standardcombiningalgfactory.java

来自「sunxacml源码」· Java 代码 · 共 214 行

/*
 * @(#)StandardCombiningAlgFactory.java
 *
 * Copyright 2004-2006 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
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 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution in binary form must reproduce the above copyright
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 *      documentation and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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package com.sun.xacml.combine;

import com.sun.xacml.PolicyMetaData;
import com.sun.xacml.UnknownIdentifierException;

import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import java.util.logging.Level;
import java.util.logging.Logger;


/**
 * This factory supports the standard set of algorithms specified in XACML
 * 1.x and 2.0. It is the default factory used by the system, and imposes
 * a singleton pattern insuring that there is only ever one instance of
 * this class.
 * <p>
 * Note that because this supports only the standard algorithms, this
 * factory does not allow the addition of any other algorithms. If you call
 * <code>addAlgorithm</code> on an instance of this class, an exception
 * will be thrown. If you need a standard factory that is modifiable, you
 * should create a new <code>BaseCombiningAlgFactory</code> (or some other
 * <code>CombiningAlgFactory</code>) and configure it with the standard
 * algorithms using <code>getStandardAlgorithms</code> (or, in the case of
 * <code>BaseAttributeFactory</code>, by providing the datatypes in the
 * constructor).
 *
 * @since 1.2
 * @author Seth Proctor
 */
public class StandardCombiningAlgFactory extends BaseCombiningAlgFactory
{

    // the single factory instance
    private static StandardCombiningAlgFactory factoryInstance = null;

    // the algorithms supported by this factory
    private static Set supportedAlgorithms = null;

    // identifiers for the supported algorithms
    private static Set supportedAlgIds;

    // the logger we'll use for all messages
    private static final Logger logger =
        Logger.getLogger(StandardCombiningAlgFactory.class.getName());

    /**
     * Default constructor.
     */
    private StandardCombiningAlgFactory() {
        super(supportedAlgorithms);
    }

    /**
     * Private initializer for the supported algorithms. This isn't called
     * until something needs these values, and is only called once.
     */
    private static void initAlgorithms() {
        logger.config("Initializing standard combining algorithms");

        supportedAlgorithms = new HashSet();
        supportedAlgIds = new HashSet();
        
        supportedAlgorithms.add(new DenyOverridesRuleAlg());
        supportedAlgIds.add(DenyOverridesRuleAlg.algId);
        supportedAlgorithms.add(new DenyOverridesPolicyAlg());
        supportedAlgIds.add(DenyOverridesPolicyAlg.algId);

        supportedAlgorithms.add(new OrderedDenyOverridesRuleAlg());
        supportedAlgIds.add(OrderedDenyOverridesRuleAlg.algId);
        supportedAlgorithms.add(new OrderedDenyOverridesPolicyAlg());
        supportedAlgIds.add(OrderedDenyOverridesPolicyAlg.algId);
        
        supportedAlgorithms.add(new PermitOverridesRuleAlg());
        supportedAlgIds.add(PermitOverridesRuleAlg.algId);
        supportedAlgorithms.add(new PermitOverridesPolicyAlg());
        supportedAlgIds.add(PermitOverridesPolicyAlg.algId);
        
        supportedAlgorithms.add(new OrderedPermitOverridesRuleAlg());
        supportedAlgIds.add(OrderedPermitOverridesRuleAlg.algId);
        supportedAlgorithms.add(new OrderedPermitOverridesPolicyAlg());
        supportedAlgIds.add(OrderedPermitOverridesPolicyAlg.algId);
        
        supportedAlgorithms.add(new FirstApplicableRuleAlg());
        supportedAlgIds.add(FirstApplicableRuleAlg.algId);
        supportedAlgorithms.add(new FirstApplicablePolicyAlg());
        supportedAlgIds.add(FirstApplicablePolicyAlg.algId);
        
        supportedAlgorithms.add(new OnlyOneApplicablePolicyAlg());
        supportedAlgIds.add(OnlyOneApplicablePolicyAlg.algId);

        supportedAlgIds = Collections.unmodifiableSet(supportedAlgIds);
    }

    /**
     * Returns an instance of this factory. This method enforces a singleton
     * model, meaning that this always returns the same instance, creating
     * the factory if it hasn't been requested before. This is the default
     * model used by the <code>CombiningAlgFactory</code>, ensuring quick
     * access to this factory.
     *
     * @return the factory instance
     */
    public static StandardCombiningAlgFactory getFactory() {
        if (factoryInstance == null) {
            synchronized (StandardCombiningAlgFactory.class) {
                if (factoryInstance == null) {
                    initAlgorithms();
                    factoryInstance = new StandardCombiningAlgFactory();
                }
            }
        }
        
        return factoryInstance;
    }

    /**
     * A convenience method that returns a new instance of a
     * <code>CombiningAlgFactory</code> that supports all of the standard
     * algorithms. The new factory allows adding support for new algorithms.
     * This method should only be used when you need a new, mutable instance
     * (eg, when you want to create a new factory that extends the set of
     * supported algorithms). In general, you should use
     * <code>getFactory</code> which is more efficient and enforces a
     * singleton pattern.
     *
     * @return a new factory supporting the standard algorithms
     */
    public static CombiningAlgFactory getNewFactory() {
        // first we make sure everything's been initialized...
        getFactory();

        // ...then we create the new instance
        return new BaseCombiningAlgFactory(supportedAlgorithms);
    }

    /**
     * Returns the identifiers supported for the given version of XACML.
     * Because this factory supports identifiers from all versions of the
     * XACML specifications, this method is useful for getting a list of
     * which specific identifiers are supported by a given version of XACML.
     *
     * @param xacmlVersion a standard XACML identifier string, as provided
     *                     in <code>PolicyMetaData</code>
     *
     * @return a <code>Set</code> of identifiers
     *
     * @throws UnknownIdentifierException if the version string is unknown
     */
    public static Set getStandardAlgorithms(String xacmlVersion)
        throws UnknownIdentifierException
    {
        if ((xacmlVersion.equals(PolicyMetaData.XACML_1_0_IDENTIFIER)) ||
            (xacmlVersion.equals(PolicyMetaData.XACML_2_0_IDENTIFIER)))
            return supportedAlgIds;

        throw new UnknownIdentifierException("Unknown XACML version: " +
                                             xacmlVersion);
    }

    /**
     * Throws an <code>UnsupportedOperationException</code> since you are not
     * allowed to modify what a standard factory supports.
     *
     * @param alg the combining algorithm to add
     *
     * @throws UnsupportedOperationException always
     */
    public void addAlgorithm(CombiningAlgorithm alg) {
        throw new UnsupportedOperationException("a standard factory cannot " +
                                                "support new algorithms");
    }

}