/* Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.security.access;

import java.io.Serializable;

import org.springframework.security.access.intercept.RunAsManager;


/**
 * Stores a security system related configuration attribute.
 *
 * <p>
 * When an {@link org.springframework.security.access.intercept.AbstractSecurityInterceptor}
 * is set up, a list of configuration attributes is defined for secure object
 * patterns. These configuration attributes have special meaning to a {@link RunAsManager},
 * {@link AccessDecisionManager} or <code>AccessDecisionManager</code> delegate.
 *
 * <p>
 * Stored at runtime with other <code>ConfigAttribute</code>s for the same secure object target.
 *
 * @author Ben Alex
 */
public interface ConfigAttribute extends Serializable {
    //~ Methods ========================================================================================================

    /**
     * If the <code>ConfigAttribute</code> can be represented as a <code>String</code> and that
     * <code>String</code> is sufficient in precision to be relied upon as a configuration parameter by a {@link
     * RunAsManager}, {@link AccessDecisionManager} or <code>AccessDecisionManager</code> delegate, this method should
     * return such a <code>String</code>.
     * <p>
     * If the <code>ConfigAttribute</code> cannot be expressed with sufficient precision as a <code>String</code>,
     * <code>null</code> should be returned. Returning <code>null</code> will require any relying classes to
     * specifically support the <code>ConfigAttribute</code> implementation, so returning <code>null</code> should
     * be avoided unless actually required.
     *
     * @return a representation of the configuration attribute (or <code>null</code> if the configuration attribute
     *         cannot be expressed as a <code>String</code> with sufficient precision).
     */
    String getAttribute();
}
