| 1 | // Copyright 2004-2007 Jean-Francois Poilpret |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | // you may not use this file except in compliance with the License. |
| 5 | // You may obtain a copy of the License at |
| 6 | // |
| 7 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | // |
| 9 | // Unless required by applicable law or agreed to in writing, software |
| 10 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | // See the License for the specific language governing permissions and |
| 13 | // limitations under the License. |
| 14 | |
| 15 | package net.sourceforge.hiveevents; |
| 16 | |
| 17 | import java.io.StringReader; |
| 18 | import java.util.Map; |
| 19 | |
| 20 | import org.apache.commons.logging.Log; |
| 21 | import org.apache.commons.logging.LogFactory; |
| 22 | |
| 23 | import org.apache.hivemind.ApplicationRuntimeException; |
| 24 | |
| 25 | import antlr.CommonAST; |
| 26 | import antlr.RecognitionException; |
| 27 | import antlr.TokenStreamException; |
| 28 | |
| 29 | /** |
| 30 | * Utility class to evaluate an OCL (Object Constraint Language) expression. |
| 31 | * |
| 32 | * @author Jean-Francois Poilpret |
| 33 | */ |
| 34 | public class ConstraintEvaluator |
| 35 | { |
| 36 | static private final Log _logger = LogFactory.getLog(ConstraintEvaluator.class); |
| 37 | |
| 38 | /** |
| 39 | * Build a new evaluator for a constraint expression. |
| 40 | * The expression is immediately parsed and it its AST (abstract syntax tree) |
| 41 | * calculated for later evaluation with actual variable values. |
| 42 | * <p> |
| 43 | * Each instance is thread-safe and can thus be used by simultaneous threads |
| 44 | * to evaluate the same expression with different variable values. |
| 45 | * |
| 46 | * @param constraint the expression to be evaluated later |
| 47 | * @param variableClasses the classes of all variables appearing in |
| 48 | * <code>constraint</code> indexed by name (used for reflection checks) |
| 49 | */ |
| 50 | public ConstraintEvaluator(String constraint, Map<String, Class> variableClasses) |
| 51 | { |
| 52 | try |
| 53 | { |
| 54 | _constraint = constraint; |
| 55 | ConstraintLexer lexer = new ConstraintLexer(new StringReader(constraint)); |
| 56 | lexer.setFilename(constraint); |
| 57 | lexer.initVariables(variableClasses); |
| 58 | |
| 59 | ConstraintParser parser = new ConstraintParser(lexer); |
| 60 | parser.setFilename(constraint); |
| 61 | // Parse the input expression |
| 62 | parser.expr(); |
| 63 | _tree = (CommonAST) parser.getAST(); |
| 64 | if (_logger.isDebugEnabled()) |
| 65 | { |
| 66 | _logger.debug( "<init> constraint <" + constraint + "> AST = " + |
| 67 | _tree.toStringTree()); |
| 68 | } |
| 69 | } |
| 70 | catch (TokenStreamException e) |
| 71 | { |
| 72 | _logger.error("<init>", e); |
| 73 | throw new ApplicationRuntimeException( |
| 74 | "Problem parsing <" + constraint + ">", e); |
| 75 | } |
| 76 | catch (RecognitionException e) |
| 77 | { |
| 78 | _logger.error("<init>", e); |
| 79 | throw new ApplicationRuntimeException( |
| 80 | "Problem parsing <" + constraint + ">", e); |
| 81 | } |
| 82 | } |
| 83 | |
| 84 | /** |
| 85 | * Evaluates the constraint expression with actual values for all variables. |
| 86 | * @param variables values for all variables, indexed by name |
| 87 | * @return the result of the expression evaluation |
| 88 | */ |
| 89 | public boolean evaluate(Map<String, Object> variables) |
| 90 | { |
| 91 | try |
| 92 | { |
| 93 | ConstraintTreeWalker walker = new ConstraintTreeWalker(); |
| 94 | walker.initVariables(variables); |
| 95 | // Traverse the tree created by the parser |
| 96 | return walker.expr(_tree); |
| 97 | } |
| 98 | catch (RecognitionException e) |
| 99 | { |
| 100 | _logger.error("evaluate()", e); |
| 101 | throw new ApplicationRuntimeException( |
| 102 | "Problem evaluating <" + _constraint + ">", e); |
| 103 | } |
| 104 | } |
| 105 | |
| 106 | final private String _constraint; |
| 107 | final private CommonAST _tree; |
| 108 | } |