java.nio.file.spi

Class FileSystemProvider

Inhaltsverzeichnis

  • public abstract class FileSystemProvider
extends Object
    Service-provider class for file systems. The methods defined by the Files class will typically delegate to an instance of this class.

    A file system provider is a concrete implementation of this class that implements the abstract methods defined by this class. A provider is identified by a URI scheme. The default provider is identified by the URI scheme "file". It creates the FileSystem that provides access to the file systems accessible to the Java virtual machine. The FileSystems class defines how file system providers are located and loaded. The default provider is typically a system-default provider but may be overridden if the system property java.nio.file.spi.DefaultFileSystemProvider is set. In that case, the provider has a one argument constructor whose formal parameter type is FileSystemProvider. All other providers have a zero argument constructor that initializes the provider.

    A provider is a factory for one or more FileSystem instances. Each file system is identified by a URI where the URI's scheme matches the provider's scheme. The default file system, for example, is identified by the URI "file:///". A memory-based file system, for example, may be identified by a URI such as "memory:///?name=logfs". The newFileSystem method may be used to create a file system, and the getFileSystem method may be used to obtain a reference to an existing file system created by the provider. Where a provider is the factory for a single file system then it is provider dependent if the file system is created when the provider is initialized, or later when the newFileSystem method is invoked. In the case of the default provider, the FileSystem is created when the provider is initialized.

    All of the methods in this class are safe for use by multiple concurrent threads.

    Since:
    1.7

    • Constructor Detail

      • FileSystemProvider

        protected FileSystemProvider()
        Initializes a new instance of this class.

        During construction a provider may safely access files associated with the default provider but care needs to be taken to avoid circular loading of other installed providers. If circular loading of installed providers is detected then an unspecified error is thrown.

        Throws:
        SecurityException - If a security manager has been installed and it denies RuntimePermission("fileSystemProvider")

    • Method Detail

      • installedProviders

        public static List<FileSystemProvider> installedProviders()
        Returns a list of the installed file system providers.

        The first invocation of this method causes the default provider to be initialized (if not already initialized) and loads any other installed providers as described by the FileSystems class.

        Returns:
        An unmodifiable list of the installed file system providers. The list contains at least one element, that is the default file system provider
        Throws:
        ServiceConfigurationError - When an error occurs while loading a service provider

      • getScheme

        public abstract String getScheme()
        Returns the URI scheme that identifies this provider.
        Returns:
        The URI scheme

      • newFileSystem

        public abstract FileSystem newFileSystem(URI uri,
                       Map<String,?> env)
                                  throws IOException
        Constructs a new FileSystem object identified by a URI. This method is invoked by the FileSystems.newFileSystem(URI,Map) method to open a new file system identified by a URI.

        The uri parameter is an absolute, hierarchical URI, with a scheme equal (without regard to case) to the scheme supported by this provider. The exact form of the URI is highly provider dependent. The env parameter is a map of provider specific properties to configure the file system.

        This method throws FileSystemAlreadyExistsException if the file system already exists because it was previously created by an invocation of this method. Once a file system is closed it is provider-dependent if the provider allows a new file system to be created with the same URI as a file system it previously created.

        Parameters:
        uri - URI reference
        env - A map of provider specific properties to configure the file system; may be empty
        Returns:
        A new file system
        Throws:
        IllegalArgumentException - If the pre-conditions for the uri parameter aren't met, or the env parameter does not contain properties required by the provider, or a property value is invalid
        IOException - An I/O error occurs creating the file system
        SecurityException - If a security manager is installed and it denies an unspecified permission required by the file system provider implementation
        FileSystemAlreadyExistsException - If the file system has already been created

      • getFileSystem

        public abstract FileSystem getFileSystem(URI uri)
        Returns an existing FileSystem created by this provider.

        This method returns a reference to a FileSystem that was created by invoking the newFileSystem(URI,Map) method. File systems created the newFileSystem(Path,Map) method are not returned by this method. The file system is identified by its URI. Its exact form is highly provider dependent. In the case of the default provider the URI's path component is "/" and the authority, query and fragment components are undefined (Undefined components are represented by null).

        Once a file system created by this provider is closed it is provider-dependent if this method returns a reference to the closed file system or throws FileSystemNotFoundException. If the provider allows a new file system to be created with the same URI as a file system it previously created then this method throws the exception if invoked after the file system is closed (and before a new instance is created by the newFileSystem method).

        If a security manager is installed then a provider implementation may require to check a permission before returning a reference to an existing file system. In the case of the default file system, no permission check is required.

