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   * Copyright (c) 2005, 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
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   */
  
  
  package java.security;
  
  /**
   * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
   * for the {@code Policy} class.
   * All the abstract methods in this class must be implemented by each
   * service provider who wishes to supply a Policy implementation.
   *
   * <p> Subclass implementations of this abstract class must provide
   * a public constructor that takes a {@code Policy.Parameters}
   * object as an input parameter.  This constructor also must throw
   * an IllegalArgumentException if it does not understand the
   * {@code Policy.Parameters} input.
   *
   *
   * @since 1.6
   */
  
  public abstract class PolicySpi {
  
      /**
       * Check whether the policy has granted a Permission to a ProtectionDomain.
       *
       * @param domain the ProtectionDomain to check.
       *
       * @param permission check whether this permission is granted to the
       *          specified domain.
       *
       * @return boolean true if the permission is granted to the domain.
       */
      protected abstract boolean engineImplies
          (ProtectionDomain domain, Permission permission);
  
      /**
       * Refreshes/reloads the policy configuration. The behavior of this method
       * depends on the implementation. For example, calling {@code refresh}
       * on a file-based policy will cause the file to be re-read.
       *
       * <p> The default implementation of this method does nothing.
       * This method should be overridden if a refresh operation is supported
       * by the policy implementation.
       */
      protected void engineRefresh() { }
  
      /**
       * Return a PermissionCollection object containing the set of
       * permissions granted to the specified CodeSource.
       *
       * <p> The default implementation of this method returns
       * Policy.UNSUPPORTED_EMPTY_COLLECTION object.  This method can be
       * overridden if the policy implementation can return a set of
       * permissions granted to a CodeSource.
       *
       * @param codesource the CodeSource to which the returned
       *          PermissionCollection has been granted.
       *
       * @return a set of permissions granted to the specified CodeSource.
       *          If this operation is supported, the returned
       *          set of permissions must be a new mutable instance
       *          and it must support heterogeneous Permission types.
       *          If this operation is not supported,
       *          Policy.UNSUPPORTED_EMPTY_COLLECTION is returned.
       */
      protected PermissionCollection engineGetPermissions
                                          (CodeSource codesource) {
          return Policy.UNSUPPORTED_EMPTY_COLLECTION;
      }
  
      /**
       * Return a PermissionCollection object containing the set of
       * permissions granted to the specified ProtectionDomain.
       *
       * <p> The default implementation of this method returns
       * Policy.UNSUPPORTED_EMPTY_COLLECTION object.  This method can be
       * overridden if the policy implementation can return a set of
       * permissions granted to a ProtectionDomain.
       *
       * @param domain the ProtectionDomain to which the returned
       *          PermissionCollection has been granted.
       *
       * @return a set of permissions granted to the specified ProtectionDomain.
       *          If this operation is supported, the returned
       *          set of permissions must be a new mutable instance
       *          and it must support heterogeneous Permission types.
       *          If this operation is not supported,
       *          Policy.UNSUPPORTED_EMPTY_COLLECTION is returned.
       */
      protected PermissionCollection engineGetPermissions
                                          (ProtectionDomain domain) {
          return Policy.UNSUPPORTED_EMPTY_COLLECTION;
      }
  }
  