Back to index...

	/*
	* Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.nio.file.attribute;

	import java.nio.ByteBuffer;
	import java.util.List;
	import java.io.IOException;

	/**
	* A file attribute view that provides a view of a file's user-defined
	* attributes, sometimes known as <em>extended attributes</em>. User-defined
	* file attributes are used to store metadata with a file that is not meaningful
	* to the file system. It is primarily intended for file system implementations
	* that support such a capability directly but may be emulated. The details of
	* such emulation are highly implementation specific and therefore not specified.
	*
	* <p> This {@code FileAttributeView} provides a view of a file's user-defined
	* attributes as a set of name/value pairs, where the attribute name is
	* represented by a {@code String}. An implementation may require to encode and
	* decode from the platform or file system representation when accessing the
	* attribute. The value has opaque content. This attribute view defines the
	* {@link #read read} and {@link #write write} methods to read the value into
	* or write from a {@link ByteBuffer}. This {@code FileAttributeView} is not
	* intended for use where the size of an attribute value is larger than {@link
	* Integer#MAX_VALUE}.
	*
	* <p> User-defined attributes may be used in some implementations to store
	* security related attributes so consequently, in the case of the default
	* provider at least, all methods that access user-defined attributes require the
	* {@code RuntimePermission("accessUserDefinedAttributes")} permission when a
	* security manager is installed.
	*
	* <p> The {@link java.nio.file.FileStore#supportsFileAttributeView
	* supportsFileAttributeView} method may be used to test if a specific {@link
	* java.nio.file.FileStore FileStore} supports the storage of user-defined
	* attributes.
	*
	* <p> Where dynamic access to file attributes is required, the {@link
	* java.nio.file.Files#getAttribute getAttribute} method may be used to read
	* the attribute value. The attribute value is returned as a byte array (byte[]).
	* The {@link java.nio.file.Files#setAttribute setAttribute} method may be used
	* to write the value of a user-defined attribute from a buffer (as if by
	* invoking the {@link #write write} method), or byte array (byte[]).
	*
	* @since 1.7
	*/

	public interface UserDefinedFileAttributeView
	extends FileAttributeView
	{
	/**
	* Returns the name of this attribute view. Attribute views of this type
	* have the name {@code "user"}.
	*/
	@Override
	String name();

	/**
	* Returns a list containing the names of the user-defined attributes.
	*
	* @return An unmodifiable list containing the names of the file's
	* user-defined
	*
	* @throws IOException
	* If an I/O error occurs
	* @throws SecurityException
	* In the case of the default provider, a security manager is
	* installed, and it denies {@link
	* RuntimePermission}<tt>("accessUserDefinedAttributes")</tt>
	* or its {@link SecurityManager#checkRead(String) checkRead} method
	* denies read access to the file.
	*/
	List<String> list() throws IOException;

	/**
	* Returns the size of the value of a user-defined attribute.
	*
	* @param name
	* The attribute name
	*
	* @return The size of the attribute value, in bytes.
	*
	* @throws ArithmeticException
	* If the size of the attribute is larger than {@link Integer#MAX_VALUE}
	* @throws IOException
	* If an I/O error occurs
	* @throws SecurityException
	* In the case of the default provider, a security manager is
	* installed, and it denies {@link
	* RuntimePermission}<tt>("accessUserDefinedAttributes")</tt>
	* or its {@link SecurityManager#checkRead(String) checkRead} method
	* denies read access to the file.
	*/
	int size(String name) throws IOException;

