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; 027import org.apache.camel.util.PredicateToExpressionAdapter; 028 029/** 030 * A language for referred expressions or predicates. 031 */ 032public class RefLanguage implements Language, IsSingleton { 033 034 public static Expression ref(Object value) { 035 String ref = value.toString(); 036 return ExpressionBuilder.refExpression(ref); 037 } 038 039 public Predicate createPredicate(String expression) { 040 return ExpressionToPredicateAdapter.toPredicate(createExpression(expression)); 041 } 042 043 public Expression createExpression(final String expression) { 044 final Expression exp = RefLanguage.ref(expression); 045 return new ExpressionAdapter() { 046 public Object evaluate(Exchange exchange) { 047 Expression target = null; 048 049 Object lookup = exp.evaluate(exchange, Object.class); 050 051 // must favor expression over predicate 052 if (lookup instanceof Expression) { 053 target = (Expression) lookup; 054 } else if (lookup instanceof Predicate) { 055 target = PredicateToExpressionAdapter.toExpression((Predicate) lookup); 056 } 057 058 if (target != null) { 059 return target.evaluate(exchange, Object.class); 060 } else { 061 throw new IllegalArgumentException("Cannot find expression or predicate in registry with ref: " + expression); 062 } 063 } 064 065 public String toString() { 066 return exp.toString(); 067 } 068 }; 069 } 070 071 public boolean isSingleton() { 072 return true; 073 } 074}