Easier and nicer JMS

JMS seems like a hostile ground. It has all it’s quirks and strange behaviours. A couple of defining standards plus esoteric brokers, queues and topics.

At work, we mainly use open source Jms solutions, namely Apache ActiveMQ. This one is usually bundled with Apache Servicemix, as a message broker for this particular ESB. As there are some minor caveats in this scennerio, I’d like to describe here some guidelines for getting to running JMS queues.

Treat this post as a quick cheat sheet with the most common things about JMS I tend to forget :)

Minor glitches encountered during work with embedded broker led to some thoughts about switching to external broker. This is how I configure SMX and AcviteMQ.

Necessary steps:

  • change apache-servicemix/conf/servicemix.properties activemq.port to sth else than standard, for example 61626
  • change apache-activemq/conf/activemq.xml with this settings:
    • change port, the service listens on:
    • setup separate JMX instance:
  • the nicest tool I found for browsing queues and topics is Hermes JMS. Sample config, that connects Hermes to ActiveMQ instance is on the picture below: HermesJMS to ActiveMQ connection config
  • sending simple messages with Hermes is basic, but what if you need to set some headers, send bulk messages, etc. Easy, just use Hermes xml format. Look like this code snippet below and is rather self-explanatory:
  • since we use lots of Apache Camel to consume messages, here is a simple way to start broker in your tests:
    • start a broker
              BrokerService broker = new org.apache.activemq.broker.BrokerService();

      Notice it has persistance disabled.

    • initialize Camel’s JMS component:
          ctx.addComponent("jms", ActiveMQComponent.activeMQComponent("tcp://localhost:51616"));
    • if you want to pass messages to reference endpoints, (like ref:input), use this wrapper method:
      private JmsEndpoint createJmsEndpoint(String endpoint) throws JMSException {
              ActiveMQComponent amqc = (ActiveMQComponent) ctx.getComponent("jms");
              JmsEndpoint endp = JmsEndpoint.newInstance(new ActiveMQTopic(endpoint), amqc);
              return endp;

These are all the tricks I’ve got for now! But if you know some other good tools that handle JMS, feel free to comment! Got more advices, again, comment!

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Zabawy zespołowe: ćwiczenie głosu – RYBA!

Ćwiczenie ma za zadanie ośmielić osoby do mówienia głośno i wyraźnie. Ma też pomóc ustawić głos. Bardzo przydatne przy spotkaniach typu stand-up, gdzie "mruki" opowiadają pod nosem, co ostatnio robiły. Z mojego doświadczenia - działa!

Osoby biorące udział w ćwiczeniu stają w okręgu. Wybieramy sobie słówko do powtarzania. Proponowana jest ryba, ale może to być dowolne inne, proste w wymowie słowo.
Prowadzący ustala kierunek i jako pierwszy mówi szeptem ryba. Następnie, kolejne osoby powtarzają rybę, aż do donośnego"RYBA. Jeśli warunki pozwalają, można nawet krzyczeć, ale nie wrzeszczeć, bo wtedy wymowa jest niewyraźna. Po osiągnięciu maksymalnego (w pewnym sensie, ustalonego poziomu), zaczynamy ściszać głos, aż do szeptu. Naturalnie zabawę można powtórzyć dowolną ilość razy.

Jako szept warto przećwiczyć szept aktorski, czyli używanie szeptu, ale głośnego i wyraźnego, bez tembru głosu.

Mając jedno ustalone słowo, fajnie jest potem mobilizować kogoś kto mówi zbyt cicho wołając tylko "ryba!" i wtedy wszystko wiadomo.

JBoss Envers and Spring transaction managers

I've stumbled upon a bug with my configuration for JBoss Envers today, despite having integration tests all over the application. I have to admit, it casted a dark shadow of doubt about the value of all the tests for a moment. I've been practicing TDD since 2005, and frankly speaking, I should have been smarter than that.

My fault was simple. I've started using Envers the right way, with exploratory tests and a prototype. Then I've deleted the prototype and created some integration tests using in-memory H2 that looked more or less like this example:

public void savingAndUpdatingPersonShouldCreateTwoHistoricalVersions() {
    Person person = createAndSavePerson();
    String oldFirstName = person.getFirstName();
    String newFirstName = oldFirstName + "NEW";

    updatePersonWithNewName(person, newFirstName);

    verifyTwoHistoricalVersionsWereSaved(oldFirstName, newFirstName);

private Person createAndSavePerson() {
    Transaction transaction = session.beginTransaction();
    Person person = PersonFactory.createPerson();
    return person;

private void updatePersonWithNewName(Person person, String newName) {
    Transaction transaction = session.beginTransaction();

private void verifyTwoHistoricalVersionsWereSaved(String oldFirstName, String newFirstName) {
    List<Object[]> personRevisions = getPersonRevisions();
    assertEquals(2, personRevisions.size());
    assertEquals(oldFirstName, ((Person)personRevisions.get(0)[0]).getFirstName());
    assertEquals(newFirstName, ((Person)personRevisions.get(1)[0]).getFirstName());

private List<Object[]> getPersonRevisions() {
    Transaction transaction = session.beginTransaction();
    AuditReader auditReader = AuditReaderFactory.get(session);
    List<Object[]> personRevisions = auditReader.createQuery()
            .forRevisionsOfEntity(Person.class, false, true)
    return personRevisions;

Because Envers inserts audit data when the transaction is commited (in a new temporary session), I thought I have to create and commit the transaction manually. And that is true to some point.

My fault was that I didn't have an end-to-end integration/acceptance test, that would call to entry point of the application (in this case a service which is called by GWT via RPC), because then I'd notice, that the Spring @Transactional annotation, and calling transaction.commit() are two, very different things.

Spring @Transactional annotation will use a transaction manager configured for the application. Envers on the other hand is used by subscribing a listener to hibernate's SessionFactory like this:

<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean" >        
 <property name="eventListeners">
     <map key-type="java.lang.String" value-type="org.hibernate.event.EventListeners">
         <entry key="post-insert" value-ref="auditEventListener"/>
         <entry key="post-update" value-ref="auditEventListener"/>
         <entry key="post-delete" value-ref="auditEventListener"/>
         <entry key="pre-collection-update" value-ref="auditEventListener"/>
         <entry key="pre-collection-remove" value-ref="auditEventListener"/>
         <entry key="post-collection-recreate" value-ref="auditEventListener"/>

<bean id="auditEventListener" class="org.hibernate.envers.event.AuditEventListener" />

Envers creates and collects something called AuditWorkUnits whenever you update/delete/insert audited entities, but audit tables are not populated until something calls AuditProcess.beforeCompletion, which makes sense. If you are using org.hibernate.transaction.JDBCTransaction manually, this is called on commit() when notifying all subscribed javax.transaction.Synchronization objects (and enver's AuditProcess is one of them).

The problem was, that I used a wrong transaction manager.

<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager" >
    <property name="dataSource" ref="dataSource"/>

This transaction manager doesn't know anything about hibernate and doesn't use org.hibernate.transaction.JDBCTransaction. While Synchronization is an interface from javax.transaction package, DataSourceTransactionManager doesn't use it (maybe because of simplicity, I didn't dig deep enough in org.springframework.jdbc.datasource), and thus Envers works fine except not pushing the data to the database.

Which is the whole point of using Envers.

Use right tools for the task, they say. The whole problem is solved by using a transaction manager that is well aware of hibernate underneath.

<bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager" >
    <property name="sessionFactory" ref="sessionFactory"/>

Lesson learned: always make sure your acceptance tests are testing the right thing. If there is a doubt about the value of your tests, you just don't have enough of them,