BPEL Example Ja

Overview of the ServiceMix 1.x BPEL Example

This document describes how to run ServiceMix's BPEL example and provides details about what it does. For information on the business use case, please refer to: Use Case for BPEL.

The BPEL example illustrates the following:

• an example of declarative programming
• how to perform BPEL integration with ServiceMix

The XML code for the BPEL example is located in the ServiceMix installation directory under the examples\bpel directory in the servicemix.xml file. It is recommended that you refer to the servicemix.xml file while reading this document.

This example will start a component which sends a SOAP message to a JmsServiceComponent which forwards the request to the PXE BPEL engine and waits for a response. A simple JMS client is provided so that messages can sent and received from the JMSService. This example uses PXE integration to demonstrate the use of BPEL with ServiceMix.

Prerequisites to Run the BPEL Example

The following must be installed to run this example:

• Java Standard Edition 5.0
• Ant - http://ant.apache.org.
• PXE - We support WS-BPEL via the PXE BPEL Engine from FiveSight.

Running the BPEL Example

First, run ServiceMix with a JNDI context configured so that PXE can be deployed.

PXE has a JBI component and deployment unit which, thanks to JBI, can just auto-deploy in any JBI compliant container. So the easiest way to use PXE right now with ServiceMix is to just drop the PXE deployment unit into the install directory in the binary ServiceMix distribution and the component will be auto-deployed in ServiceMix. Look in the install directory under the servicemix_install_dir\examples\bpel directory to see PXE jar file.

From a command shell, go to the BPEL example directory:

cd [servicemix_install_dir]\examples\bpel

where servicemix_install_dir is the directory in which ServiceMix was installed.

Then type:

[servicemix_install_dir]\bin\servicemix servicemix.xml

OR

..\..\bin\servicemix servicemix.xml

You should now have PXE deployed with a JBI service engine together with a deployment unit for a specific BPEL process.

Send the business process messages to trigger it. Compile and run a simple JMS client. The client is built and run from source using Ant. Execute 'ant from BPEL's directory, servicemix_install_dir\examples\bpel to run the JMS client:

ant

Ant will compile and run the simple JMS client which performs a JMS based request-response into the ServiceMix container before returning the results to the console.

Stopping the BPEL Example

To terminate the BPEL example type "CTRL-C" in the command shell in which it is running and answer "y" to the "Terminate batch job (y/n)?" question.

How it Works

The diagram below illustrates the logical flow of the program through the BPEL components.

The logical flow of the program is:

1. myComponent subscribes to the "demo.org.servicemix.source" topic. Through its template property, myComponent uses JmsFactory to listen on
   port 61616 via ActiveMQConnectionFactory.
2. When JMSClient is executed, it tries to make a connection to the topic demo.org.servicemix.source at port 61616
3. It then send a text message through this connection and waits for a response.
4. myComponent receives the message and transmit it to ProcessSVC which is probably the BPEL engine as specified in the destinationService
   property in the servicemix.xml file.
5. When the transmission is successful myComponent send a reply to the JMSClient and "Response was @response" is printed on the console.
   Otherwise "Response time out" is printed.

Logginginformation is written to the console as files are transmitted. Typical output looks like the following:

 
 
ServiceMix ESB: 1.0.1

Loading ServiceMix from file: servicemix.xml
[INFO] XmlBeanDefinitionReader - -Loading XML bean definitions from file [C:\Program Files\servicemix-1.0.1\examples\file-binding\servicemi.xml]
[INFO] FileSystemXmlApplicationContext - -Bean factory for application context [org.springframework.context.support.FileSystemXmlApplication
Context;hashCode=7486844]: org.springframework.beans.factory.support.DefaultListableBeanFactory defining beans [workManager,jbi]; root of BeanFactory hierarchy
[INFO] FileSystemXmlApplicationContext - -2 beans defined in application context 
[org.springframework.context.support.FileSystemXmlApplicationContext;hashCode=7486844]
[INFO] CollectionFactory - -JDK 1.4+ collections available
[INFO] CollectionFactory - -Commons Collections 3.x available
[INFO] FileSystemXmlApplicationContext - -Unable to locate MessageSource with name 'messageSource': using default [org.springframework.conte
xt.support.DelegatingMessageSource@1d6776d]
[INFO] FileSystemXmlApplicationContext - -Unable to locate ApplicationEventMulticaster with name 'applicationEventMulticaster': using defaul
t [org.springframework.context.event.SimpleApplicationEventMulticaster@4fce71]
[INFO] DefaultListableBeanFactory - -Pre-instantiating singletons in factory [org.springframework.beans.factory.support.DefaultListableBeanF
actory defining beans [workManager,jbi]; root of BeanFactory hierarchy]
[INFO] DefaultListableBeanFactory - -Creating shared instance of singleton bean 'workManager'
[INFO] DefaultListableBeanFactory - -Creating shared instance of singleton bean 'jbi'
Created MBeanServer with ID: 203c31:106bd250a5b:-7fff:Lisas:1
[INFO] SpringInitialContextFactory - -Loading JNDI context from: class path resource [jndi.xml]
[INFO] XmlBeanDefinitionReader - -Loading XML bean definitions from class path resource [jndi.xml]
[INFO] XmlBeanFactory - -Creating shared instance of singleton bean 'jndi'
RMIConnectorServer started at: service:jmx:rmi://lisas/jndi/rmi://localhost:1099/defaultJBIJMX
[INFO] JBIContainer - -ServiceMix JBI Container (http://servicemix.org/) name: defaultJBI running version: ServiceMix.
[INFO] JBIContainer - -Activating component for: [container=defaultJBI,name=fileSender,id=fileSender] with service: fileSender component: org.servicemix.components.file.FileWriter@b1cc87
[INFO] ComponentContextImpl - -Component: fileSender activated endpoint: fileSender : fileSender
[INFO] JBIContainer - -Activating component for: [container=defaultJBI,name=filePoller,id=filePoller] with service: filePoller component: or
g.servicemix.components.file.FilePoller@183e7de
[INFO] ComponentContextImpl - -Component: filePoller activated endpoint: filePoller : filePoller
[INFO] DeliveryChannel - -default destination serviceName for filePoller = fileSender