        Parameters:
        uri - URI reference
        Returns:
        The file system
        Throws:
        IllegalArgumentException - If the pre-conditions for the uri parameter aren't met
        FileSystemNotFoundException - If the file system does not exist
        SecurityException - If a security manager is installed and it denies an unspecified permission.

      • getPath

        public abstract Path getPath(URI uri)
        Return a Path object by converting the given URI. The resulting Path is associated with a FileSystem that already exists or is constructed automatically.

        The exact form of the URI is file system provider dependent. In the case of the default provider, the URI scheme is "file" and the given URI has a non-empty path component, and undefined query, and fragment components. The resulting Path is associated with the default default FileSystem.

        If a security manager is installed then a provider implementation may require to check a permission. In the case of the default file system, no permission check is required.

        Parameters:
        uri - The URI to convert
        Throws:
        IllegalArgumentException - If the URI scheme does not identify this provider or other preconditions on the uri parameter do not hold
        FileSystemNotFoundException - The file system, identified by the URI, does not exist and cannot be created automatically
        SecurityException - If a security manager is installed and it denies an unspecified permission.

      • newFileSystem

        public FileSystem newFileSystem(Path path,
                       Map<String,?> env)
                         throws IOException
        Constructs a new FileSystem to access the contents of a file as a file system.

        This method is intended for specialized providers of pseudo file systems where the contents of one or more files is treated as a file system. The env parameter is a map of provider specific properties to configure the file system.

        If this provider does not support the creation of such file systems or if the provider does not recognize the file type of the given file then it throws UnsupportedOperationException. The default implementation of this method throws UnsupportedOperationException.

        Parameters:
        path - The path to the file
        env - A map of provider specific properties to configure the file system; may be empty
        Returns:
        A new file system
        Throws:
        UnsupportedOperationException - If this provider does not support access to the contents as a file system or it does not recognize the file type of the given file
        IllegalArgumentException - If the env parameter does not contain properties required by the provider, or a property value is invalid
        IOException - If an I/O error occurs
        SecurityException - If a security manager is installed and it denies an unspecified permission.

      • newFileChannel

        public FileChannel newFileChannel(Path path,
                         Set<? extends OpenOption> options,
                         FileAttribute<?>... attrs)
                           throws IOException
        Opens or creates a file for reading and/or writing, returning a file channel to access the file. This method works in exactly the manner specified by the FileChannel.open method. A provider that does not support all the features required to construct a file channel throws UnsupportedOperationException. The default provider is required to support the creation of file channels. When not overridden, the default implementation throws UnsupportedOperationException.
        Parameters:
        path - the path of the file to open or create
        options - options specifying how the file is opened
        attrs - an optional list of file attributes to set atomically when creating the file
        Returns:
        a new file channel
        Throws:
        IllegalArgumentException - If the set contains an invalid combination of options
        UnsupportedOperationException - If this provider that does not support creating file channels, or an unsupported open option or file attribute is specified
        IOException - If an I/O error occurs
        SecurityException - In the case of the default file system, the SecurityManager.checkRead(String) method is invoked to check read access if the file is opened for reading. The SecurityManager.checkWrite(String) method is invoked to check write access if the file is opened for writing

      • newAsynchronousFileChannel

        public AsynchronousFileChannel newAsynchronousFileChannel(Path path,
                                                 Set<? extends OpenOption> options,
                                                 ExecutorService executor,
                                                 FileAttribute<?>... attrs)
                                                   throws IOException
        Opens or creates a file for reading and/or writing, returning an asynchronous file channel to access the file. This method works in exactly the manner specified by the AsynchronousFileChannel.open method. A provider that does not support all the features required to construct an asynchronous file channel throws UnsupportedOperationException. The default provider is required to support the creation of asynchronous file channels. When not overridden, the default implementation of this method throws UnsupportedOperationException.
        Parameters:
        path - the path of the file to open or create
        options - options specifying how the file is opened
        executor - the thread pool or null to associate the channel with the default thread pool
        attrs - an optional list of file attributes to set atomically when creating the file
        Returns:
        a new asynchronous file channel
        Throws:
        IllegalArgumentException - If the set contains an invalid combination of options
        UnsupportedOperationException - If this provider that does not support creating asynchronous file channels, or an unsupported open option or file attribute is specified
        IOException - If an I/O error occurs
        SecurityException - In the case of the default file system, the SecurityManager.checkRead(String) method is invoked to check read access if the file is opened for reading. The SecurityManager.checkWrite(String) method is invoked to check write access if the file is opened for writing

