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## Chapter 43. Embedding HornetQ

HornetQ is designed as set of simple Plain Old Java Objects (POJOs). This means HornetQ can be instantiated and run in any dependency injection framework such as JBoss Microcontainer, Spring or Google Guice. It also means that if you have an application that could use messaging functionality internally, then it can directly instantiate HornetQ clients and servers in its own application code to perform that functionality. We call this embedding HornetQ.

Examples of applications that might want to do this include any application that needs very high performance, transactional, persistent messaging but doesn't want the hassle of writing it all from scratch.

Embedding HornetQ can be done in very few easy steps. Instantiate the configuration object, instantiate the server, start it, and you have a HornetQ running in your virtual machine. It's as simple and easy as that.

## 43.1. Simple Config File Embedding

The simplest way to embed HornetQ is to use the embedded wrapper classes and configure HornetQ through its configuration files. There are two different helper classes for this depending on whether your using the HornetQ Core API or JMS.

### 43.1.1. Core API Only

For instantiating a core HornetQ Server only, the steps are pretty simple. The example requires that you have defined a configuration file `hornetq-configuration.xml` in your classpath:

    import org.hornetq.core.server.embedded.EmbeddedHornetQ;

    ...

    EmbeddedHornetQ embedded = new EmbeddedHornetQ();
    embedded.start();

    ClientSessionFactory nettyFactory =  HornetQClient.createClientSessionFactory(
                                            new TransportConfiguration(
                                               InVMConnectorFactory.class.getName()));

    ClientSession session = factory.createSession();

    session.createQueue("example", "example", true);

    ClientProducer producer = session.createProducer("example");

    ClientMessage message = session.createMessage(true);

    message.getBody().writeString("Hello");

    producer.send(message);

    session.start();

    ClientConsumer consumer = session.createConsumer("example");

    ClientMessage msgReceived = consumer.receive();

    System.out.println("message = " + msgReceived.getBody().readString());

    session.close();

`The `EmbeddedHornetQ` class has a few additional setter methods that allow you to specify a different config file name as well as other properties. See the javadocs for this class for more details.`

### 43.1.2. JMS API

JMS embedding is simple as well. This example requires that you have defined the config files `hornetq-configuration.xml`, `hornetq-jms.xml`, and a `hornetq-users.xml` if you have security enabled. Let's also assume that a queue and connection factory has been defined in the `hornetq-jms.xml` config file.

    import org.hornetq.jms.server.embedded.EmbeddedJMS;

    ...

    EmbeddedJMS jms = new EmbeddedJMS();
    jms.start();

    // This assumes we have configured hornetq-jms.xml with the appropriate config information
    ConnectionFactory connectionFactory = jms.lookup("ConnectionFactory");
    Destination destination = jms.lookup("/example/queue");

    ... regular JMS code ...

`By default, the `EmbeddedJMS` class will store component entries defined within your `hornetq-jms.xml` file in an internal concurrent hash map. The `EmbeddedJMS.lookup()` method returns components stored in this map. If you want to use JNDI, call the `EmbeddedJMS.setContext()` method with the root JNDI context you want your components bound into. See the javadocs for this class for more details on other config options.`

## 43.2. POJO instantiation - Embedding Programmatically

You can follow this step-by-step guide to programmatically embed the core, non-JMS HornetQ Server instance:

Create the configuration object - this contains configuration information for a HornetQ instance. The setter methods of this class allow you to programmitcally set configuration options as describe in the Section 48.1, “Server Configuration” section.

The acceptors are configured through `ConfigurationImpl`. Just add the `NettyAcceptorFactory` on the transports the same way you would through the main configuration file.

    import org.hornetq.core.config.Configuration;
    import org.hornetq.core.config.impl.ConfigurationImpl;

    ...

