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It is possible to fully integrate the Atomikos transaction manager into Tomcat. Doing it this way makes the transaction manager shared across all web applications exactly like with any full-blown J2EE server.

Important note

When the Atomikos transaction manager is installed globally in Tomcat, you now must also install your JDBC driver at the same global location (ie: into the TOMCAT_HOME/lib folder). If you dont do that, you will get a NoClassDefFoundErrors or a ClassNotFoundException or even a ClassCastException during your web application deployment.

This is not a limitation of Atomikos nor of Tomcat but of the J2EE class loading design that both Tomcat and Atomikos must follow.

Installation

Installation is quite simple, it just involves copying some JAR files, a property file and editing some Tomcat configuration files.

Copying Atomikos Tomcat Lifecycle library

• Drop this JAR file into the TOMCAT_HOME/lib folder: atomikos-tomcat-lifecycle.jar

This JAR contains a single class file that is a Tomcat lifecycle listener: it listens for Tomcat's startup and shutdown events and start or stop the transaction manager accordingly. Here is its source code:

Atomikos Lifecycle Listener.java

package com.atomikos.tomcat;

import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleEvent;
import org.apache.catalina.LifecycleListener;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.atomikos.icatch.jta.UserTransactionManager;
import com.atomikos.icatch.system.Configuration;

public class AtomikosLifecycleListener implements LifecycleListener {

   private static Log log = LogFactory.getLog(AtomikosLifecycleListener.class);

   private UserTransactionManager utm;

   public void lifecycleEvent(LifecycleEvent event) {
      if (Lifecycle.START_EVENT.equals(event.getType())) {
         if (utm == null) {
            log.info("starting Atomikos Transaction Manager " + Configuration.VERSION);
            utm = new UserTransactionManager();
         }
      }
      else if (Lifecycle.STOP_EVENT.equals(event.getType())) {
         if (utm != null) {
            log.info("shutting down Atomikos Transaction Manager");
            utm.close();
         }
      }
   }

}

Copying Atomikos Tomcat BeanFactory library

• Drop this JAR file into the TOMCAT_HOME/lib folder: atomikos-tomcat-beanfactory.jar

This JAR contains a single class file that is an enhanced version of Tomcat JNDI's Bean Factory. Here is its source code:

Bean Factory.java

package com.atomikos.tomcat;

import java.util.Hashtable;
import java.util.Enumeration;
import javax.naming.Name;
import javax.naming.Context;
import javax.naming.NamingException;
import javax.naming.Reference;
import javax.naming.RefAddr;
import javax.naming.spi.ObjectFactory;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.naming.ResourceRef;
import org.apache.naming.factory.Constants;

import com.atomikos.beans.PropertyUtils;
import com.atomikos.jdbc.AtomikosDataSourceBean;

public class BeanFactory implements ObjectFactory {

    private final static Log log = LogFactory.getLog(BeanFactory.class);

    public Object getObjectInstance (
    Object obj, Name name, Context nameCtx, Hashtable environment) 
    throws NamingException {
        if (obj instanceof ResourceRef) {
            try {
                Reference ref = (Reference) obj;
                String beanClassName = ref.getClassName();
                Class beanClass = null;
                ClassLoader tcl = Thread.currentThread().getContextClassLoader();
                if (tcl != null) {
                    try {
                        beanClass = tcl.loadClass(beanClassName);
                    } catch(ClassNotFoundException e) {
                    }
                } else {
                    try {
                        beanClass = Class.forName(beanClassName);
                    } catch(ClassNotFoundException e) {
                        e.printStackTrace();
                    }
                }
                if (beanClass == null) {
                    throw new NamingException("Class not found: " + beanClassName);
                }
                if (!AtomikosDataSourceBean.class.isAssignableFrom(beanClass)) {
                    throw new NamingException(
                    "Class is not a AtomikosDataSourceBean: " + beanClassName);
                }

                if (log.isDebugEnabled()) 
                    log.debug("instanciating bean of class " + beanClass.getName());

                AtomikosDataSourceBean bean = 
                   (AtomikosDataSourceBean) beanClass.newInstance();

                int i=0;
                Enumeration en = ref.getAll();
                while (en.hasMoreElements()) {
                    RefAddr ra = (RefAddr) en.nextElement();
                    String propName = ra.getType();

                    if (propName.equals(Constants.FACTORY) || 
                        propName.equals("scope") || 
                        propName.equals("auth")) {
                        continue;
                    }

                    String value = (String) ra.getContent();

                    if (log.isDebugEnabled()) 
                        log.debug("setting property '" + propName + 
                        "' to '" + value + "'");

                    PropertyUtils.setProperty(bean, propName, value);

                    i++;
                }

                if (log.isDebugEnabled()) 
                   log.debug("done setting " + i + " property(ies), 
                   now initializing resource " + bean);

                bean.init();
                return bean;

            } catch (Exception ex) {
                throw (NamingException) new NamingException(
                "error creating AtomikosDataSourceBean").initCause(ex);
            }

        } else {
            return null;
        }

    }
}

Copying TransactionsEssentials libraries

• Drop the following JARs from the Atomikos distribution into the TOMCAT_HOME/libfolder:
  • transactions.jar
  • transactions-api.jar
  • transactions-jta.jar
  • transactions-jdbc.jar
  • atomikos-util.jar.jar
  • jta.jar

You should also copy the transactions-hibernate3.jar and/or transactions-hibernate2.jar at the same location if you're planning to use Hibernate.

