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