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.builder;
018
019import org.apache.camel.BinaryPredicate;
020import org.apache.camel.Exchange;
021import org.apache.camel.Expression;
022import org.apache.camel.Predicate;
023
024import static org.apache.camel.util.ObjectHelper.notNull;
025
026/**
027 * A useful base class for {@link Predicate} implementations
028 *
029 * @version 
030 */
031public abstract class BinaryPredicateSupport implements BinaryPredicate {
032
033    private final Expression left;
034    private final Expression right;
035
036    protected BinaryPredicateSupport(Expression left, Expression right) {
037        notNull(left, "left");
038        notNull(right, "right");
039
040        this.left = left;
041        this.right = right;
042    }
043
044    @Override
045    public String toString() {
046        return left + " " + getOperationText() + " " + right;
047    }
048
049    public boolean matches(Exchange exchange) {
050        return matchesReturningFailureMessage(exchange) == null;
051    }
052
053    public String matchesReturningFailureMessage(Exchange exchange) {
054        // we must not store any state, so we can be thread safe
055        // and thus we offer this method which returns a failure message if
056        // we did not match
057        String answer = null;
058
059        // must be thread safe and store result in local objects
060        Object leftValue = left.evaluate(exchange, Object.class);
061        Object rightValue = right.evaluate(exchange, Object.class);
062        if (!matches(exchange, leftValue, rightValue)) {
063            answer = leftValue + " " + getOperator() + " " + rightValue;
064        }
065
066        return answer;
067    }
068
069    protected abstract boolean matches(Exchange exchange, Object leftValue, Object rightValue);
070
071    protected abstract String getOperationText();
072
073    public Expression getLeft() {
074        return left;
075    }
076
077    public Expression getRight() {
078        return right;
079    }
080
081    public String getOperator() {
082        return getOperationText();
083    }
084
085}