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.closure;
017    
018    import org.springframework.rules.closure.support.AbstractClosure;
019    import org.springframework.util.Assert;
020    
021    /**
022     * Conveneince support class for binary closures. Overrides call(argument) to
023     * treat the passed argument as an array with two elements.
024     * 
025     * @author Keith Donald
026     */
027    public abstract class AbstractBinaryClosure extends AbstractClosure implements
028            BinaryClosure {
029        public Object call(Object argument) {
030            if (argument == null) {
031                argument = new Object[0];
032            }
033            Assert.isTrue(argument.getClass().isArray(),
034                    "Binary argument must be an array");
035            Object[] arguments = (Object[])argument;
036            Assert.isTrue(arguments.length == 2,
037                    "Binary argument must contain 2 elements");
038            return call(arguments[0], arguments[1]);
039        }
040    
041    }