java.nio.file.StandardOpenOption#READ源码实例Demo

static OpenOptions forNewInputStream(Collection<? extends OpenOption> options) {
    if (options.isEmpty()) {
        return new OpenOptions(true, false, false, false, false, false, Collections.<OpenOption>emptySet());
    }

    boolean deleteOnClose = false;

    for (OpenOption option : options) {
        if (option == StandardOpenOption.DELETE_ON_CLOSE) {
            deleteOnClose = true;
        } else if (option != StandardOpenOption.READ && option != StandardOpenOption.TRUNCATE_EXISTING && !isIgnoredOpenOption(option)) {
            // TRUNCATE_EXISTING is ignored in combination with READ
            throw Messages.fileSystemProvider().unsupportedOpenOption(option);
        }
    }

    return new OpenOptions(true, false, false, false, false, deleteOnClose, options);
}
 

/**
 * @throws Exception If failed.
 */
@Test
public void dumpRawPageHistoryToDefaultDir() throws Exception {
    diagnosticProcessor.dumpPageHistory(new PageHistoryDiagnoster.DiagnosticPageBuilder()
        .pageIds(expectedPageId)
        .addAction(PRINT_TO_RAW_FILE)
    );

    Path path = Paths.get(U.defaultWorkDirectory(), DEFAULT_TARGET_FOLDER);
    File dumpFile = path.toFile().listFiles((dir, name) -> name.endsWith(RAW_FILE_FORMAT))[0];

    try (SegmentIO io = new SegmentIO(0L, new RandomAccessFileIO(dumpFile, StandardOpenOption.READ))) {
        SegmentHeader hdr = RecordV1Serializer.readSegmentHeader(io, new SimpleSegmentFileInputFactory());

        assertFalse(hdr.isCompacted());

        assertEquals(RecordSerializerFactory.LATEST_SERIALIZER_VERSION, hdr.getSerializerVersion());
    }
}
 

public void sendFile() {
	if (this.selectedPeer == null) return;
	
	FileDialog fd = new FileDialog(shlSimpleChatExample, SWT.OPEN);
       fd.setText("Choose a file to send");
       String selected = fd.open();

       if (selected == null) return;
       
       Path path = FileSystems.getDefault().getPath(selected);
       OpenOption[] read = { StandardOpenOption.READ };
       try {
		FileChannel fileChannel = FileChannel.open(path, read);
				
		this.selectedPeer.sendFile(fileChannel, path.getFileName().toString(), (int)fileChannel.size());
       } catch (IOException e) {
		e.printStackTrace();
	}
}
 

/**
 * Convert Java open options to native flags.
 *
 * @param modes java options.
 * @param log logger.
 * @param enableDirect flag for enabling option {@link IgniteNativeIoLib#O_DIRECT} .
 * @return native flags for open method.
 */
private static int setupOpenFlags(OpenOption[] modes, IgniteLogger log, boolean enableDirect) {
    int flags = enableDirect ? IgniteNativeIoLib.O_DIRECT : 0;
    List<OpenOption> openOptionList = Arrays.asList(modes);

    for (OpenOption mode : openOptionList) {
        if (mode == StandardOpenOption.READ) {
            flags |= openOptionList.contains(StandardOpenOption.WRITE)
                ? IgniteNativeIoLib.O_RDWR
                : IgniteNativeIoLib.O_RDONLY;
        }
        else if (mode == StandardOpenOption.WRITE) {
            flags |= openOptionList.contains(StandardOpenOption.READ)
                ? IgniteNativeIoLib.O_RDWR
                : IgniteNativeIoLib.O_WRONLY;
        }
        else if (mode == StandardOpenOption.CREATE)
            flags |= IgniteNativeIoLib.O_CREAT;
        else if (mode == StandardOpenOption.TRUNCATE_EXISTING)
            flags |= IgniteNativeIoLib.O_TRUNC;
        else if (mode == StandardOpenOption.SYNC)
            flags |= IgniteNativeIoLib.O_SYNC;
        else
            log.error("Unsupported open option [" + mode + "]");
    }

    return flags;
}
 

/**
 * Returns the reader if it is not closed, or thrown an exception otherwise.
 */
private Reader reader() throws DataStoreException {
    final Reader r = reader;
    if (r == null) {
        throw new DataStoreClosedException(getLocale(), Constants.GEOTIFF, StandardOpenOption.READ);
    }
    return r;
}
 

