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| 1 | /* | |
| 2 | * Copyright (c) 2000-2005, University of Salford | |
| 3 | * All rights reserved. | |
| 4 | * | |
| 5 | * Redistribution and use in source and binary forms, with or without | |
| 6 | * modification, are permitted provided that the following conditions are met: | |
| 7 | * | |
| 8 | * Redistributions of source code must retain the above copyright notice, this | |
| 9 | * list of conditions and the following disclaimer. | |
| 10 | * | |
| 11 | * Redistributions in binary form must reproduce the above copyright notice, | |
| 12 | * this list of conditions and the following disclaimer in the documentation | |
| 13 | * and/or other materials provided with the distribution. | |
| 14 | * | |
| 15 | * Neither the name of the University of Salford nor the names of its | |
| 16 | * contributors may be used to endorse or promote products derived from this | |
| 17 | * software without specific prior written permission. | |
| 18 | * | |
| 19 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | |
| 20 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 21 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
| 22 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE | |
| 23 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
| 24 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF | |
| 25 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS | |
| 26 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN | |
| 27 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |
| 28 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |
| 29 | * POSSIBILITY OF SUCH DAMAGE. | |
| 30 | */ | |
| 31 | ||
| 32 | package issrg.pba.rbac.xmlpolicy.ifstatement; | |
| 33 | ||
| 34 | /** | |
| 35 | * This is an abstract class which is a base to other operations. The | |
| 36 | * sub-classes would only | |
| 37 | * need to have a valid constructor, so the XMLParser will be able to | |
| 38 | * instantiate a working | |
| 39 | * copy of it, and perhaps a static registration method to update the collection | |
| 40 | * of interpreters. | |
| 41 | * | |
| 42 | * <p>This class maintains a registry of Interpreters for each type of | |
| 43 | * operation. During evaluation time an Interpreter will be found in the | |
| 44 | * registry for the | |
| 45 | * required type of operation and it will be used to perform the evaluation. | |
| 46 | * If no Interpreter can be found for the specific set of Terms, | |
| 47 | * EvaluationException occurs. | |
| 48 | * | |
| 49 | * @see Interpreter | |
| 50 | */ | |
| 51 | public class OperationNode extends TermNode { | |
| 52 | protected String type; | |
| 53 | protected Interpreter interpreter; | |
| 54 | ||
| 55 | 0 |
 protected OperationNode() {} |
| 56 | ||
| 57 | /** | |
| 58 | * This constructor builds an OperationNode given the name and the attributes | |
| 59 | * of the XML element, and the acceptable numbers of operands. | |
| 60 | * | |
| 61 | * @param nodeName - the name of the XML element this OperationNode represents | |
| 62 | * @param attrs - the attributes of this XML element | |
| 63 | * @param maxOperandCount - the maximum acceptable number of operands; if | |
| 64 | * "-1", any number of operands is acceptable | |
| 65 | * @param minOperandCount - the minimum acceptable number of operands | |
| 66 | */ | |
| 67 | 144 |
public OperationNode(String nodeName, org.xml.sax.Attributes attrs, int maxOperandCount, int minOperandCount){ |
| 68 | 144 | super(nodeName, attrs, maxOperandCount, minOperandCount); |
| 69 | } | |
| 70 | ||
| 71 | /** | |
| 72 | * The method builds a usual TermNode and then checks if an interpreter can | |
| 73 | * be found that | |
| 74 | * would agree to interpret the relevant terms (children nodes) and deliver a | |
| 75 | * definite result. | |
| 76 | * If no such interpreter is found, a PolicyParsingException is thrown; | |
| 77 | * otherwise, the | |
| 78 | * interpreter will be used by the evaluate method, and the result type | |
| 79 | * reported by the canEvaluate | |
| 80 | * method of the interpreter will be returned by the getType method. | |
| 81 | */ | |
| 82 | 144 |
public void construct() throws issrg.pba.rbac.PolicyParsingException { |
| 83 | 144 | super.construct(); |
| 84 | ||
| 85 | 144 | Interpreter[] ints = TermNode.getInterpretersForNode(getName()); |
| 86 | 144 | if (ints!=null){ |
| 87 | 272 | for (int i=0; i<ints.length; i++){ |
| 88 | 0 | if ((type=ints[i].canEvaluate(terms))!=null){ // can evaluate; terms has been set by the super.construct(); this automatically sets the type of the result, too |
| 89 | 144 | interpreter=ints[i]; |
| 90 | 144 | break; |
| 91 | } | |
| 92 | } | |
| 93 | } | |
| 94 | ||
| 95 | 144 | if (interpreter==null){ |
| 96 | 0 | throw new issrg.pba.rbac.PolicyParsingException("No interpreter for such combination of operands has been found for node "+getName()); |
| 97 | } | |
| 98 | } | |
| 99 | ||
| 100 | 323 |
public String getType(){ |
| 101 | 323 | return type; // evaluated during the call to construct() |
| 102 | } | |
| 103 | ||
| 104 | /** | |
| 105 | * This method evaluates the expression given the environment. It uses the | |
| 106 | * Interpreter found during the call to construct(); | |
| 107 | * | |
| 108 | * @param env - the Environment with the variables in it | |
| 109 | * | |
| 110 | * @return the Interpreter-specific object, guaranteed to be of type returned | |
| 111 | * by getType() | |
| 112 | * | |
| 113 | * @throws EvaluationException, if there was a problem evaluating the | |
| 114 | * expression | |
| 115 | */ | |
| 116 | 229 |
public Object evaluate(Environment env) throws EvaluationException{ |
| 117 | 229 | try{ |
| 118 | 229 | return interpreter.evaluate(env, terms); |
| 119 | }catch (EvaluationException ee){ | |
| 120 | 0 | throw ee; |
| 121 | }catch (Throwable th){ | |
| 122 | 0 | throw new EvaluationException("Run-time error", th); |
| 123 | } | |
| 124 | } | |
| 125 | } | |
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