Class FileSystems
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.
- Since:
- 1.7
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Method Summary
Modifier and TypeMethodDescriptionstatic FileSystem
Returns the defaultFileSystem
.static FileSystem
getFileSystem
(URI uri) Returns a reference to an existingFileSystem
.static FileSystem
newFileSystem
(URI uri, Map<String, ?> env) Constructs a new file system that is identified by aURI
static FileSystem
newFileSystem
(URI uri, Map<String, ?> env, ClassLoader loader) Constructs a new file system that is identified by aURI
static FileSystem
newFileSystem
(Path path) Constructs a newFileSystem
to access the contents of a file as a file system.static FileSystem
newFileSystem
(Path path, ClassLoader loader) Constructs a newFileSystem
to access the contents of a file as a file system.static FileSystem
newFileSystem
(Path path, Map<String, ?> env) Constructs a newFileSystem
to access the contents of a file as a file system.static FileSystem
newFileSystem
(Path path, Map<String, ?> env, ClassLoader loader) Constructs a newFileSystem
to access the contents of a file as a file system.
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Method Details
-
getDefault
Returns the defaultFileSystem
. 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 propertyuser.dir
. This allows for interoperability with thejava.io.File
class.The first invocation of any of the methods defined by this class locates the default
provider
object. Where the system propertyjava.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 isFileSystemProvider
. 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; itsgetFileSystem
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.
- Returns:
- the default file system
-
getFileSystem
Returns a reference to an existingFileSystem
.This method iterates over the
installed
providers to locate the provider that is identified by the URIscheme
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'sgetFileSystem
method is invoked to obtain a reference to theFileSystem
.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 throwsFileSystemNotFoundException
. 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 thenewFileSystem
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
- the URI to locate the file system- Returns:
- the reference to the file system
- Throws:
IllegalArgumentException
- if the pre-conditions for theuri
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 permission
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newFileSystem
Constructs a new file system that is identified by aURI
This method iterates over the
installed
providers to locate the provider that is identified by the URIscheme
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'snewFileSystem(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"));
- Parameters:
uri
- the URI identifying the file systemenv
- 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 theuri
parameter are not met, or theenv
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 implementation
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newFileSystem
public static FileSystem newFileSystem(URI uri, Map<String, ?> env, ClassLoader loader) throws IOExceptionConstructs a new file system that is identified by aURI
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 itsnewFileSystem(URI,Map)
is invoked to construct the new file system.- Parameters:
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 ornull
to only attempt to locate an installed provider- Returns:
- a new file system
- Throws:
IllegalArgumentException
- if the pre-conditions for theuri
parameter are not met, or theenv
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 implementation
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newFileSystem
Constructs a newFileSystem
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 aFileSystem
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.- Parameters:
path
- the path to the fileloader
- the class loader to locate the provider ornull
to only attempt to locate an installed provider- Returns:
- a new file system
- Throws:
ProviderNotFoundException
- 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
-
newFileSystem
Constructs a newFileSystem
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'snewFileSystem(Path, Map)
method is invoked to construct the new file system.- Parameters:
path
- the path to the fileenv
- a map of provider specific properties to configure the file system; may be empty- Returns:
- a new file system
- Throws:
ProviderNotFoundException
- 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- Since:
- 13
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newFileSystem
Constructs a newFileSystem
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'snewFileSystem(Path, Map)
method is invoked with an empty map to construct the new file system.- Parameters:
path
- the path to the file- Returns:
- a new file system
- Throws:
ProviderNotFoundException
- 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- Since:
- 13
-
newFileSystem
public static FileSystem newFileSystem(Path path, Map<String, ?> env, ClassLoader loader) throws IOExceptionConstructs a newFileSystem
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'snewFileSystem(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 aFileSystem
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.- Parameters:
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 ornull
to only attempt to locate an installed provider- Returns:
- a new file system
- Throws:
ProviderNotFoundException
- 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- Since:
- 13
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