/**
 * Opens or creates a file, returning an output stream that may be used to
 * write bytes to the file. This method works in exactly the manner
 * specified by the {@link Files#newOutputStream} method.
 *
 * <p> The default implementation of this method opens a channel to the file
 * as if by invoking the {@link #newByteChannel} method and constructs a
 * stream that writes bytes to the channel. This method should be overridden
 * where appropriate.
 *
 * @param   path
 *          the path to the file to open or create
 * @param   options
 *          options specifying how the file is opened
 *
 * @return  a new output stream
 *
 * @throws  IllegalArgumentException
 *          if {@code options} contains an invalid combination of options
 * @throws  UnsupportedOperationException
 *          if an unsupported option is specified
 * @throws  IOException
 *          if an I/O error occurs
 * @throws  SecurityException
 *          In the case of the default provider, and a security manager is
 *          installed, the {@link SecurityManager#checkWrite(String) checkWrite}
 *          method is invoked to check write access to the file. The {@link
 *          SecurityManager#checkDelete(String) checkDelete} method is
 *          invoked to check delete access if the file is opened with the
 *          {@code DELETE_ON_CLOSE} option.
 */
public OutputStream newOutputStream(Path path, OpenOption... options)
    throws IOException
{
    int len = options.length;
    Set<OpenOption> opts ;
    if (len == 0) {
        opts = DEFAULT_OPEN_OPTIONS;
    } else {
        opts = new HashSet<>();
        for (OpenOption opt: options) {
            if (opt == StandardOpenOption.READ)
                throw new IllegalArgumentException("READ not allowed");
            opts.add(opt);
        }
        opts.add(StandardOpenOption.WRITE);
    }
    WritableByteChannel wbc = newByteChannel(path, opts);
    if (wbc instanceof FileChannelImpl) {
        ((FileChannelImpl) wbc).setUninterruptible();
    }
    return Channels.newOutputStream(wbc);
}
 

static OpenOptions forNewByteChannel(Set<? extends OpenOption> options) {

        boolean read = false;
        boolean write = false;
        boolean append = false;
        boolean truncateExisting = false;
        boolean create = false;
        boolean createNew = false;
        boolean deleteOnClose = false;

        for (OpenOption option : options) {
            if (option == StandardOpenOption.READ) {
                read = true;
            } else if (option == StandardOpenOption.WRITE) {
                write = true;
            } else if (option == StandardOpenOption.APPEND) {
                append = true;
            } else if (option == StandardOpenOption.TRUNCATE_EXISTING) {
                truncateExisting = true;
            } else if (option == StandardOpenOption.CREATE) {
                create = true;
            } else if (option == StandardOpenOption.CREATE_NEW) {
                createNew = true;
            } else if (option == StandardOpenOption.DELETE_ON_CLOSE) {
                deleteOnClose = true;
            } else if (!isIgnoredOpenOption(option)) {
                throw Messages.fileSystemProvider().unsupportedOpenOption(option);
            }
        }

        // as per Files.newByteChannel, if none of these options is given, default to read
        if (!read && !write && !append) {
            read = true;
        }

        // read contradicts with write, append, create and createNew; TRUNCATE_EXISTING is ignored in combination with READ
        if (read && (write || append || create || createNew)) {
            throw Messages.fileSystemProvider().illegalOpenOptionCombination(options);
        }

        // append and truncateExisting contract each other
        if (append && truncateExisting) {
            throw Messages.fileSystemProvider().illegalOpenOptionCombination(options);
        }

        // read and write contract each other; read and append contract each other; append and truncateExisting contract each other
        if ((read && write) || (read && append) || (append && truncateExisting)) {
            throw Messages.fileSystemProvider().illegalOpenOptionCombination(options);
        }

        return new OpenOptions(read, write, append, create, createNew, deleteOnClose, options);
    }