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 }