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.dao.DataIntegrityViolationException;
026 import org.springframework.orm.jpa.JpaSystemException;
027 import org.springframework.transaction.TransactionStatus;
028 import org.springframework.transaction.support.TransactionCallback;
029 import org.springframework.transaction.support.TransactionTemplate;
030
031 import javax.persistence.EntityExistsException;
032 import java.lang.reflect.ParameterizedType;
033 import java.lang.reflect.Type;
034
035 /**
036 * A base {@link Processor} for working on <a
037 * href="http://activemq.apache.org/camel/bam.html">BAM</a> which a derived
038 * class would do the actual persistence such as the {@link JpaBamProcessor}
039 *
040 * @version $Revision: $
041 */
042 public abstract class BamProcessorSupport<T> implements Processor {
043 private static final transient Log LOG = LogFactory.getLog(BamProcessorSupport.class);
044 private Class<T> entityType;
045 private Expression<Exchange> correlationKeyExpression;
046 private TransactionTemplate transactionTemplate;
047 private int maximumRetries = 30;
048
049 public int getMaximumRetries() {
050 return maximumRetries;
051 }
052
053 public void setMaximumRetries(int maximumRetries) {
054 this.maximumRetries = maximumRetries;
055 }
056
057 protected BamProcessorSupport(TransactionTemplate transactionTemplate, Expression<Exchange> correlationKeyExpression) {
058 this.transactionTemplate = transactionTemplate;
059 this.correlationKeyExpression = correlationKeyExpression;
060
061 Type type = getClass().getGenericSuperclass();
062 if (type instanceof ParameterizedType) {
063 ParameterizedType parameterizedType = (ParameterizedType) type;
064 Type[] arguments = parameterizedType.getActualTypeArguments();
065 if (arguments.length > 0) {
066 Type argumentType = arguments[0];
067 if (argumentType instanceof Class) {
068 this.entityType = (Class<T>) argumentType;
069 }
070 }
071 }
072 if (entityType == null) {
073 throw new IllegalArgumentException("Could not infer the entity type!");
074 }
075 }
076
077 protected BamProcessorSupport(TransactionTemplate transactionTemplate, Expression<Exchange> correlationKeyExpression, Class<T> entitytype) {
078 this.transactionTemplate = transactionTemplate;
079 this.entityType = entitytype;
080 this.correlationKeyExpression = correlationKeyExpression;
081 }
082
083 public void process(final Exchange exchange) {
084 Object entity = null;
085 for (int i = 0; entity == null && i < maximumRetries; i++) {
086 if (i > 0) {
087 LOG.info("Retry attempt due to duplicate row: " + i);
088 }
089 entity = transactionTemplate.execute(new TransactionCallback() {
090 public Object doInTransaction(TransactionStatus status) {
091 try {
092 Object key = getCorrelationKey(exchange);
093
094 T entity = loadEntity(exchange, key);
095
096 if (LOG.isDebugEnabled()) {
097 LOG.debug("Correlation key: " + key + " with entity: " + entity);
098 }
099 processEntity(exchange, entity);
100
101 return entity;
102 }
103 catch (JpaSystemException e) {
104 if (LOG.isDebugEnabled()) {
105 LOG.debug("Likely exception is due to duplicate row in concurrent setting: " + e, e);
106 }
107 LOG.info("Attempt to insert duplicate row due to concurrency issue, so retrying: " + e);
108 return retryDueToDuplicate(status);
109 }
110 catch (DataIntegrityViolationException e) {
111 Throwable throwable = e.getCause();
112 if (throwable instanceof EntityExistsException) {
113 LOG.info("Attempt to insert duplicate row due to concurrency issue, so retrying: " + throwable);
114 return retryDueToDuplicate(status);
115 }
116 return onError(status, throwable);
117 }
118 catch (Throwable e) {
119 return onError(status, e);
120 }
121 }
122 });
123 }
124 }
125
126 // Properties
127 // -----------------------------------------------------------------------
128 public Expression<Exchange> getCorrelationKeyExpression() {
129 return correlationKeyExpression;
130 }
131
132 public Class<T> getEntityType() {
133 return entityType;
134 }
135
136 // Implemenation methods
137 // -----------------------------------------------------------------------
138 protected abstract void processEntity(Exchange exchange, T entity) throws Exception;
139
140 protected abstract T loadEntity(Exchange exchange, Object key);
141
142 protected Object getCorrelationKey(Exchange exchange) throws NoCorrelationKeyException {
143 Object value = correlationKeyExpression.evaluate(exchange);
144 if (value == null) {
145 throw new NoCorrelationKeyException(this, exchange);
146 }
147 return value;
148 }
149
150 protected Object retryDueToDuplicate(TransactionStatus status) {
151 status.setRollbackOnly();
152 return null;
153 }
154
155 protected Object onError(TransactionStatus status, Throwable e) {
156 status.setRollbackOnly();
157 LOG.error("Caught: " + e, e);
158 throw new RuntimeCamelException(e);
159 }
160 }