Transfer a file

问题

I can not figure out how to transfer files using async and future. I have the code, when I run this code, getting of a files is working, but transfer a files don't work.

Server

package test3;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

public class server3 {
private static final int PORT = 1234;
private static final String FILE_NAME = "2.jpg"; 

private static class Storage {
    private final AsynchronousFileChannel fileChannel;
    private Future<Integer> writeOperation, readOperation;
    private long positionWrite, positionRead;
    long counter =0;

    Storage() throws IOException {
        fileChannel = AsynchronousFileChannel.open(Paths.get(FILE_NAME),
                StandardOpenOption.CREATE,
                StandardOpenOption.WRITE,
                StandardOpenOption.READ);
    }

    void fileReadAndWrite(ByteBuffer buffer, SocketChannel socketChannel)
            throws InterruptedException, ExecutionException, IOException {
        try {
            if (readOperation != null)
                positionRead += readOperation.get(5, TimeUnit.SECONDS);

            readOperation = fileChannel.read(buffer, positionRead);

            buffer.flip();

            socketChannel.write(buffer);

        } catch (TimeoutException exc) {
            close();
            System.out.println("Read timeout");
        }
    }

    void write(ByteBuffer buffer) throws InterruptedException, ExecutionException {
        try {
            if (writeOperation != null)
                positionWrite += writeOperation.get(5, TimeUnit.SECONDS);
            writeOperation = fileChannel.write(buffer, positionWrite);
        } catch (TimeoutException exc) {
            close();
            System.err.println("Write timeout");
        }
    }

    void close() {
        try {
            fileChannel.close();
        } catch (IOException exc) {
            exc.printStackTrace();
        }
    }
}

public static void main(String args[]) throws Exception {
    Selector selector = Selector.open();
    try (ServerSocketChannel serverSocketChannel = ServerSocketChannel.open()) {
        serverSocketChannel.bind(new InetSocketAddress(PORT));
        serverSocketChannel.configureBlocking(false);
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        while (true) {
            selector.select();
            Set<SelectionKey> keys = selector.selectedKeys();
            Iterator<SelectionKey> iterator = keys.iterator();
            while (iterator.hasNext()) {
                SelectionKey key = iterator.next();

                if (key.isAcceptable()) {
                    SocketChannel socketChannel = serverSocketChannel.accept();
                    socketChannel.configureBlocking(false);
                    socketChannel.register(selector, SelectionKey.OP_WRITE | SelectionKey.OP_READ,
                            new Storage());

                    System.out.println("isAcceptable");

                }
                if (key.isReadable()) {
                    System.out.println("isReadable");
                    SocketChannel socketChannel = (SocketChannel) key.channel();
                    Storage storage = (Storage) key.attachment();
                    ByteBuffer buffer = ByteBuffer.allocate(256);

                    int read = socketChannel.read(buffer);
                    if (read != -1) {
                        buffer.flip();
                        storage.write(buffer);
                    } else {
                        storage.close();
                        socketChannel.close();
                    }
                }

                if (key.isWritable()) {
                    Storage storage = (Storage) key.attachment();
                    SocketChannel socketChannel = (SocketChannel) key.channel();
                    ByteBuffer buffer = ByteBuffer.allocate(1024);

                    if (storage.fileChannel.size() >= storage.readOperation) {
                        storage.fileReadAndWrite(buffer, socketChannel);
                    } else {
                        storage.close();
                        socketChannel.close();
                    }
                }
            }

            iterator.remove();
        }
    }
}

}

Client

package test.test1;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.*;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
public class client_test1 {

private static final int PORT = 1234;
private static final String HOST = "localhost";
private static final String FILE_NAME = "3.jpg";


private static InetSocketAddress serverAddress = new InetSocketAddress(HOST, PORT);

public static void main(String[] args) {
    try (SocketChannel socketChannel = SocketChannel.open(serverAddress)) {
        try (FileChannel fileChannel = FileChannel.open(
                Paths.get(FILE_NAME), StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
            fileChannel.transferFrom(socketChannel, 0, Long.MAX_VALUE);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

}

If the channel is ready to receive new files, run this line if (key.isWritable()). This line if (storage.counter != 30) is wrong. This line call until the file is transferred. I don't understand how to transfer a file. Help, please.

来源：https://stackoverflow.com/questions/50112763/transfer-a-file