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 */
028public interface BinaryPredicate extends Predicate {
029
030    /**
031     * Gets the operator
032     *
033     * @return the operator text
034     */
035    String getOperator();
036
037    /**
038     * Gets the left hand side expression
039     *
040     * @return the left expression
041     */
042    Expression getLeft();
043
044    /**
045     * Gets the right hand side expression
046     *
047     * @return the right expression
048     */
049    Expression getRight();
050
051    /**
052     * Evaluates the predicate on the message exchange and returns <tt>null</tt> if this
053     * exchange matches the predicate. If it did <b>not</b> match, then a failure message
054     * is returned detailing the reason, which can be used by end users to understand
055     * the failure.
056     *
057     * @param exchange the message exchange
058     * @return <tt>null</tt> if the predicate matches.
059     */
060    String matchesReturningFailureMessage(Exchange exchange);
061
062}