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.language.ref;
018
019import org.apache.camel.Exchange;
020import org.apache.camel.Expression;
021import org.apache.camel.IsSingleton;
022import org.apache.camel.Predicate;
023import org.apache.camel.builder.ExpressionBuilder;
024import org.apache.camel.spi.Language;
025import org.apache.camel.support.ExpressionAdapter;
026import org.apache.camel.util.ExpressionToPredicateAdapter;
027
028/**
029 * A language for referred expressions.
030 */
031public class RefLanguage implements Language, IsSingleton {
032
033    public static Expression ref(Object value) {
034        String ref = value.toString();
035        return ExpressionBuilder.refExpression(ref);
036    }
037
038    public Predicate createPredicate(String expression) {
039        return ExpressionToPredicateAdapter.toPredicate(createExpression(expression));
040    }
041
042    public Expression createExpression(final String expression) {
043        final Expression exp = RefLanguage.ref(expression);
044        return new ExpressionAdapter() {
045            public Object evaluate(Exchange exchange) {
046                Expression lookup = exp.evaluate(exchange, Expression.class);
047                if (lookup != null) {
048                    return lookup.evaluate(exchange, Object.class);
049                } else {
050                    throw new IllegalArgumentException("Cannot find expression in registry with ref: " + expression);
051                }
052            }
053
054            public String toString() {
055                return exp.toString();
056            }
057        };
058    }
059
060    public boolean isSingleton() {
061        return true;
062    }
063}