      • newByteChannel

        public abstract SeekableByteChannel newByteChannel(Path path,
                                 Set<? extends OpenOption> options,
                                 FileAttribute<?>... attrs)
                                            throws IOException
        Opens or creates a file, returning a seekable byte channel to access the file. This method works in exactly the manner specified by the Files.newByteChannel(Path,Set,FileAttribute[]) method.
        Parameters:
        path - the path to the file to open or create
        options - options specifying how the file is opened
        attrs - an optional list of file attributes to set atomically when creating the file
        Returns:
        a new seekable byte channel
        Throws:
        IllegalArgumentException - if the set contains an invalid combination of options
        UnsupportedOperationException - if an unsupported open option is specified or the array contains attributes that cannot be set atomically when creating the file
        FileAlreadyExistsException - if a file of that name already exists and the CREATE_NEW option is specified (optional specific exception)
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the path if the file is opened for reading. The checkWrite method is invoked to check write access to the path if the file is opened for writing. The checkDelete method is invoked to check delete access if the file is opened with the DELETE_ON_CLOSE option.
      • public void createLink(Path link,
              Path existing)
                throws IOException
        Creates a new link (directory entry) for an existing file. This method works in exactly the manner specified by the Files.createLink(java.nio.file.Path, java.nio.file.Path) method.

        The default implementation of this method throws UnsupportedOperationException.

        Parameters:
        link - the link (directory entry) to create
        existing - a path to an existing file
        Throws:
        UnsupportedOperationException - if the implementation does not support adding an existing file to a directory
        FileAlreadyExistsException - if the entry could not otherwise be created because a file of that name already exists (optional specific exception)
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, it denies LinkPermission("hard") or its checkWrite method denies write access to either the link or the existing file.

      • deleteIfExists

        public boolean deleteIfExists(Path path)
                       throws IOException
        Deletes a file if it exists. This method works in exactly the manner specified by the Files.deleteIfExists(java.nio.file.Path) method.

        The default implementation of this method simply invokes delete(java.nio.file.Path) ignoring the NoSuchFileException when the file does not exist. It may be overridden where appropriate.

        Parameters:
        path - the path to the file to delete
        Returns:
        true if the file was deleted by this method; false if the file could not be deleted because it did not exist
        Throws:
        DirectoryNotEmptyException - if the file is a directory and could not otherwise be deleted because the directory is not empty (optional specific exception)
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, the SecurityManager.checkDelete(String) method is invoked to check delete access to the file
      • public Path readSymbolicLink(Path link)
                      throws IOException
        Reads the target of a symbolic link. This method works in exactly the manner specified by the Files.readSymbolicLink(java.nio.file.Path) method.

        The default implementation of this method throws UnsupportedOperationException.

        Parameters:
        link - the path to the symbolic link
        Throws:
        UnsupportedOperationException - if the implementation does not support symbolic links
        NotLinkException - if the target could otherwise not be read because the file is not a symbolic link (optional specific exception)
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, it checks that FilePermission has been granted with the "readlink" action to read the link.

      • copy

        public abstract void copy(Path source,
        Path target,
        CopyOption... options)
                   throws IOException
        Copy a file to a target file. This method works in exactly the manner specified by the Files.copy(Path,Path,CopyOption[]) method except that both the source and target paths must be associated with this provider.
        Parameters:
        source - the path to the file to copy
        target - the path to the target file
        options - options specifying how the copy should be done
        Throws:
        UnsupportedOperationException - if the array contains a copy option that is not supported
        FileAlreadyExistsException - if the target file exists but cannot be replaced because the REPLACE_EXISTING option is not specified (optional specific exception)
        DirectoryNotEmptyException - the REPLACE_EXISTING option is specified but the file cannot be replaced because it is a non-empty directory (optional specific exception)
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the source file, the checkWrite is invoked to check write access to the target file. If a symbolic link is copied the security manager is invoked to check LinkPermission("symbolic").

      • move

        public abstract void move(Path source,
        Path target,
        CopyOption... options)
                   throws IOException
        Move or rename a file to a target file. This method works in exactly the manner specified by the Files.move(java.nio.file.Path, java.nio.file.Path, java.nio.file.CopyOption...) method except that both the source and target paths must be associated with this provider.
        Parameters:
        source - the path to the file to move
        target - the path to the target file
        options - options specifying how the move should be done
        Throws:
        UnsupportedOperationException - if the array contains a copy option that is not supported
        FileAlreadyExistsException - if the target file exists but cannot be replaced because the REPLACE_EXISTING option is not specified (optional specific exception)
        DirectoryNotEmptyException - the REPLACE_EXISTING option is specified but the file cannot be replaced because it is a non-empty directory (optional specific exception)
        AtomicMoveNotSupportedException - if the options array contains the ATOMIC_MOVE option but the file cannot be moved as an atomic file system operation.
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, the checkWrite method is invoked to check write access to both the source and target file.

