Expression.java

/*
 * @(#)Expression.java
 *
 * Copyright 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
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package com.sun.xacml.cond;

import com.sun.xacml.Indenter;
import com.sun.xacml.debug.Locatable;

import java.net.URI;
import java.util.Collections;
import java.util.List;

import java.io.OutputStream;
import java.io.UnsupportedEncodingException;


/**
 * This interface represents the expression type in the XACML 2.0 schema.
 *
 * @since 2.0
 * @author Seth Proctor
 */
public interface Expression extends Locatable
{
	public static List<Expression> EMPTY_LIST = Collections.<Expression>emptyList();

    /**
     * Returns the type of the expression. This may be the data type of
     * an <code>AttributeValue</code>, the return type of a
     * <code>Function</code>, etc.
     *
     * @return the attribute type of the referenced expression
     */
    public URI getType();

    /**
     * Returns whether or not this expression returns, or evaluates to a
     * Bag. Note that <code>Evaluatable</code>, which extends this interface,
     * defines <code>evaluatesToBag</code> which is essentially the same
     * function. This method has been deprecated, and <code>returnsBag</code>
     * is now the preferred way to query all <code>Expression</code>s.
     * 
     * @return  true or false.
     */
    public boolean returnsBag();

    /**
     * Encodes this <code>Expression</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
     * @param charsetName  the character set to use in encoding of strings.
     *                     This may be null in which case the platform
     *                     default character set will be used.
     */
    public void encode(OutputStream output, String charsetName)
        throws UnsupportedEncodingException;

    /**
     * Encodes this <code>Expression</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 charsetName  the character set to use in encoding of strings.
     *                     This may be null in which case the platform
     *                     default character set will be used.
     * @param indenter an object that creates indentation strings
     */
    public void encode(OutputStream output, String charsetName,
                       Indenter indenter)
        throws UnsupportedEncodingException;

}