| 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.util.HashMap; |
| 18 | import java.util.Map; |
| 19 | |
| 20 | /** |
| 21 | * Event filter that is based on a constraint expressed in a specific language, |
| 22 | * OCL (Object Constraint Language). |
| 23 | * Allows to easily define filters that have complex constraints. |
| 24 | * <p> |
| 25 | * The OCL is a simple language that allows evaluation of a boolean expression |
| 26 | * based on various operators (comparison, boolean arithmetic). It also can |
| 27 | * reflect any property of the vent to be evaluated (for further checks). |
| 28 | * <p> |
| 29 | * Example: |
| 30 | * <pre> |
| 31 | * event.id != 0 && (event.type == 1 || event.type == 2) && event.priority > 2 |
| 32 | * </pre> |
| 33 | * In that example <code>event</code> is the variable name that can be used to |
| 34 | * represent the event to be evaluated by the filter. |
| 35 | * |
| 36 | * @author Jean-Francois Poilpret |
| 37 | */ |
| 38 | public class ConstraintFilter<T> implements Filter<T> |
| 39 | { |
| 40 | static final public String EVENT_NAME = "event"; |
| 41 | |
| 42 | /** |
| 43 | * Build a new ConstraintFilter. |
| 44 | * @param constraint the expression to evaluate for each event |
| 45 | * @param eventClass class of the event (used for event reflection control) |
| 46 | */ |
| 47 | public ConstraintFilter(String constraint, Class eventClass) |
| 48 | { |
| 49 | Map<String, Class> classes = new HashMap<String, Class>(); |
| 50 | classes.put(EVENT_NAME, eventClass); |
| 51 | init(constraint, classes, new HashMap<String, Object>()); |
| 52 | } |
| 53 | |
| 54 | /** |
| 55 | * Build a new ConstraintFilter with one additional variable in the |
| 56 | * expression. |
| 57 | * <p> |
| 58 | * This is seldom used. |
| 59 | * |
| 60 | * @param constraint the expression to evaluate for each event |
| 61 | * @param eventClass class of the event (used for event reflection control) |
| 62 | * @param argName the name of the additional variable (as used in the |
| 63 | * constraint expression) |
| 64 | * @param argClass the class of the additional variable (used for reflection |
| 65 | * control) |
| 66 | * @param argValue the value of the additional variable |
| 67 | */ |
| 68 | public ConstraintFilter(String constraint, |
| 69 | Class eventClass, |
| 70 | String argName, |
| 71 | Class argClass, |
| 72 | Object argValue) |
| 73 | { |
| 74 | Map<String, Class> classes = new HashMap<String, Class>(); |
| 75 | classes.put(EVENT_NAME, eventClass); |
| 76 | classes.put(argName, argClass); |
| 77 | Map<String, Object> variables = new HashMap<String, Object>(); |
| 78 | variables.put(argName, argValue); |
| 79 | init(constraint, classes, variables); |
| 80 | } |
| 81 | |
| 82 | /** |
| 83 | * Build a new ConstraintFilter with additional variables in the |
| 84 | * expression. |
| 85 | * <p> |
| 86 | * This is seldom used. |
| 87 | * |
| 88 | * @param constraint the expression to evaluate for each event |
| 89 | * @param classes the classes of additional variables (used for reflection |
| 90 | * control) indexed by name (must contain "event") |
| 91 | * @param values the values of additional variables indexed by name (must |
| 92 | * contain "event") |
| 93 | */ |
| 94 | public ConstraintFilter(String constraint, |
| 95 | Map<String, Class> classes, |
| 96 | Map<String, Object> values) |
| 97 | { |
| 98 | init(constraint, classes, values); |
| 99 | } |
| 100 | |
| 101 | private void init( String constraint, |
| 102 | Map<String, Class> classes, |
| 103 | Map<String, Object> values) |
| 104 | { |
| 105 | _evaluator = new ConstraintEvaluator(constraint, classes); |
| 106 | _variables = values; |
| 107 | } |
| 108 | |
| 109 | public boolean passEvent(T event) |
| 110 | { |
| 111 | Map<String, Object> variables = new HashMap<String, Object>(); |
| 112 | variables.putAll(_variables); |
| 113 | variables.put(EVENT_NAME, event); |
| 114 | return _evaluator.evaluate(variables); |
| 115 | } |
| 116 | |
| 117 | private ConstraintEvaluator _evaluator; |
| 118 | private Map<String, Object> _variables; |
| 119 | } |