/*
 * @(#)PolicySpi.java	1.2 05/11/17
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */


package java.security;

/**
 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
 * for the <code>Policy</code> 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</code>
 * object as an input parameter.  This constructor also must throw
 * an IllegalArgumentException if it does not understand the
 * <code>Policy.Parameters</code> input.
 *
 * @version 1.2, 11/17/05
 *
 * @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</code>
     * 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;
    }
}