public final class FileSystems extends Object
getDefault
method to get the default file system and factory methods to construct other types of file systems. The first invocation of any of the methods defined by this class causes the default provider
to be loaded. The default provider, identified by the URI scheme "file", creates the FileSystem
that provides access to the file systems accessible to the Java virtual machine. If the process of loading or initializing the default provider fails then an unspecified error is thrown.
The first invocation of the installedProviders
method, by way of invoking any of the
newFileSystem
methods defined by this class, locates and loads all installed file system providers. Installed providers are loaded using the service-provider loading facility defined by the ServiceLoader
class. Installed providers are loaded using the system class loader. If the system class loader cannot be found then the platform class loader is used. Providers are typically installed by placing them in a JAR file on the application class path, the JAR file contains a provider-configuration file named java.nio.file.spi.FileSystemProvider
in the resource directory META-INF/services
, and the file lists one or more fully-qualified names of concrete subclass of FileSystemProvider
that have a zero argument constructor. The ordering that installed providers are located is implementation specific. If a provider is instantiated and its getScheme
returns the same URI scheme of a provider that was previously instantiated then the most recently instantiated duplicate is discarded. URI schemes are compared without regard to case. 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.
This class also defines factory methods that allow a ClassLoader
to be specified when locating a provider. As with installed providers, the provider classes are identified by placing the provider configuration file in the resource directory META-INF/services
.
If a thread initiates the loading of the installed file system providers and another thread invokes a method that also attempts to load the providers then the method will block until the loading completes.
Modifier and Type | Method | Description |
---|---|---|
static FileSystem |
getDefault() |
Returns the default FileSystem . |
static FileSystem |
getFileSystem |
Returns a reference to an existing FileSystem . |
static FileSystem |
newFileSystem |
Constructs a new file system that is identified by a URI
|
static FileSystem |
newFileSystem |
Constructs a new file system that is identified by a URI
|
static FileSystem |
newFileSystem |
Constructs a new FileSystem to access the contents of a file as a file system. |
static FileSystem |
newFileSystem |
Constructs a new FileSystem to access the contents of a file as a file system. |
static FileSystem |
newFileSystem |
Constructs a new FileSystem to access the contents of a file as a file system. |
static FileSystem |
newFileSystem |
Constructs a new FileSystem to access the contents of a file as a file system. |
public static FileSystem getDefault()
FileSystem
. The default file system creates objects that provide access to the file systems accessible to the Java virtual machine. The working directory of the file system is the current user directory, named by the system property user.dir
. This allows for interoperability with the java.io.File
class. The first invocation of any of the methods defined by this class locates the default provider
object. Where the system property java.nio.file.spi.DefaultFileSystemProvider
is not defined then the default provider is a system-default provider that is invoked to create the default file system.
If the system property java.nio.file.spi.DefaultFileSystemProvider
is defined then it is taken to be a list of one or more fully-qualified names of concrete provider classes identified by the URI scheme "file"
. Where the property is a list of more than one name then the names are separated by a comma. Each class is loaded, using the system class loader, and instantiated by invoking a one argument constructor whose formal parameter type is FileSystemProvider
. The providers are loaded and instantiated in the order they are listed in the property. If this process fails or a provider's scheme is not equal to "file"
then an unspecified error is thrown. URI schemes are normally compared without regard to case but for the default provider, the scheme is required to be "file"
. The first provider class is instantiated by invoking it with a reference to the system-default provider. The second provider class is instantiated by invoking it with a reference to the first provider instance. The third provider class is instantiated by invoking it with a reference to the second instance, and so on. The last provider to be instantiated becomes the default provider; its
getFileSystem
method is invoked with the URI "file:///"
to get a reference to the default file system.
Subsequent invocations of this method return the file system that was returned by the first invocation.
public static FileSystem getFileSystem(URI uri)
FileSystem
. This method iterates over the installed
providers to locate the provider that is identified by the URI scheme
of the given URI. URI schemes are compared without regard to case. The exact form of the URI is highly provider dependent. If found, the provider's getFileSystem
method is invoked to obtain a reference to the
FileSystem
.
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.
uri
- the URI to locate the file systemIllegalArgumentException
- if the pre-conditions for the uri
parameter are not metFileSystemNotFoundException
- if the file system, identified by the URI, does not existProviderNotFoundException
- if a provider supporting the URI scheme is not installedSecurityException
- if a security manager is installed and it denies an unspecified permissionpublic static FileSystem newFileSystem(URI uri, Map<String,?> env) throws IOException
URI
This method iterates over the installed
providers to locate the provider that is identified by the URI scheme
of the given URI. URI schemes are compared without regard to case. The exact form of the URI is highly provider dependent. If found, the provider's newFileSystem(URI,Map)
method is invoked to construct the new file system.
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.
