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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.camel.support;

import org.apache.camel.CamelContext;
import org.apache.camel.Exchange;
import org.apache.camel.TypeConverter;

/**
 * A helper class for developers wishing to implement an {@link org.apache.camel.Expression} using Java code with a
 * minimum amount of code to write so that the developer only needs to implement one of the
 * {@link #evaluate(org.apache.camel.Exchange, Class)} or {@link #evaluate(org.apache.camel.Exchange)} methods.
 */
public abstract class ExpressionAdapter extends ExpressionSupport {

    private TypeConverter converter;

    @Override
    public void init(CamelContext context) {
        super.init(context);
        this.converter = context.getTypeConverter();
    }

    @Override
    protected String assertionFailureMessage(Exchange exchange) {
        return toString();
    }

    @Override
    public  T evaluate(Exchange exchange, Class type) {
        Object value = evaluate(exchange);
        if (Object.class == type) {
            // do not use type converter if type is Object (optimize)
            return (T) value;
        }
        if (converter != null) {
            // optimized to use converter from init
            return converter.convertTo(type, exchange, value);
        } else {
            return exchange.getContext().getTypeConverter().convertTo(type, exchange, value);
        }
    }

}