Note: In the servicemix.xml file, the "destinationService" attribute of the filePoller component is "foo:fileSender." The last line of output (above) shows the NMR using that to deliver the normalized message to fileSender.

Details

The following table provides more details about the function of each component and bean in the servicemix.xml file.

Useful Code Hints

This section describes the start-up sequence and how the ServiceMix container interacts with the BPEL application. The Java class files are located in the servicemix-1.0.1.jar file in the ServiceMix installation directory. To look at the Java source code, unjar and decompile the .class files or download the source code. Please note: the downloadable source code is slightly different than the compiled binary code.

Viewing the Java source code is recommended for understanding the information in this section.

filePoller Details

1. The ServiceMix container reads the servicemix.xml file and sees it needs to instantiate a FilePoller.
2. The container calls the init() method of FilePoller, as well as the init() methods of its parents.
3. The container determines that FilePoller is an MBean and, therefore, calls the start() method of FilePoller, which it inherits from its parent PollingComponentSupport.
4. The start() method will: (See: PollingComponentSupport.java code fragment below)
   A. Create a timerTask.
   B. Schedule the timerTask at a fixed rate. The start() method uses the "timer" (created in the init method) to schedule the timerTask at a fixed rate: timer.scheduleAtFixedRate(timerTask, firstTime, period). Recall "period" is a property of FilePoller. It was assigned the value of 1000ms by dependency injection from the servicemix.xml file.
   C. timer will call the run() method of the timerTask periodically. timerTask's run method() is defined inline. This run() method will get the workManager object (see below for details).
   D. The workManager will call "scheduleWork(PollingComponentSupport.this)". Note: it passes in PollingComponent support, which by virtue of its inheritance hierarchy, is of type "Work", which is a "Runnable" object.
   E. "workManager.scheduleWork(Work)" will get a Thread, passing in a Runnable object, i.e. PollingComponentSupport, and call its run() method.
   F. PollingComponent's run() method calls poll(), which is implemented in FilePoller.
   G. From this point on the call sequence can be followed in FilePoller...
   H. The start() method of PollingComponentSupport, will eventually call super.start(), which propagates up to call the start() method of BaseLifeCycle, which sets the component state to "RUNNING."

Eventually, one of the threads that is polling (see step G) for a file in the inbox directory will see a one. It will use workManager's thread pool to get a thread for processing the file. Processing the file consists of streaming it from inbox, creating a normalized message, and sending the message to the NMR.

  timerTask = new TimerTask() {
     public void run() {
          try {
                getWorkManager().scheduleWork(PollingComponentSupport.this);
          }
          catch (Throwable e) {
                log.error("Failed to schedule work: " + e, e);
          }
     }
  };
  if (firstTime != null) {
     timer.scheduleAtFixedRate(timerTask, firstTime, period);
  }
  else {
     timer.scheduleAtFixedRate(timerTask, delay, period);
  }
}
super.start();

workManager Details

workManager is a property of the FilePoller object. This property is defined by a local reference, the "ref" attribute in the servicemix.xml file. The local reference is a bean which instantiates org.activemq.work.SpringWorkManager.

The SpringWorkManager is a Spring bean. By default when a Spring bean starts, the properties are set, and then the afterPropertiesSet() method is called by the container.

The workManager is used to allocate threads. The FilePoller asks for threads from the workManager for two operations:

1. The timerTask uses threads from the thread pool to periodically check the inbox directory for files.
2. The workManager will also allocate a thread to process a file (read, normalize and send to NMR). The workManager calls a scheduleWork() method which is non-blocking. Therefore, if multiple files need to be processed, FilePoller can continue making requests to the workManager to schedule work.

Summarizing, when the ServiceMix container instantiates an MBean it firsts sets the property values if there are any, then calls the init() method of the class and its' parent classes, if applicable. Then it calls the start() method of the class. When a Spring bean starts up, the properties are set and then the afterPropertiesSet() method is called.

Related Documentation

For more information on the following topics please see:

• NMR

• Spring