Usage Example: Suppose there is a provider identified by the scheme "memory"
installed:
FileSystem fs = FileSystems.newFileSystem(URI.create("memory:///?name=logfs"),
Map.of("capacity", "16G", "blockSize", "4k"));
uri
- the URI identifying the file systemenv
- a map of provider specific properties to configure the file system; may be emptyIllegalArgumentException
- if the pre-conditions for the uri
parameter are not met, or the env
parameter does not contain properties required by the provider, or a property value is invalidFileSystemAlreadyExistsException
- if the file system has already been createdProviderNotFoundException
- if a provider supporting the URI scheme is not installedIOException
- if an I/O error occurs creating the file systemSecurityException
- if a security manager is installed and it denies an unspecified permission required by the file system provider implementationpublic static FileSystem newFileSystem(URI uri, Map<String,?> env, ClassLoader loader) throws IOException
URI
This method first attempts to locate an installed provider in exactly the same manner as the newFileSystem(URI,Map)
method. If none of the installed providers support the URI scheme then an attempt is made to locate the provider using the given class loader. If a provider supporting the URI scheme is located then its newFileSystem(URI,Map)
is invoked to construct the new file system.
uri
- the URI identifying the file systemenv
- a map of provider specific properties to configure the file system; may be emptyloader
- the class loader to locate the provider or null
to only attempt to locate an installed providerIllegalArgumentException
- if the pre-conditions for the uri
parameter are not met, or the env
parameter does not contain properties required by the provider, or a property value is invalidFileSystemAlreadyExistsException
- if the URI scheme identifies an installed provider and the file system has already been createdProviderNotFoundException
- if a provider supporting the URI scheme is not foundServiceConfigurationError
- when an error occurs while loading a service providerIOException
- an I/O error occurs creating the file systemSecurityException
- if a security manager is installed and it denies an unspecified permission required by the file system provider implementationpublic static FileSystem newFileSystem(Path path, ClassLoader loader) throws IOException
FileSystem
to access the contents of a file as a file system. This method makes use of specialized providers that create pseudo file systems where the contents of one or more files is treated as a file system.
This method first attempts to locate an installed provider in exactly the same manner as the newFileSystem(Path, Map, ClassLoader)
method with an empty map. If none of the installed providers return a FileSystem
then an attempt is made to locate the provider using the given class loader. If a provider returns a file system then the lookup terminates and the file system is returned.
path
- the path to the fileloader
- the class loader to locate the provider or null
to only attempt to locate an installed providerProviderNotFoundException
- if a provider supporting this file type cannot be locatedServiceConfigurationError
- when an error occurs while loading a service providerIOException
- if an I/O error occursSecurityException
- if a security manager is installed and it denies an unspecified permissionpublic static FileSystem newFileSystem(Path path, Map<String,?> env) throws IOException
FileSystem
to access the contents of a file as a file system. This method makes use of specialized providers that create pseudo file systems where the contents of one or more files is treated as a file system.
This method first attempts to locate an installed provider in exactly the same manner as the newFileSystem(Path, Map, ClassLoader)
method. If found, the provider's newFileSystem(Path, Map)
method is invoked to construct the new file system.
path
- the path to the fileenv
- a map of provider specific properties to configure the file system; may be emptyProviderNotFoundException
- if a provider supporting this file type cannot be locatedServiceConfigurationError
- when an error occurs while loading a service providerIOException
- if an I/O error occursSecurityException
- if a security manager is installed and it denies an unspecified permissionpublic static FileSystem newFileSystem(Path path) throws IOException
FileSystem
to access the contents of a file as a file system. This method makes use of specialized providers that create pseudo file systems where the contents of one or more files is treated as a file system.
This method first attempts to locate an installed provider in exactly the same manner as the newFileSystem(Path, Map, ClassLoader)
method. If found, the provider's newFileSystem(Path, Map)
method is invoked with an empty map to construct the new file system.
path
- the path to the fileProviderNotFoundException
- if a provider supporting this file type cannot be locatedServiceConfigurationError
- when an error occurs while loading a service providerIOException
- if an I/O error occursSecurityException
- if a security manager is installed and it denies an unspecified permissionpublic static FileSystem newFileSystem(Path path, Map<String,?> env, ClassLoader loader) throws IOException
FileSystem
to access the contents of a file as a file system. This method makes use of specialized providers that create pseudo file systems where the contents of one or more files is treated as a file system.
This method iterates over the installed
providers. It invokes, in turn, each provider's newFileSystem(Path,Map)
method. If a provider returns a file system then the iteration terminates and the file system is returned. If none of the installed providers return a FileSystem
then an attempt is made to locate the provider using the given class loader. If a provider returns a file system, then the lookup terminates and the file system is returned.
path
- the path to the fileenv
- a map of provider specific properties to configure the file system; may be emptyloader
- the class loader to locate the provider or null
to only attempt to locate an installed providerProviderNotFoundException
- if a provider supporting this file type cannot be locatedServiceConfigurationError
- when an error occurs while loading a service providerIOException
- if an I/O error occursSecurityException
- if a security manager is installed and it denies an unspecified permission
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