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package java.nio.file.attribute;

import java.nio.file.*;
import java.util.List;
import java.io.IOException;


A file attribute view that supports reading or updating a file's Access
Control Lists (ACL) or file owner attributes.

 ACLs are used to specify access rights to file system objects. An ACL is an ordered list of access-control-entries, each specifying a UserPrincipal and the level of access for that user principal. This file attribute view defines the getAcl, and setAcl methods to read and write ACLs based on the ACL model specified in RFC 3530:
Network File System (NFS) version 4 Protocol. This file attribute view
is intended for file system implementations that support the NFSv4 ACL model
or have a well-defined mapping between the NFSv4 ACL model and the ACL
model used by the file system. The details of such mapping are implementation
dependent and are therefore unspecified.

 This class also extends FileOwnerAttributeView so as to define methods to get and set the file owner. 
 When a file system provides access to a set of 
file-systems that are not homogeneous then only some of the file systems may support ACLs. The 
supportsFileAttributeView method can be used to test if a file system supports ACLs. 
Interoperability
 RFC 3530 allows for special user identities to be used on platforms that support the POSIX defined access permissions. The special user identities are "OWNER@", "GROUP@", and "EVERYONE@". When both the AclFileAttributeView and the PosixFileAttributeView are supported then these special user identities may be included in ACL entries that are read or written. The file system's UserPrincipalLookupService may be used to obtain a UserPrincipal to represent these special identities by invoking the lookupPrincipalByName method. 
 Usage Example:
Suppose we wish to add an entry to an existing ACL to grant "joe" access:

    // lookup "joe"
    UserPrincipal joe = file.getFileSystem().getUserPrincipalLookupService()
        .lookupPrincipalByName("joe");
    // get view
    AclFileAttributeView view = Files.getFileAttributeView(file, AclFileAttributeView.class);
    // create ACE to give "joe" read access
    AclEntry entry = AclEntry.newBuilder()
        .setType(AclEntryType.ALLOW)
        .setPrincipal(joe)
        .setPermissions(AclEntryPermission.READ_DATA, AclEntryPermission.READ_ATTRIBUTES)
        .build();
    // read ACL, insert ACE, re-write ACL
    List<AclEntry> acl = view.getAcl();
    acl.add(0, entry);   // insert before any DENY entries
    view.setAcl(acl);



 Dynamic Access 


 Where dynamic access to file attributes is required, the attributes
supported by this attribute view are as follows:




Supported attributes

  

     Name 
     Type 
  



  

     "acl" 
     List<AclEntry> 
  

  

     "owner" 
     UserPrincipal 
  







 The getAttribute method may be used to read the ACL or owner attributes as if by invoking the getAcl or getOwner methods. 
 The setAttribute method may be used to update the ACL or owner attributes as if by invoking the setAcl or setOwner methods. 
 Setting the ACL when creating a file 


