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     */
017    package org.apache.camel.bam;
018    
019    import org.apache.camel.Exchange;
020    import org.apache.camel.Expression;
021    import org.apache.camel.Processor;
022    import org.apache.camel.RuntimeCamelException;
023    import org.apache.commons.logging.Log;
024    import org.apache.commons.logging.LogFactory;
025    import org.springframework.transaction.support.TransactionTemplate;
026    import org.springframework.transaction.support.TransactionCallbackWithoutResult;
027    import org.springframework.transaction.support.TransactionCallback;
028    import org.springframework.transaction.TransactionStatus;
029    import org.springframework.transaction.TransactionException;
030    
031    import java.lang.reflect.Type;
032    import java.lang.reflect.ParameterizedType;
033    
034    /**
035     * A {@link Processor} for working on
036     * <a href="http://activemq.apache.org/camel/bam.html">BAM</a>
037     *
038     * @version $Revision: $
039     */
040    public abstract class BamProcessorSupport<T> implements Processor {
041        private static final transient Log log = LogFactory.getLog(BamProcessorSupport.class);
042    
043        private Class<T> entityType;
044        private Expression<Exchange> correlationKeyExpression;
045        private TransactionTemplate transactionTemplate;
046    
047    
048        protected BamProcessorSupport(TransactionTemplate transactionTemplate, Expression<Exchange> correlationKeyExpression) {
049            this.transactionTemplate = transactionTemplate;
050            this.correlationKeyExpression = correlationKeyExpression;
051    
052            Type type = getClass().getGenericSuperclass();
053            if (type instanceof ParameterizedType) {
054                ParameterizedType parameterizedType = (ParameterizedType) type;
055                Type[] arguments = parameterizedType.getActualTypeArguments();
056                if (arguments.length > 0) {
057                    Type argumentType = arguments[0];
058                    if (argumentType instanceof Class) {
059                        this.entityType = (Class<T>) argumentType;
060                    }
061                }
062            }
063            if (entityType == null) {
064                throw new IllegalArgumentException("Could not infer the entity type!");
065            }
066        }
067    
068        protected BamProcessorSupport(TransactionTemplate transactionTemplate, Expression<Exchange> correlationKeyExpression, Class<T> entitytype) {
069            this.transactionTemplate = transactionTemplate;
070            this.entityType = entitytype;
071            this.correlationKeyExpression = correlationKeyExpression;
072        }
073    
074        public void process(final Exchange exchange) {
075            try {
076                Object entity = transactionTemplate.execute(new TransactionCallback() {
077                    public Object doInTransaction(TransactionStatus status) {
078                        try {
079                            Object key = getCorrelationKey(exchange);
080    
081                            T entity = loadEntity(exchange, key);
082    
083                            log.info("Correlation key: " + key + " with entity: " + entity);
084    
085                            //storeProcessInExchange(exchange, entity);
086                            processEntity(exchange, entity);
087    
088                            return entity;
089                        }
090                        catch (Exception e) {
091                            throw new RuntimeCamelException(e);
092                        }
093                }});
094    
095                log.info("After transaction process instance is: " + entity);
096            }
097            catch (Throwable e) {
098                log.error("Caught: " + e, e);            
099            }
100        }
101    
102        // Properties
103        //-----------------------------------------------------------------------
104        public Expression<Exchange> getCorrelationKeyExpression() {
105            return correlationKeyExpression;
106        }
107    
108    
109        public Class<T> getEntityType() {
110            return entityType;
111        }
112    
113        // Implemenation methods
114        //-----------------------------------------------------------------------
115        protected abstract void processEntity(Exchange exchange, T entity) throws Exception;
116    
117        protected abstract T loadEntity(Exchange exchange, Object key);
118    
119    
120        protected Object getCorrelationKey(Exchange exchange) throws NoCorrelationKeyException {
121            Object value = correlationKeyExpression.evaluate(exchange);
122            if (value == null) {
123                throw new NoCorrelationKeyException(this, exchange);
124            }
125            return value;
126        }
127    }