download/20m.apk", "20m.apk");
        client.connect("www.ghost64.com", 80, "http://www.ghost64.com/qqtupian/zixunImg/local/2017/05/27/1495855297602.jpg", "1495855297602.jpg");

    }
}

client端handler：

import java.io.File;
import java.io.FileOutputStream;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.codec.http.HttpContent;
//import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpResponse;
import io.netty.handler.codec.http.LastHttpContent;
import io.netty.util.internal.SystemPropertyUtil;
/**
 * @Author:yangyue
 * @Description:
 * @Date: Created in 9:15 on 2017/5/28.
 */

public class HttpDownloadHandler extends ChannelInboundHandlerAdapter {
    private boolean readingChunks = false; // 分塊讀取開關
    private FileOutputStream fOutputStream = null;// 文件輸出流
    private File localfile = null;// 下載文件的本地對象
    private String local = null;// 待下載文件名
    private int succCode;// 狀態碼

    public HttpDownloadHandler(String local) {
        this.local = local;
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        if (msg instanceof HttpResponse) {// response頭信息
            HttpResponse response = (HttpResponse) msg;
            succCode = response.getStatus().code();
            if (succCode == 200) {
                setDownLoadFile();// 設置下載文件
                readingChunks = true;
            }
            // System.out.println("CONTENT_TYPE:"
            // + response.headers().get(HttpHeaders.Names.CONTENT_TYPE));
        }
        if (msg instanceof HttpContent) {// response體信息
            HttpContent chunk = (HttpContent) msg;
            if (chunk instanceof LastHttpContent) {
                readingChunks = false;
            }

            ByteBuf buffer = chunk.content();
            byte[] dst = new byte[buffer.readableBytes()];
            if (succCode == 200) {
                while (buffer.isReadable()) {
                    buffer.readBytes(dst);
                    fOutputStream.write(dst);
                    buffer.release();
                }
                if (null != fOutputStream) {
                    fOutputStream.flush();
                }
            }

        }
        if (!readingChunks) {
            if (null != fOutputStream) {
                System.out.println("Download done->"+ localfile.getAbsolutePath());
                fOutputStream.flush();
                fOutputStream.close();
                localfile = null;
                fOutputStream = null;
            }
            ctx.channel().close();
        }
    }

    /**
     * 配置本地參數，准備下載
     */
    private void setDownLoadFile() throws Exception {
        if (null == fOutputStream) {
            local = SystemPropertyUtil.get("user.dir") + File.separator +local;
            //System.out.println(local);
            localfile = new File(local);
            if (!localfile.exists()) {
                localfile.createNewFile();
            }
            fOutputStream = new FileOutputStream(localfile);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
            throws Exception {
        System.out.println("管道異常：" + cause.getMessage());
        cause.printStackTrace();
        ctx.channel().close();
    }
}

這里客戶端我放的是網絡連接，下載的是一副圖片，啟動服務端和客戶端就可以看到這個圖片被下載到了工程的根目錄下。

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