• Introducing JBI
  • What is JBI?
  • JBI MEPs
  • JBI API
• JBI Components
  • servicemix-bean
  • servicemix-camel
  • servicemix-cxf-bc
  • servicemix-cxf-se
  • servicemix-drools
  • servicemix-eip
  • servicemix-exec
  • servicemix-file
  • servicemix-ftp
  • servicemix-http
  • servicemix-jms
  • servicemix-mail
  • servicemix-osworkflow
  • servicemix-quartz
  • servicemix-saxon
  • servicemix-scripting
  • servicemix-snmp
  • servicemix-validation
  • servicemix-vfs
  • servicemix-wsn2005
  • servicemix-xmpp

servicemix-bean

Overview

The ServiceMix Bean component provides integration with beans (POJOs) with the JBI bus to make it easy to use POJOs to process JBI message exchanges. Like in an Message Driven Bean in J2EE a POJO will receive a message from the NMR and process it in any way it likes. Unlike in a JMS component where the coding is already done the Bean component gives the developer the freedom to create any type of message handling but it must be hand coded all the way.

Namespace and xbean.xml

The namespace URI for the servicemix-bean JBI component is http://servicemix.apache.org/bean/1.0. This is an example of an xbean.xml file with a namespace definition with prefix bean.

<beans xmlns:bean="http://servicemix.apache.org/bean/1.0">
  <bean:endpoint service="test:service" endpoint="endpoint" bean="#listenerBean"/>
  <bean id="listenerBean" class="org.apache.servicemix.bean.beans.ListenerBean"/>
</beans></beans>

Endpoint types

The servicemix-bean component only defines one endpoint, called bean:endpoint. It can be used to receive and send message exchanges from/to the NMR.

Endpoint bean:endpoint

There are two ways to configure the bean endpoint. The first is using the fully qualified name of the class and the second is by passing to the endpoint a reference to an existing bean.

Using a Java class

When definining a bean:endpoint specifying a Java class name, a new instance of this class will be created for handling a single message exchange.

<beans xmlns:bean="http://servicemix.apache.org/bean/1.0"
       xmlns:my="urn:org:servicmix:docs:examples">

  <bean:endpoint service="my:service" endpoint="endpoint"
                 class="org.apache.servicemix.docs.bean.MyHandlerBean"/>

</beans>

Using a spring bean

Alternative, a reference to an existing bean can be passed to the bean endpoint.

<beans xmlns:bean="http://servicemix.apache.org/bean/1.0">
    <bean:endpoint service="test:service" endpoint="endpoint" bean="#listenerBean"/>
    <bean id="listenerBean" class="org.apache.servicemix.bean.beans.ListenerBean"/>
</beans>

Attention: The Bean Endpoint schema allows to set a Bean or a Bean Name. The Bean will create a single instance of the POJO per endpoint whereas the Bean Name will create an instance per request (message exchange).

Endpoint properties

MessageExchangeListener

The first kind of POJOs you can deploy implement the MessageExchagneListener interface. In such a case, servicemix-bean acts as a replacement of the lightweight container component. This level offers the most control on the exchange received and sent. This is usually used with the injected DeliveryChannel to send back the exchanges, or if the POJOs needs to act as a consumer (i.e. creating and sending exchanges to other services).

These POJOs are low-level POJOs: you need to understand the JBI Api and Message Exchange Patterns to correctly handle incoming exchanges.

Note that at this point (v 3.1), there is no base class that you can inherit to speed you in this process of implementing a POJO to handle JBI exchanges, but hopefully it will come in the future.

Examples

This example on the right shows the most simple bean. When it receives an exchange, it will print it to the console and set the status to DONE before sending the exchange back. This bean can not handle InOut exchanges, as it does not set any response (an exception would be thrown in such a case).

import org.apache.servicemix.jbi.listener.MessageExchangeListener;

import javax.annotation.Resource;
import javax.jbi.messaging.DeliveryChannel;
import javax.jbi.messaging.ExchangeStatus;
import javax.jbi.messaging.MessageExchange;
import javax.jbi.messaging.MessagingException;

public class ListenerBean implements MessageExchangeListener {

    @Resource
    private DeliveryChannel channel;

    public void onMessageExchange(MessageExchange exchange) throws MessagingException {
        System.out.println("Received exchange: " + exchange);
        exchange.setStatus(ExchangeStatus.DONE);
        channel.send(exchange);
    }

}

This example will handle an InOut exchange and will send back the input as the response.
Note that this example would fail if receiving an InOnly exchange, as setting a response on an InOnly exchange is not a legal operation.

import org.apache.servicemix.jbi.listener.MessageExchangeListener;
import org.apache.servicemix.jbi.util.MessageUtil;

import javax.annotation.Resource;
import javax.jbi.messaging.DeliveryChannel;
import javax.jbi.messaging.ExchangeStatus;
import javax.jbi.messaging.MessageExchange;
import javax.jbi.messaging.MessagingException;

public class ListenerBean implements MessageExchangeListener {

    @Resource
    private DeliveryChannel channel;

    public void onMessageExchange(MessageExchange exchange) throws MessagingException {
        if (exchange.getStatus() == ExchangeStatus.ACTIVE) {
            MessageUtil.transferInToOut(exchange, exchange);
            channel.send(exchange);
        }
    }

}

This is similar example as the one from above (also works only for InOut exchange) but it shows how you can extract message from an exchange in order to process it and send back.

import org.apache.servicemix.jbi.listener.MessageExchangeListener;
import org.apache.servicemix.jbi.util.MessageUtil;
import org.apache.servicemix.jbi.jaxp.SourceTransformer;

import javax.annotation.Resource;
import javax.jbi.messaging.DeliveryChannel;
import javax.jbi.messaging.ExchangeStatus;
import javax.jbi.messaging.MessageExchange;
import javax.jbi.messaging.MessagingException;
import javax.jbi.messaging.NormalizedMessage;
import javax.xml.transform.Source;

public class ListenerBean implements MessageExchangeListener {

    @Resource
    private DeliveryChannel channel;

    public void onMessageExchange(MessageExchange exchange) throws MessagingException {
        if (exchange.getStatus() == ExchangeStatus.ACTIVE) {
                        NormalizedMessage message = exchange.getMessage("in");
		        Source content = message.getContent();
			//process content according to your logic
			//e.g. to access the message body as a String use
			String body = (new SourceTransformer()).toString(content);

			message.setContent(content);
			exchange.setMessage(message, "out");
			channel.send(exchange);
        }
    }

}

Disclaimer

In versions 3.1 to 3.1.2 the ServiceMix Bean component will not handle asynchronous messages correctly because the final send of the message marked as DONE back to the NMR will be handled as a consumer message and that fails because there is no corresponding provider message. The only workaround is to send the messages synchronously.

Note: This was resolved in 3.1.3, 3.2.x and later via SM-1110.

MessageExchange dispatching

If the POJO deployed implements the org.apache.servicemix.MessageExchangeListener, every message received for this POJO will be dispatched to the onMessageExchange method.

In other cases, exchanges in a provider role will be dispatched according to the MethodInvocationStrategy configured on the endpoint. The default one try to find the method according to the operation name defined on the exchange. If there is only a single method acting as an operation, it will always be used.

Annotations

The servicemix-bean component can accept different kind of POJOs. These POJOs may be annotated to customize their behavior. All the following annotations belong to the org.apache.servicemix.bean package.

In addition, standard annotations can be used:

The following interfaces are part of this API:

More Examples

• AnnotatedBean

• AutoDeployedBean

• ConsumerBean

• ListenerBean

• PlainBean