 Implementations supporting this attribute view may also support setting the initial ACL when creating a file or directory. The initial ACL may be provided to methods such as createFile or createDirectory as an FileAttribute with name "acl:acl" and a 
value that is the list of AclEntry objects. 
 Where an implementation supports an ACL model that differs from the NFSv4 defined ACL model then setting the initial ACL when creating the file must translate the ACL to the model supported by the file system. Methods that create a file should reject (by throwing IOException) any attempt to create a file that would be less secure as a result of the translation. 
Since:1.7
/**
 * A file attribute view that supports reading or updating a file's Access
 * Control Lists (ACL) or file owner attributes.
 *
 * <p> ACLs are used to specify access rights to file system objects. An ACL is
 * an ordered list of {@link AclEntry access-control-entries}, each specifying a
 * {@link UserPrincipal} and the level of access for that user principal. This
 * file attribute view defines the {@link #getAcl() getAcl}, and {@link
 * #setAcl(List) setAcl} methods to read and write ACLs based on the ACL
 * model specified in <a href="http://www.ietf.org/rfc/rfc3530.txt"><i>RFC&nbsp;3530:
 * Network File System (NFS) version 4 Protocol</i></a>. This file attribute view
 * is intended for file system implementations that support the NFSv4 ACL model
 * or have a <em>well-defined</em> mapping between the NFSv4 ACL model and the ACL
 * model used by the file system. The details of such mapping are implementation
 * dependent and are therefore unspecified.
 *
 * <p> This class also extends {@code FileOwnerAttributeView} so as to define
 * methods to get and set the file owner.
 *
 * <p> When a file system provides access to a set of {@link FileStore
 * file-systems} that are not homogeneous then only some of the file systems may
 * support ACLs. The {@link FileStore#supportsFileAttributeView
 * supportsFileAttributeView} method can be used to test if a file system
 * supports ACLs.
 *
 * <h2>Interoperability</h2>
 *
 * RFC&nbsp;3530 allows for special user identities to be used on platforms that
 * support the POSIX defined access permissions. The special user identities
 * are "{@code OWNER@}", "{@code GROUP@}", and "{@code EVERYONE@}". When both
 * the {@code AclFileAttributeView} and the {@link PosixFileAttributeView}
 * are supported then these special user identities may be included in ACL {@link
 * AclEntry entries} that are read or written. The file system's {@link
 * UserPrincipalLookupService} may be used to obtain a {@link UserPrincipal}
 * to represent these special identities by invoking the {@link
 * UserPrincipalLookupService#lookupPrincipalByName lookupPrincipalByName}
 * method.
 *
 * <p> <b>Usage Example:</b>
 * Suppose we wish to add an entry to an existing ACL to grant "joe" access:
 * <pre>
 *     // lookup "joe"
 *     UserPrincipal joe = file.getFileSystem().getUserPrincipalLookupService()
 *         .lookupPrincipalByName("joe");
 *
 *     // get view
 *     AclFileAttributeView view = Files.getFileAttributeView(file, AclFileAttributeView.class);
 *
 *     // create ACE to give "joe" read access
 *     AclEntry entry = AclEntry.newBuilder()
 *         .setType(AclEntryType.ALLOW)
 *         .setPrincipal(joe)
 *         .setPermissions(AclEntryPermission.READ_DATA, AclEntryPermission.READ_ATTRIBUTES)
 *         .build();
 *
 *     // read ACL, insert ACE, re-write ACL
 *     List&lt;AclEntry&gt; acl = view.getAcl();
 *     acl.add(0, entry);   // insert before any DENY entries
 *     view.setAcl(acl);
 * </pre>
 *
 * <h2> Dynamic Access </h2>
 * <p> Where dynamic access to file attributes is required, the attributes
 * supported by this attribute view are as follows:
 * <blockquote>
 * <table class="striped">
 * <caption style="display:none">Supported attributes</caption>
 * <thead>
 *   <tr>
 *     <th scope="col"> Name </th>
 *     <th scope="col"> Type </th>
 *   </tr>
 * </thead>
 * <tbody>
 *   <tr>
 *     <th scope="row"> "acl" </th>
 *     <td> {@link List}&lt;{@link AclEntry}&gt; </td>
 *   </tr>
 *   <tr>
 *     <th scope="row"> "owner" </th>
 *     <td> {@link UserPrincipal} </td>
 *   </tr>
 * </tbody>
 * </table>
 * </blockquote>
 *
 * <p> The {@link Files#getAttribute getAttribute} method may be used to read
 * the ACL or owner attributes as if by invoking the {@link #getAcl getAcl} or
 * {@link #getOwner getOwner} methods.
 *
 * <p> The {@link Files#setAttribute setAttribute} method may be used to
 * update the ACL or owner attributes as if by invoking the {@link #setAcl setAcl}
 * or {@link #setOwner setOwner} methods.
 *
 * <h2> Setting the ACL when creating a file </h2>
 *
 * <p> Implementations supporting this attribute view may also support setting
 * the initial ACL when creating a file or directory. The initial ACL
 * may be provided to methods such as {@link Files#createFile createFile} or {@link
 * Files#createDirectory createDirectory} as an {@link FileAttribute} with {@link
 * FileAttribute#name name} {@code "acl:acl"} and a {@link FileAttribute#value
 * value} that is the list of {@code AclEntry} objects.
 *
 * <p> Where an implementation supports an ACL model that differs from the NFSv4
 * defined ACL model then setting the initial ACL when creating the file must
 * translate the ACL to the model supported by the file system. Methods that
 * create a file should reject (by throwing {@link IOException IOException})
 * any attempt to create a file that would be less secure as a result of the
 * translation.
 *
 * @since 1.7
 */

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

    
Reads the access control list.

