Netty 輕松實(shí)現(xiàn)文件上傳功能

更新時(shí)間：2021年07月06日 15:28:28 作者：Java技術(shù)棧

今天我們來完成一個(gè)使用netty進(jìn)行文件傳輸?shù)娜蝿?wù)。在實(shí)際項(xiàng)目中，文件傳輸通常采用FTP或者HTTP附件的方式，對(duì)Netty 文件上傳功能感興趣的朋友一起看看吧

今天我們來完成一個(gè)使用netty進(jìn)行文件傳輸?shù)娜蝿?wù)。在實(shí)際項(xiàng)目中，文件傳輸通常采用FTP或者HTTP附件的方式。事實(shí)上通過TCP Socket+File的方式進(jìn)行文件傳輸也有一定的應(yīng)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(duì)兩個(gè)跨主機(jī)的JVM進(jìn)程之間進(jìn)行持久化數(shù)據(jù)的相互交換。

而使用netty來進(jìn)行文件傳輸也是利用netty天然的優(yōu)勢：零拷貝功能。很多同學(xué)都聽說過netty的”零拷貝”功能，但是具體體現(xiàn)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(xiàn)在如下三個(gè)方面：

Netty的接收和發(fā)送ByteBuffer采用DIRECT BUFFERS，使用堆外直接內(nèi)存進(jìn)行Socket讀寫，不需要進(jìn)行字節(jié)緩沖區(qū)的二次拷貝。如果使用傳統(tǒng)的堆內(nèi)存（HEAP BUFFERS）進(jìn)行Socket讀寫，JVM會(huì)將堆內(nèi)存Buffer拷貝一份到直接內(nèi)存中，然后才寫入Socket中。相比于堆外直接內(nèi)存，消息在發(fā)送過程中多了一次緩沖區(qū)的內(nèi)存拷貝。
Netty提供了組合Buffer對(duì)象，可以聚合多個(gè)ByteBuffer對(duì)象，用戶可以像操作一個(gè)Buffer那樣方便的對(duì)組合Buffer進(jìn)行操作，避免了傳統(tǒng)通過內(nèi)存拷貝的方式將幾個(gè)小Buffer合并成一個(gè)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(qū)的數(shù)據(jù)發(fā)送到目標(biāo)Channel，避免了傳統(tǒng)通過循環(huán)write方式導(dǎo)致的內(nèi)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(guān)文檔。我們還是把重點(diǎn)放在文件傳輸上。Netty作為高性能的服務(wù)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(wǎng)頁上傳文件寫入服務(wù)器，當(dāng)然要使用http的形式那你也用不著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j(luò)ar包：okhttp。使用該jar完成http請(qǐng)求的發(fā)送。但是在netty5 中已經(jīng)為我們寫好了，我們可以直接調(diào)用netty5的API就可以實(shí)現(xiàn)。所以netty4和5的差別還是挺大的，至于使用哪個(gè)，那就看你們公司選擇哪一個(gè)了！本文目前使用netty4來實(shí)現(xiàn)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(jīng)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(jīng)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(gè)對(duì)象，用于統(tǒng)計(jì)文件上傳進(jìn)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(jié)數(shù)組
    private int endPos;// 結(jié)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(jīng)讀完--------0

Process finished with exit code 0

這樣就實(shí)現(xiàn)了服務(wù)器端文件的上傳，當(dāng)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(jiān)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用于監(jiān)視發(fā)送數(shù)據(jù)的狀態(tài)
        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(wù)器下載直接填寫要下載的文件的相對(duì)路徑
     *        （↑↑↑建議只使用字母和數(shù)字對(duì)特殊字符對(duì)字符進(jìn)行部分過濾可能導(dǎo)致異常↑↑↑）
     *        向互聯(lián)網(wǎng)下載輸入完整路徑
     * @param host 目的主機(jī)ip或域名
     * @param port 目標(biāo)主機(jī)端口
     * @param url 文件路徑
     * @param local 本地存儲(chǔ)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(gòu)建http請(qǐng)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(fā)送http請(qǐng)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(yīng)，所以要使用HttpResponseDecoder進(jìn)行解碼
            ch.pipeline().addLast(new HttpResponseDecoder());
            // 客戶端發(fā)送的是httprequest，所以要使用HttpRequestEncoder進(jìn)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(guān)
    private FileOutputStream fOutputStream = null;// 文件輸出流
    private File localfile = null;// 下載文件的本地對(duì)象
    private String local = null;// 待下載文件名
    private int succCode;// 狀態(tài)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(shè)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(shù)，準(zhǔn)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(wǎng)絡(luò)連接，下載的是一副圖片，啟動(dòng)服務(wù)端和客戶端就可以看到這個(gè)圖片被下載到了工程的根目錄下。