    Configuration config = new ConfigurationImpl();
    HashSet<TransportConfiguration> transports = new HashSet<TransportConfiguration>();

    transports.add(new TransportConfiguration(NettyAcceptorFactory.class.getName()));
    transports.add(new TransportConfiguration(InVMAcceptorFactory.class.getName()));

    config.setAcceptorConfigurations(transports);

You need to instantiate an instance of `org.hornetq.api.core.server.embedded.EmbeddedHornetQ` and add the configuration object to it.

    import org.hornetq.api.core.server.HornetQ;
    import org.hornetq.core.server.embedded.EmbeddedHornetQ;

    ...

    EmbeddedHornetQ server = new EmbeddedHornetQ();
    server.setConfiguration(config);

    server.start();

You also have the option of instantiating `HornetQServerImpl` directly:

    HornetQServer server =
            new HornetQServerImpl(config);
    server.start();

For JMS POJO instantiation, you work with the EmbeddedJMS class instead as described earlier. First you define the configuration programmatically for your ConnectionFactory and Destination objects, then set the JmsConfiguration property of the EmbeddedJMS class. Here is an example of this:

    // Step 1. Create HornetQ core configuration, and set the properties accordingly
    Configuration configuration = new ConfigurationImpl();
    configuration.setPersistenceEnabled(false);
    configuration.setSecurityEnabled(false);
    configuration.getAcceptorConfigurations()
             .add(new TransportConfiguration(NettyAcceptorFactory.class.getName()));

    // Step 2. Create the JMS configuration
    JMSConfiguration jmsConfig = new JMSConfigurationImpl();

    // Step 3. Configure the JMS ConnectionFactory
    TransportConfiguration connectorConfig = new TransportConfiguration(NettyConnectorFactory.class.getName());
    ConnectionFactoryConfiguration cfConfig = new ConnectionFactoryConfigurationImpl("cf", connectorConfig, "/cf");
    jmsConfig.getConnectionFactoryConfigurations().add(cfConfig);

    // Step 4. Configure the JMS Queue
    JMSQueueConfiguration queueConfig = new JMSQueueConfigurationImpl("queue1", null, false, "/queue/queue1");
    jmsConfig.getQueueConfigurations().add(queueConfig);

    // Step 5. Start the JMS Server using the HornetQ core server and the JMS configuration
    EmbeddedJMS jmsServer = new EmbeddedJMS();
    jmsServer.setConfiguration(configuration);
    jmsServer.setJmsConfiguration(jmsConfig);
    jmsServer.start();

Please see Section 11.1.19, “Embedded” for an example which shows how to setup and run HornetQ embedded with JMS.

## 43.3. Dependency Frameworks

You may also choose to use a dependency injection framework such as JBoss Micro Container™ or Spring Framework™. See Chapter 44, Spring Integration for more details on Spring and HornetQ, but here's how you would do things with the JBoss Micro Contaier.

HornetQ standalone uses JBoss Micro Container as the injection framework. `HornetQBootstrapServer` and `hornetq-beans.xml` which are part of the HornetQ distribution provide a very complete implementation of what's needed to bootstrap the server using JBoss Micro Container.

When using JBoss Micro Container, you need to provide an XML file declaring the `HornetQServer` and `Configuration` object, you can also inject a security manager and a MBean server if you want, but those are optional.

A very basic XML Bean declaration for the JBoss Micro Container would be:

    <?xml version="1.0" encoding="UTF-8"?>

    <deployment xmlns="urn:jboss:bean-deployer:2.0">

       <!-- The core configuration -->
       <bean name="Configuration"
             class="org.hornetq.core.config.impl.FileConfiguration">
       </bean>

       	<!-- The core server -->
       <bean name="HornetQServer"
             class="org.hornetq.core.server.impl.HornetQServerImpl">
          <constructor>
             <parameter>
                <inject bean="Configuration"/>
             </parameter>
          </constructor>
       </bean>
       </deployment>

`HornetQBootstrapServer` provides an easy encapsulation of JBoss Micro Container.

    HornetQBootstrapServer bootStrap =
            new HornetQBootstrapServer(new String[] {"hornetq-beans.xml"});
            bootStrap.run(

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