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    /**
019     * A function object that tests one argument and returns a single
020     * <code>boolean</code> result.
021     * <p>
022     * A constraint tests a single argument against some conditional expression. For
023     * example, a "required" constraint will return true if the provided argument is
024     * non-null or empty, false otherwise.
025     * </p>
026     *
027     * @author Keith Donald
028     */
029    public interface Constraint {
030    
031            /**
032             * Test the provided argument against this predicate's condition.
033             *
034             * @param argument the argument value
035             * @return <code>true</code> if the condition was satisfied,
036             * <code>false</code> otherwise
037             */
038            boolean test(Object argument);
039    }