	/**
	* Read the value of a user-defined attribute into a buffer.
	*
	* <p> This method reads the value of the attribute into the given buffer
	* as a sequence of bytes, failing if the number of bytes remaining in
	* the buffer is insufficient to read the complete attribute value. The
	* number of bytes transferred into the buffer is {@code n}, where {@code n}
	* is the size of the attribute value. The first byte in the sequence is at
	* index {@code p} and the last byte is at index {@code p + n - 1}, where
	* {@code p} is the buffer's position. Upon return the buffer's position
	* will be equal to {@code p + n}; its limit will not have changed.
	*
	* <p> <b>Usage Example:</b>
	* Suppose we want to read a file's MIME type that is stored as a user-defined
	* attribute with the name "{@code user.mimetype}".
	* <pre>
	* UserDefinedFileAttributeView view =
	* Files.getFileAttributeView(path, UserDefinedFileAttributeView.class);
	* String name = "user.mimetype";
	* ByteBuffer buf = ByteBuffer.allocate(view.size(name));
	* view.read(name, buf);
	* buf.flip();
	* String value = Charset.defaultCharset().decode(buf).toString();
	* </pre>
	*
	* @param name
	* The attribute name
	* @param dst
	* The destination buffer
	*
	* @return The number of bytes read, possibly zero
	*
	* @throws IllegalArgumentException
	* If the destination buffer is read-only
	* @throws IOException
	* If an I/O error occurs or there is insufficient space in the
	* destination buffer for the attribute value
	* @throws SecurityException
	* In the case of the default provider, a security manager is
	* installed, and it denies {@link
	* RuntimePermission}<tt>("accessUserDefinedAttributes")</tt>
	* or its {@link SecurityManager#checkRead(String) checkRead} method
	* denies read access to the file.
	*
	* @see #size
	*/
	int read(String name, ByteBuffer dst) throws IOException;

	/**
	* Writes the value of a user-defined attribute from a buffer.
	*
	* <p> This method writes the value of the attribute from a given buffer as
	* a sequence of bytes. The size of the value to transfer is {@code r},
	* where {@code r} is the number of bytes remaining in the buffer, that is
	* {@code src.remaining()}. The sequence of bytes is transferred from the
	* buffer starting at index {@code p}, where {@code p} is the buffer's
	* position. Upon return, the buffer's position will be equal to {@code
	* p + n}, where {@code n} is the number of bytes transferred; its limit
	* will not have changed.
	*
	* <p> If an attribute of the given name already exists then its value is
	* replaced. If the attribute does not exist then it is created. If it
	* implementation specific if a test to check for the existence of the
	* attribute and the creation of attribute are atomic with respect to other
	* file system activities.
	*
	* <p> Where there is insufficient space to store the attribute, or the
	* attribute name or value exceed an implementation specific maximum size
	* then an {@code IOException} is thrown.
	*
	* <p> <b>Usage Example:</b>
	* Suppose we want to write a file's MIME type as a user-defined attribute:
	* <pre>
	* UserDefinedFileAttributeView view =
	* FIles.getFileAttributeView(path, UserDefinedFileAttributeView.class);
	* view.write("user.mimetype", Charset.defaultCharset().encode("text/html"));
	* </pre>
	*
	* @param name
	* The attribute name
	* @param src
	* The buffer containing the attribute value
	*
	* @return The number of bytes written, possibly zero
	*
	* @throws IOException
	* If an I/O error occurs
	* @throws SecurityException
	* In the case of the default provider, a security manager is
	* installed, and it denies {@link
	* RuntimePermission}<tt>("accessUserDefinedAttributes")</tt>
	* or its {@link SecurityManager#checkWrite(String) checkWrite}
	* method denies write access to the file.
	*/
	int write(String name, ByteBuffer src) throws IOException;

	/**
	* Deletes a user-defined attribute.
	*
	* @param name
	* The attribute name
	*
	* @throws IOException
	* If an I/O error occurs or the attribute does not exist
	* @throws SecurityException
	* In the case of the default provider, a security manager is
	* installed, and it denies {@link
	* RuntimePermission}<tt>("accessUserDefinedAttributes")</tt>
	* or its {@link SecurityManager#checkWrite(String) checkWrite}
	* method denies write access to the file.
	*/
	void delete(String name) throws IOException;
	}

Back to index...