Feature

The POJO (Plain Old Java Object) component is a Service Engine (SE) which allows to expose your own Java classes as Services. It is useful to refactor your own Business logic as services.
Each POJO service is represented by a provides section in a POJO Service Unit.
This component provides only services and doesn't act as a consumer of service.
This component is based on the PEtALS CDK.

Exposing a Java class as a POJO service

PROVIDE SERVICE : Expose a Java class as a Service

Usage

A Java class acting as a POJO service must follow these rules :

• no specific interface implementation is required.
• if a public setComponentContext(ComponentContext context) setter method is defined, the component set its ComponentContext instance with this method at the initialization of the POJO.
• if a public setDeliveryChannel(DeliveryChannel channel) setter method is defined, the component set its DeliveryChannel instance with this method at the initialization of the POJO.
• if a public setJBIListener(AbstractJBIListener jbiListener) setter method is defined, the component set its JBIListener instance with this method at the initialization of the POJO.
• if a public setLogger(Logger logger) setter method is defined, the component set its Logger instance with this
  method at the initialization of the POJO.
• if a public void init() method is defined, the compenent invoke it at the initialization of the POJO.
• a public boolean onExchange(Exchange exchange) MUST be provided.
• all methods can throw exceptions.

A sample class following those rules:

package test;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.jbi.component.ComponentContext;
import org.ow2.petals.component.framework.api.message.Exchange;
import org.ow2.petals.component.framework.listener.AbstractJBIListener;
public class SamplePojoService {
  AbstractJBIListener jbiListener;
  Logger logger;
  ComponentContext ctx;
  public void setJBIListener(AbstractJBIListener jbiListener) {
    this.jbiListener = jbiListener;
  }
  public void setComponentContext(ComponentContext ctx) {
    this.ctx = ctx;
  }
  public void setLogger(Logger logger) {
    this.logger = logger;
  }
  public boolean onExchange(Exchange exchange)
    throws Exception {
    [...]
    jbiListener.sendSync(anotherExchange);
    [...]
    return false;
  }
  public void init() {
    logger.log(Level.INFO, "SamplePojo inits.");
  }
}

The method onExchange(Exchange exchange) is invoked when a MessageExchange targeting the POJO service is
received on the component. The POJO service must process the service here.
If the POJO service sets a response on the exchange to support patterns InOut or InOptionalOut, the method has to return true. The component will send the response back.
Otherwise, the method return false and the component responds with a DONE acknowledgement.
If an exception is raised, depending of the nature of the exception (RuntimeException , FaultException...) and the pattern, a Fault or an ERROR acknowledgement will be sent.

Configuration

Service Unit descriptor

The POJO class(es) and their depending libraries must be set in JAR(s) file(s) at the root directory of the POJO Service
Unit package.
The POJO JBI descriptor must contain a provides section for each POJO to expose in the JBI bus. For each provides
section, the name of the POJO class must be filled.
Here is an example:

<?xml version="1.0" encoding="UTF-8"?>
<!-- JBI descriptor for PEtALS' "petals-se-pojo" (POJO), version 2.0 -->
<jbi:jbi version="1.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:jbi="http://java.sun.com/xml/ns/jbi"
  xmlns:pojo="http://petals.ow2.org/components/pojo/version-2.0"
  xmlns:petalsCDK="http://petals.ow2.org/components/extensions/version-4.0"
  xmlns:generatedNs="http://POJO/test">
  <!-- Import a Service into PEtALS or Expose a PEtALS Service => use a BC. -->
  <jbi:services binding-component="false">
     <!-- Import a Service into PEtALS => provides a Service. -->
     <jbi:provides
       interface-name="generatedNs:POJO"
       service-name="generatedNs:POJOService"
       endpoint-name="POJOServiceEndpoint">
       <!-- CDK specific elements -->
       <petalsCDK:wsdl xsi:nil="true" />
       <!-- Component specific elements -->
       <pojo:class-name>test.SamplePojoService</pojo:class-name>
     </jbi:provides>
  </jbi:services>
</jbi:jbi>

Service Unit content

The Service Unit has to contain the following elements, packaged in an archive:

• The META-INF/jbi.xml descriptor file, has described above.
• At least one jar containing the POJO class to expose

  service-unit.zip
  + META-INF
           - jbi.xml (as defined above)
           - mypojoclasses.jar
  

Component Configuration

The following attributes can be set during the installation phase to configure the component, using the params element of the jbi-install-component ANT task:

Parameter	Description	Default	Required	Required
acceptor-pool-size	The size of the thread pool used to accept Message Exchanges from the NMR. Once a message is accepted, its processing is delegated to the processor pool thread.	3	Yes	Runtime
processor-pool-size	The size of the thread pool used to process Message Exchanges. Once a message is accepted, its processing is delegated to one of the thread of this pool.	10	Yes	Runtime
ignored-status	When the component receives an acknowledgement message exchange, it can skip the processing of these message according to the type of the acknowledgment. If you decide to not ignore some acknowledgement, the component listeners must take care of them. Accepted values : DONE_AND_ERROR_IGNORED, DONE_IGNORED, ERROR_IGNORED or NOTHING_IGNORED	DONE_AND_ERROR_IGNORED	Yes	Component
properties-file	Name of the file containing properties used as reference by other parameters. Parameters reference the property name in the following pattern ${myPropertyName}. At runtime, the expression is replaced by the value of the property. The value of this parameter is : an URL a file relative to the PEtALS installation path an empty value to stipulate a non-using file	-	No	Installation
external-listener-class-name	Qualified name of the class extending AbstractExternalListener Only for Binding Components	-	No	Component
jbi-listener-class-name	Qualified name of the class extending AbstractJBIListener	-	Yes	Component
performance-notifications	Enable the performance notifications in the component. The CDK proposes to a performance notification feature to the component implementor. If you enable this feature, you must use the related method accessible in the AbstractComponent class.	-	No	Runtime
performance-step	When the performance notification feature is enabled, it is possible to define a step on the notifications. When there is an heavy message traffic, it is recommanded to increase this step to avoid performance disturbance.	-	No	Runtime

Definition of CDK parameter scope :

• Component : The parameter has been defined during the development of the component. A user of the component can not change its value.
• Installation: The parameter can be set during the installation of the component, by using the installation MBean (see JBI specifications for details about the installation sequence). If the parameter is optional and has not been defined during the development of the component, it is not available at installation time.
• Runtime : The paramater can be set during the installation of the component and during runtime. The runtime configuration can be changed using the CDK custom MBean named RuntimeConfiguration. If the parameter is optional and has not been defined during the development of the component, it is not available at installation and runtime times.