Package org.apache.beam.sdk.io.fs

Interface ResourceId

All Superinterfaces:

Serializable

All Known Implementing Classes:

ClassLoaderFileSystem.ClassLoaderResourceId, GcsResourceId

public interface ResourceId
extends Serializable

An identifier which represents a file-like resource.

ResourceId is hierarchical and composed of a sequence of directory and file name elements separated by a special separator or delimiter.

ResourceIds are created using FileSystems. The two primary mechanisms are:

• FileSystems.match(java.util.List), which takes a list of String resource names or globs, queries the FileSystem for resources matching these specifications, and returns a MatchResult for each glob. This is typically used when reading from files.
• FileSystems.matchNewResource(String, boolean), which takes a String full resource name and type (file or directory) and generates a FileSystem-specific ResourceId for that resource. This call does not verify the presence or absence of that resource in the file system. This call is typically used when creating new directories or files to generate ResourceIds for resources that may not yet exist.

Method Summary

Modifier and Type	Method	Description
ResourceId	getCurrentDirectory()	Returns the ResourceId that represents the current directory of this ResourceId.
@Nullable String	getFilename()	Returns the name of the file or directory denoted by this ResourceId.
String	getScheme()	Get the scheme which defines the namespace of the ResourceId.
boolean	isDirectory()	Returns true if this ResourceId represents a directory, false otherwise.
ResourceId	resolve(String other, ResolveOptions resolveOptions)	Returns a child ResourceId under this.
String	toString()	Returns the string representation of this ResourceId.

Method Details

resolve

ResourceId resolve(String other,
 ResolveOptions resolveOptions)

Returns a child ResourceId under this.

In order to write file system agnostic code, callers should not include delimiters in other, and should use ResolveOptions.StandardResolveOptions to specify whether to resolve a file or a directory.

For example:

 ResourceId homeDir = ...;
 ResourceId tempOutput = homeDir
     .resolve("tempDir", StandardResolveOptions.RESOLVE_DIRECTORY)
     .resolve("output", StandardResolveOptions.RESOLVE_FILE);
 

This ResourceId should represents a directory.

It is up to each file system to resolve in their own way.

Resolving special characters:

• resourceId.resolve("..", StandardResolveOptions.RESOLVE_DIRECTORY) returns the parent directory of this ResourceId.
• resourceId.resolve("*", StandardResolveOptions.RESOLVE_FILE) returns a ResourceId which matches all files in this ResourceId.
• resourceId.resolve("*", StandardResolveOptions.RESOLVE_DIRECTORY) returns a ResourceId which matches all directories in this ResourceId.

Throws:

IllegalStateException - if this ResourceId is not a directory.

IllegalArgumentException - if other contains illegal characters or is an illegal name. It is recommended that callers use common characters, such as [_a-zA-Z0-9.-], in other.

getCurrentDirectory

ResourceId getCurrentDirectory()

Returns the ResourceId that represents the current directory of this ResourceId.

If it is already a directory, trivially returns this.

getScheme

String getScheme()

Get the scheme which defines the namespace of the ResourceId.

The scheme is required to follow URI scheme syntax. See RFC 2396

getFilename

@Nullable String getFilename()

Returns the name of the file or directory denoted by this ResourceId. The file name is the farthest element from the root in the directory hierarchy.

Returns:

a string representing the name of file or directory, or null if there are zero components.

isDirectory

boolean isDirectory()

Returns true if this ResourceId represents a directory, false otherwise.

toString

String toString()

Returns the string representation of this ResourceId.

The corresponding FileSystem.match(java.util.List<java.lang.String>) is required to accept this string representation.

Overrides:

toString in class Object