function.java

sunxacml源码

/*
 * @(#)Function.java
 *
 * Copyright 2003-2005 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:
 *
 *   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
 *      notice, this list of conditions and the following disclaimer in the
 *      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
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
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 *
 * You acknowledge that this software is not designed or intended for use in
 * the design, construction, operation or maintenance of any nuclear facility.
 */

package com.sun.xacml.cond;

import com.sun.xacml.EvaluationCtx;
import com.sun.xacml.Indenter;

import com.sun.xacml.attr.AttributeValue;

import java.net.URI;

import java.io.OutputStream;

import java.util.List;


/**
 * Interface that all functions in the system must implement.
 *
 * @since 1.0
 * @author Seth Proctor
 */
public interface Function extends Expression
{

    /**
     * Evaluates the <code>Function</code> using the given inputs.
     * The <code>List</code> contains <code>Evaluatable<code>s which are all
     * of the correct type if the <code>Function</code> has been created as
     * part of an <code>Apply</code> or <code>TargetMatch</code>, but which
     * may otherwise be invalid. Each parameter should be evaluated by the
     * <code>Function</code>, unless the <code>Function</code>
     * doesn't need to evaluate all inputs to determine a result (as in the
     * case of the or function). The order of the <code>List</code> is
     * significant, so a <code>Function</code> should have a very good reason
     * if it wants to evaluate the inputs in a different order.
     * <p>
     * Note that if this is a higher-order function, like any-of, then
     * some argument (typically the first) in the <code>List</code> will
     * actually be a Function object representing the function to apply to
     * some bag. A function needs to know if it's a higher-order function,
     * and therefore whether or not to look for this case. Also, a
     * higher-order function is responsible for checking that the inputs
     * that it will pass to the <code>Function</code> provided as the first
     * parameter are valid, ie. it must do a <code>checkInputs</code> on
     * its sub-function when <code>checkInputs</code> is called on the
     * higher-order function.
     *
     * @param inputs the <code>List</code> of inputs for the function
     * @param context the representation of the request
     *
     * @return a result containing the <code>AttributeValue</code> computed
     *         when evaluating the function, or <code>Status</code>
     *         specifying some error condition
     */
    public EvaluationResult evaluate(List inputs, EvaluationCtx context);

    /**
     * Returns the identifier of this function as known by the factories.
     * In the case of the standard XACML functions, this will be one of the
     * URIs defined in the standard namespace. This function must always
     * return the complete namespace and identifier of this function.
     *
     * @return the function's identifier
     */
    public URI getIdentifier();

    /**
     * Provides the type of <code>AttributeValue</code> that this function
     * returns from <code>evaluate</code> in a successful evaluation.
     *
     * @return the type returned by this function
     */
    public URI getReturnType();

    /**
     * Tells whether this function will return a bag of values or just a
     * single value.
     *
     * @return true if evaluation will return a bag, false otherwise
     */
    public boolean returnsBag();

    /**
     * Checks that the given inputs are of the right types, in the right
     * order, and are the right number for this function to evaluate. If
     * the function cannot accept the inputs for evaluation, an
     * <code>IllegalArgumentException</code> is thrown.
     *
     * @param inputs a <code>List</code> of <code>Evaluatable</code>s, with
     *               the first argument being a <code>Function</code> if
     *               this is a higher-order function
     *
     * @throws IllegalArgumentException if the inputs do match what the
     *                                  function accepts for evaluation
     */
    public void checkInputs(List inputs) throws IllegalArgumentException;

    /**
     * Checks that the given inputs are of the right types, in the right
     * order, and are the right number for this function to evaluate. If
     * the function cannot accept the inputs for evaluation, an
     * <code>IllegalArgumentException</code> is thrown. Unlike the other
     * <code>checkInput</code> method in this interface, this assumes that
     * the parameters will never provide bags of values. This is useful if
     * you're considering a target function which has a designator or
     * selector in its input list, but which passes the values from the
     * derived bags one at a time to the function, so the function doesn't
     * have to deal with the bags that the selector or designator
     * generates.
     *
     * @param inputs a <code>List</code> of <code>Evaluatable</code>s, with
     *               the first argument being a <code>Function</code> if
     *               this is a higher-order function
     *
     * @throws IllegalArgumentException if the inputs do match what the
     *                                  function accepts for evaluation
     */
    public void checkInputsNoBag(List inputs) throws IllegalArgumentException;
 
    /**
     * Encodes this <code>Function</code> into its XML representation and
     * writes this encoding to the given <code>OutputStream</code> with no
     * indentation.
     *
     * @param output a stream into which the XML-encoded data is written
     */
    public void encode(OutputStream output);

    /**
     * Encodes this <code>Function</code> into its XML representation and
     * writes this encoding to the given <code>OutputStream</code> with
     * indentation.
     *
     * @param output a stream into which the XML-encoded data is written
     * @param indenter an object that creates indentation strings
     */
    public void encode(OutputStream output, Indenter indenter);
   
}