001    /*
002     * Copyright 2002-2004 the original author or authors.
003     * 
004     * Licensed under the Apache License, Version 2.0 (the "License"); you may not
005     * use this file except in compliance with the License. You may obtain a copy of
006     * the License at
007     * 
008     * http://www.apache.org/licenses/LICENSE-2.0
009     * 
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
012     * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
013     * License for the specific language governing permissions and limitations under
014     * the License.
015     */
016    package org.springframework.rules.constraint;
017    
018    import org.springframework.rules.constraint.Constraint;
019    import org.springframework.util.Assert;
020    
021    /**
022     * "Nots" another unary constraint (the inverse) by using composition.
023     * 
024     * @author Keith Donald
025     */
026    public class Not implements Constraint {
027        private Constraint constraint;
028    
029        /**
030         * Creates a UnaryNot in temporary invalid state - please use only
031         * if you have to, the well-formed constructor is much preferred.
032         */
033        public Not() {
034            
035        }
036        
037        /**
038         * Creates a UnaryNot
039         * 
040         * @param constraint
041         *            The constraint to negate.
042         */
043        public Not(Constraint constraint) {
044            setConstraint(constraint);
045        }
046        
047        public void setConstraint(Constraint constraint) {
048            this.constraint = constraint;
049        }
050        
051        /**
052         * Negates the boolean result returned by testing the wrapped constraint.
053         * 
054         * @see Constraint#test(java.lang.Object)
055         */
056        public boolean test(Object value) {
057            Assert.state(constraint != null, "The constraint is not set");
058            return !constraint.test(value);
059        }
060        
061        public String toString() {
062            return "not(" + getConstraint() + ")";
063        }
064    
065        public Constraint getConstraint() {
066            return constraint;
067        }
068    
069    }