Copying Atomikos configuration file

• Drop the following properties file into the TOMCAT_HOME/lib folder: jta.properties

Edit server.xml

Then edit the TOMCAT_HOME/conf/server.xml file. At the beginning of the file you should see these four lines:

  <Listener className="org.apache.catalina.core.AprLifecycleListener" />
  <Listener className="org.apache.catalina.mbeans.ServerLifecycleListener" />
  <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" />
  <Listener className="org.apache.catalina.storeconfig.StoreConfigLifecycleListener"/>

Right after the last one, add this fifth one:

 <Listener className="com.atomikos.tomcat.AtomikosLifecycleListener" />

Edit context.xml

Then edit the TOMCAT_HOME/conf/context.xml file. At the beginning of the file you should see this line:

 <WatchedResource>WEB-INF/web.xml</WatchedResource>

Right after it, add that one:

 <Transaction factory="com.atomikos.icatch.jta.UserTransactionFactory" />

Example application

Here is a sample application that demonstrates how you can run TransactionsEssentials in a web application after it has been globally installed.

It is a simple blueprint application that shows and updates the content of a single Derby database.

Download the sample application here: dbtest.war

To install it, simply copy the WAR file in Tomcat's webapps folder. You also need to install Derby's JDBC driver in TOMCAT_HOME/lib.

You can then access it via this URL: http://localhost:8080/dbtest/.

Notes

• This demo uses an embedded Derby database. If it doesn't exist a new one is created in TOMCAT_HOME/work or else, the existing one is reused.
• The transactions logs and debug logs are stored in TOMCAT_HOME/work.
• You should get logs during Tomcat's startup and shutdown:
  • during startup: INFO: starting Atomikos Transaction Manager 3.3.0
  • during shutdown: INFO: shutting down Atomikos Transaction Manager

Using MySQL

The example uses Derby - however it can be configured with MySQL by changing the webapp context similar to this:

<?xml version="1.0" encoding="UTF-8"?>
<Context path="/dbtest" docBase="dbtest.war"
reloadable="true" crossContext="true">
<!-- Resource configuration for JDBC datasource-->
<Resource
name="jdbc/myDB"
auth="Container"
type="com.atomikos.jdbc.AtomikosDataSourceBean"
factory="com.atomikos.tomcat.BeanFactory"
uniqueResourceName="jdbc/myDB"
xaDataSourceClassName="com.mysql.jdbc.jdbc2.optional.MysqlXADataSource"
xaProperties.databaseName="test"
xaProperties.serverName="localhost"
xaProperties.port="3306"
xaProperties.user="USER"
xaProperties.password="PASSWORD"
xaProperties.url="jdbc:mysql://localhost:3306/test"
/>
</Context>

Remember to change the parameter values to your specific environment…

Using WebSphere MQ

This example shows how to define pooled JMS Queue Connection Factories and Queues for WebSphere MQ. Note that the uniqueResourceName MUST contain the text MQSeries_XA_RMI.

<?xml version="1.0" encoding="UTF-8"?>
<Context path="/dbtest" docBase="dbtest.war"
reloadable="true" crossContext="true">

<Resource 
name="jms/myQCF" 
auth="Container" 
type="com.atomikos.jms.AtomikosConnectionFactoryBean" 
factory="com.atomikos.tomcat.EnhancedTomcatAtomikosBeanFactory" 
uniqueResourceName="myQCF_MQSeries_XA_RMI" 
xaConnectionFactoryClassName="com.ibm.mq.jms.MQXAQueueConnectionFactory" 
xaProperties.queueManager="XXXX" 
xaProperties.hostName="hostname" 
xaProperties.port="1426" 
xaProperties.channel="XXXX" 
maxPoolSize="3" 
minPoolSize="1" />

<Resource name="jms/myQ" 
auth="Container" 
type="com.ibm.mq.jms.MQQueue" 
factory="com.ibm.mq.jms.MQQueueFactory" 
description="JMS Queue for reading messages" 
QU="MYQ.IN" 
CCSID="819" 
persistence="2" />         
</Context>

For this to work, you need an improved version of the Bean Factory described above, which can also handle JMS Connection Factory Beans:

EnhancedTomcatAtomikosBeanFactory .java

package com.atomikos.tomcat;

import java.util.Hashtable;
import java.util.Enumeration;

import javax.jms.JMSException;
import javax.naming.Name;
import javax.naming.Context;
import javax.naming.NamingException;
import javax.naming.Reference;
import javax.naming.RefAddr;
import javax.naming.spi.ObjectFactory;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.naming.ResourceRef;
import org.apache.naming.factory.Constants;

import com.atomikos.beans.PropertyException;
import com.atomikos.beans.PropertyUtils;
import com.atomikos.jdbc.AtomikosDataSourceBean;
import com.atomikos.jdbc.AtomikosSQLException;
import com.atomikos.jms.AtomikosConnectionFactoryBean;

