001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.camel;
018
019/**
020 * A predicate which evaluates a binary expression.
021 * <p/>
022 * The predicate has a left and right hand side expressions which
023 * is matched based on an operator.
024 * <p/>
025 * This predicate offers the {@link #matchesReturningFailureMessage} method
026 * which evaluates and returns a detailed failure message if the predicate did not match.
027 *
028 * @version 
029 */
030public interface BinaryPredicate extends Predicate {
031
032    /**
033     * Gets the operator
034     *
035     * @return the operator text
036     */
037    String getOperator();
038
039    /**
040     * Gets the left hand side expression
041     *
042     * @return the left expression
043     */
044    Expression getLeft();
045
046    /**
047     * Gets the right hand side expression
048     *
049     * @return the right expression
050     */
051    Expression getRight();
052
053    /**
054     * Evaluates the predicate on the message exchange and returns <tt>null</tt> if this
055     * exchange matches the predicate. If it did <b>not</b> match, then a failure message
056     * is returned detailing the reason, which can be used by end users to understand
057     * the failure.
058     *
059     * @param exchange the message exchange
060     * @return <tt>null</tt> if the predicate matches.
061     */
062    String matchesReturningFailureMessage(Exchange exchange);
063
064}