 When the file system uses an ACL model that differs from the NFSv4
defined ACL model, then this method returns an ACL that is the translation
of the ACL to the NFSv4 ACL model.

 The returned list is modifiable so as to facilitate changes to the existing ACL. The setAcl method is used to update the file's ACL attribute. 
Throws:
Returns: an ordered list of entries representing the ACL
/**
     * Reads the access control list.
     *
     * <p> When the file system uses an ACL model that differs from the NFSv4
     * defined ACL model, then this method returns an ACL that is the translation
     * of the ACL to the NFSv4 ACL model.
     *
     * <p> The returned list is modifiable so as to facilitate changes to the
     * existing ACL. The {@link #setAcl setAcl} method is used to update
     * the file's ACL attribute.
     *
     * @return  an ordered list of {@link AclEntry entries} representing the
     *          ACL
     *
     * @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}{@code ("accessUserInformation")}
     *          or its {@link SecurityManager#checkRead(String) checkRead} method
     *          denies read access to the file.
     */
    List<AclEntry> getAcl() throws IOException;

    
Updates (replace) the access control list.

 Where the file system supports Access Control Lists, and it uses an ACL model that differs from the NFSv4 defined ACL model, then this method must translate the ACL to the model supported by the file system. This method should reject (by throwing IOException) any attempt to write an ACL that would appear to make the file more secure than would be the case if the ACL were updated. Where an implementation does not support a mapping of AclEntryType.AUDIT or AclEntryType.ALARM entries, then this method ignores these entries when writing the ACL. 
 If an ACL entry contains a user-principal that is not associated with the same provider as this attribute view then ProviderMismatchException is thrown. Additional validation, if any, is implementation dependent. 
 If the file system supports other security related file attributes (such as a file 
access-permissions for example), the updating the access control list may also cause these security related attributes to be updated. 
Params:
  • acl – 
         the new access control list
Throws:
/**
     * Updates (replace) the access control list.
     *
     * <p> Where the file system supports Access Control Lists, and it uses an
     * ACL model that differs from the NFSv4 defined ACL model, then this method
     * must translate the ACL to the model supported by the file system. This
     * method should reject (by throwing {@link IOException IOException}) any
     * attempt to write an ACL that would appear to make the file more secure
     * than would be the case if the ACL were updated. Where an implementation
     * does not support a mapping of {@link AclEntryType#AUDIT} or {@link
     * AclEntryType#ALARM} entries, then this method ignores these entries when
     * writing the ACL.
     *
     * <p> If an ACL entry contains a {@link AclEntry#principal user-principal}
     * that is not associated with the same provider as this attribute view then
     * {@link ProviderMismatchException} is thrown. Additional validation, if
     * any, is implementation dependent.
     *
     * <p> If the file system supports other security related file attributes
     * (such as a file {@link PosixFileAttributes#permissions
     * access-permissions} for example), the updating the access control list
     * may also cause these security related attributes to be updated.
     *
     * @param   acl
     *          the new access control list
     *
     * @throws  IOException
     *          if an I/O error occurs or the ACL is invalid
     * @throws  SecurityException
     *          In the case of the default provider, a security manager is
     *          installed, it denies {@link RuntimePermission}{@code ("accessUserInformation")}
     *          or its {@link SecurityManager#checkWrite(String) checkWrite}
     *          method denies write access to the file.
     */
    void setAcl(List<AclEntry> acl) throws IOException;
}