/**
 * enhancement of com.atomikos.tomcat.BeanFactory (see http://www.atomikos.com/Documentation/Tomcat6Integration33)
 *
 */
public class EnhancedTomcatAtomikosBeanFactory implements ObjectFactory {

    private final static Log log = LogFactory.getLog(RSFTomcatAtomikosBeanFactory.class);

    public Object getObjectInstance (Object obj, Name name, Context nameCtx, Hashtable<?,?> environment) 
    throws NamingException {
        if (obj instanceof ResourceRef) {
            try {
                Reference ref = (Reference) obj;
                String beanClassName = ref.getClassName();
                Class<?> beanClass = null;
                ClassLoader tcl = Thread.currentThread().getContextClassLoader();
                if (tcl != null) {
                    try {
                        beanClass = tcl.loadClass(beanClassName);
                    } catch(ClassNotFoundException e) {
                    }
                } else {
                    try {
                        beanClass = Class.forName(beanClassName);
                    } catch(ClassNotFoundException e) {
                        e.printStackTrace();
                    }
                }
                if (beanClass == null) {
                    throw new NamingException("Class not found: " + beanClassName);
                }
                if (AtomikosDataSourceBean.class.isAssignableFrom(beanClass))
                {
                   return createDataSourceBean(ref, (Class<? extends AtomikosDataSourceBean>)beanClass);
                }
                else if (AtomikosConnectionFactoryBean.class.isAssignableFrom(beanClass))
                {
                   return createConnectionFactoryBean(ref, (Class<? extends AtomikosConnectionFactoryBean>)beanClass);
                }
                else
                {
                    throw new NamingException(
                    "Class is neither an AtomikosDataSourceBean nor an AtomikosConnectionFactoryBean: " + beanClassName);
                }

            } catch (Exception ex) {
                throw (NamingException) new NamingException(
                "error creating AtomikosDataSourceBean").initCause(ex);
            }

        } else {
            return null;
        }

    }

    /**
    * create a DataSourceBean for a JMS datasource
    * @param ref
    * @param beanClass
    * @return
    * @throws InstantiationException
    * @throws IllegalAccessException
    * @throws PropertyException
    * @throws AtomikosSQLException
     * @throws JMSException 
    */
   private Object createConnectionFactoryBean(Reference ref, Class<? extends AtomikosConnectionFactoryBean> beanClass) throws InstantiationException, IllegalAccessException, PropertyException,
      JMSException
   {
      if (log.isDebugEnabled()) 
          log.debug("instanciating bean of class " + beanClass.getName());

      AtomikosConnectionFactoryBean bean = 
         (AtomikosConnectionFactoryBean) beanClass.newInstance();

      int i=0;
      Enumeration<RefAddr> en = ref.getAll();
      while (en.hasMoreElements()) {
          RefAddr ra = (RefAddr) en.nextElement();
          String propName = ra.getType();

          if (propName.equals(Constants.FACTORY) || 
              propName.equals("scope") || 
              propName.equals("auth")) {
              continue;
          }

          String value = (String) ra.getContent();

          if (log.isDebugEnabled()) 
              log.debug("setting property '" + propName + 
              "' to '" + value + "'");

          PropertyUtils.setProperty(bean, propName, value);

          i++;
      }

      if (log.isDebugEnabled()) 
         log.debug("done setting " + i + " property(ies), now initializing resource " + bean);

      bean.init();
      return bean;
   }

   /**
    * create a DataSourceBean for a JDBC datasource
    * @param ref
    * @param beanClass
    * @return
    * @throws InstantiationException
    * @throws IllegalAccessException
    * @throws PropertyException
    * @throws AtomikosSQLException
    */
   private Object createDataSourceBean(Reference ref, Class<? extends AtomikosDataSourceBean> beanClass) throws InstantiationException, IllegalAccessException, PropertyException,
      AtomikosSQLException
   {
      if (log.isDebugEnabled()) 
          log.debug("instanciating bean of class " + beanClass.getName());

      AtomikosDataSourceBean bean = 
         (AtomikosDataSourceBean) beanClass.newInstance();

      int i=0;
      Enumeration<RefAddr> en = ref.getAll();
      while (en.hasMoreElements()) {
          RefAddr ra = (RefAddr) en.nextElement();
          String propName = ra.getType();

          if (propName.equals(Constants.FACTORY) || 
              propName.equals("scope") || 
              propName.equals("auth")) {
              continue;
          }

          String value = (String) ra.getContent();

          if (log.isDebugEnabled()) 
              log.debug("setting property '" + propName + 
              "' to '" + value + "'");

          PropertyUtils.setProperty(bean, propName, value);

          i++;
      }

      if (log.isDebugEnabled()) 
         log.debug("done setting " + i + " property(ies), now initializing resource " + bean);

      bean.init();
      return bean;
   }
}