      • isSameFile

        public abstract boolean isSameFile(Path path,
                 Path path2)
                            throws IOException
        Tests if two paths locate the same file. This method works in exactly the manner specified by the Files.isSameFile(java.nio.file.Path, java.nio.file.Path) method.
        Parameters:
        path - one path to the file
        path2 - the other path
        Returns:
        true if, and only if, the two paths locate the same file
        Throws:
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to both files.

      • isHidden

        public abstract boolean isHidden(Path path)
                          throws IOException
        Tells whether or not a file is considered hidden. This method works in exactly the manner specified by the Files.isHidden(java.nio.file.Path) method.

        This method is invoked by the isHidden method.

        Parameters:
        path - the path to the file to test
        Returns:
        true if the file is considered hidden
        Throws:
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the file.

      • getFileStore

        public abstract FileStore getFileStore(Path path)
                                throws IOException
        Returns the FileStore representing the file store where a file is located. This method works in exactly the manner specified by the Files.getFileStore(java.nio.file.Path) method.
        Parameters:
        path - the path to the file
        Returns:
        the file store where the file is stored
        Throws:
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the file, and in addition it checks RuntimePermission ("getFileStoreAttributes")

      • checkAccess

        public abstract void checkAccess(Path path,
               AccessMode... modes)
                          throws IOException
        Checks the existence, and optionally the accessibility, of a file.

        This method may be used by the isReadable, isWritable and isExecutable methods to check the accessibility of a file.

        This method checks the existence of a file and that this Java virtual machine has appropriate privileges that would allow it access the file according to all of access modes specified in the modes parameter as follows:

        Value Description
        READ Checks that the file exists and that the Java virtual machine has permission to read the file.
        WRITE Checks that the file exists and that the Java virtual machine has permission to write to the file,
        EXECUTE Checks that the file exists and that the Java virtual machine has permission to execute the file. The semantics may differ when checking access to a directory. For example, on UNIX systems, checking for EXECUTE access checks that the Java virtual machine has permission to search the directory in order to access file or subdirectories.

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        If the modes parameter is of length zero, then the existence of the file is checked.

        This method follows symbolic links if the file referenced by this object is a symbolic link. Depending on the implementation, this method may require to read file permissions, access control lists, or other file attributes in order to check the effective access to the file. To determine the effective access to a file may require access to several attributes and so in some implementations this method may not be atomic with respect to other file system operations.

        Parameters:
        path - the path to the file to check
        modes - The access modes to check; may have zero elements
        Throws:
        UnsupportedOperationException - an implementation is required to support checking for READ, WRITE, and EXECUTE access. This exception is specified to allow for the Access enum to be extended in future releases.
        NoSuchFileException - if a file does not exist (optional specific exception)
        AccessDeniedException - the requested access would be denied or the access cannot be determined because the Java virtual machine has insufficient privileges or other reasons. (optional specific exception)
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, the checkRead is invoked when checking read access to the file or only the existence of the file, the checkWrite is invoked when checking write access to the file, and checkExec is invoked when checking execute access.

      • readAttributes

        public abstract Map<String,Object> readAttributes(Path path,
                                String attributes,
                                LinkOption... options)
                                           throws IOException
        Reads a set of file attributes as a bulk operation. This method works in exactly the manner specified by the Files.readAttributes(Path,String,LinkOption[]) method.
        Parameters:
        path - the path to the file
        attributes - the attributes to read
        options - options indicating how symbolic links are handled
        Returns:
        a map of the attributes returned; may be empty. The map's keys are the attribute names, its values are the attribute values
        Throws:
        UnsupportedOperationException - if the attribute view is not available
        IllegalArgumentException - if no attributes are specified or an unrecognized attributes is specified
        IOException - If an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, its checkRead method denies read access to the file. If this method is invoked to read security sensitive attributes then the security manager may be invoke to check for additional permissions.

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Dokument erstellt 11/06/2005, zuletzt geändert 04/03/2020
Quelle des gedruckten Dokuments:https://www.gaudry.be/de/java-api-rf-java/nio/file/spi/filesystemprovider.html

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