bexee

bexee Administration package.

bexee Ant Tasks.

Axis integration package.

Core classes and interfaces of the bexee engine.

Persistence package; a "Data Access Object" pattern implementation for bexee.

A package with classes for simplyfied usage of the org.apache.ecs library.

bexee Event package.

Java representation of the BPEL language.

This package contains all interfaces representing BPEL activities as specified in the bpel4ws.xsd XML Schema.
While bexee provides a default implementation of those activity interfaces, it is possible to implement Activitites using an other technique.

BPEL activities can be subdivided in two groups, atomic activities and structured activities. Basic activities represent a functionality, e.g. calling an external service or receiving a call. Structured activities contain other atomic or structured activities.

This package contains default implementations of the interfaces from the bexee.model.activity package.

This package contains all interfaces representing BPEL elements as specified in the bpel4ws.xsd XML Schema.
While bexee provides a default implementation of those elements interfaces, it is possible to implement elements using an other technique.

This package contains default implementations of the interfaces from the bexee.model.elements package.

This package contains all interfaces representing BPEL expressions as specified in the bpel4ws.xsd XML Schema.
While bexee provides a default implementation of those expressions, it is possible to implement them using an other technique.

This package contains default implementations of the interfaces from the bexee.model.expression package.

This package contains interface which are used in order to represent a BPEL process. You can find the BPEL process specification in this bpel4ws.xsd XML schema.

This package contains default implementations for the bexee.model.process package.

This package contains BPEL process element and activity factories used by the Digester.

BPEL document transformation (XML-OO mapping)

Rationale and description

A deployed BPEL document needs to be transformed in a tree structure of objects representing a BPEL process type. Bexee will then use such a tree structure for the execution of processes. This transformation is a XML to OO mapping and within bexee this task is accomplished with the Jakarta Digester tool http://jakarta.apache.org/commons/digester/.

Briefly, the Digester is configured with an xml mapping description which describes how xml elements contained in BPEL documents will be mapped to the correspondent BPEL activities and elements. For the creation of activity, Digester is configured to use factories. Each activity type has its own specialized factory. In the following showing the usage of Digester and the creation of BPEL process types, this mapping description is called "bpel-rules.xml".

It is possible to let Digester create the objects without using specialized factories, but in the case of bexee it is advantageous to use this customized technique. BPEL activities have complex properties and it is easier to create those properties with specialized factories. In addition, BPEL activities and elements reference other elements, e.g. variables from the same BPEL process type. It is therefore necessary to find other elements (variables, partner links, etc.) and associate them with some activities in the BPEL process.

In order to be able to find other elements and activities existing in a BPEL process type, the factories used by Digester don't create process elements themselves, but delegate this task to a BPELElementFactory. Such a factory exist once per BPEL process, therefore all specialized activity and element factories used by Digester use the same BPELElementFactory, which exists once per BPEL process type. Every process element is registered at creation and can thus be found once referenced in an activity at a later time of BPEL document parsing.

Code and configuration excerpts

Following an excerpt from the Digester xml-oo mapping description "bpel-rules.xml"

          
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE digester-rules SYSTEM "http://bexee.sourceforge.net/dtd/digester-rules.dtd">
<digester-rules>
  <!--  -->
  <!-- parsing the Process -->
  <!--  -->

  <pattern value="process">
    <factory-create-rule classname="bexee.model.xmltobpel.ProcessImplFactory"/>
    <!--  -->
    <!-- parsing the PartnerLinks -->
    <!--  -->
    <pattern value="partnerLinks">

      <object-create-rule classname="bexee.model.elements.impl.PartnerLinksImpl"/>
      <pattern value="partnerLink">
        <factory-create-rule classname="bexee.model.xmltobpel.PartnerLinkImplFactory"/>
        <set-next-rule methodname="addPartnerLink"/>
      </pattern>
      <set-next-rule methodname="setPartnerLinks"/>

    </pattern>
    <!--  -->
    <!-- parsing the Variables -->
    <!--  -->
    <pattern value="variables">
      <object-create-rule classname="bexee.model.elements.impl.VariablesImpl"/>

      <pattern value="variable">
        <factory-create-rule classname="bexee.model.xmltobpel.VariableImplFactory"/>
        <set-next-rule methodname="addVariable"/>
      </pattern>
      <set-next-rule methodname="setVariables"/>
    </pattern>

  <set-next-rule methodname="setProcess"/>
  </pattern>
  <!--  -->
  <!-- parsing the sequence -->
  <!--  -->
  <pattern value="*/sequence">

    <object-create-rule classname="bexee.model.activity.impl.SequenceImpl"/>
    <set-properties-rule />
    <set-next-rule methodname="activity"/>
  </pattern>
  <!--  -->
  <!-- parsing receive -->

  <!--  -->
  <pattern value="*/receive">
    <factory-create-rule classname="bexee.model.xmltobpel.ReceiveImplFactory"/>
    <set-next-rule methodname="activity"/>
  </pattern>
  <!--  -->

  <!-- parsing invoke -->
  <!--  -->
  <pattern value="*/invoke">
    <factory-create-rule classname="bexee.model.xmltobpel.InvokeImplFactory"/>
    <set-next-rule methodname="activity"/>
  </pattern>

</digester-rules>
          

The java code for a factory responsible for the creation of a Receive BPEL activity:

"ReceiveImplFactory.java"

          
public class ReceiveImplFactory extends AbstractObjectCreationFactory {

    public Object createObject(Attributes attributes) throws Exception {

        BPELElementFactory elementFactory = BPELElementFactory
                .getInstance((BPELProcess) getDigester().getRoot());

        String partnerLink = attributes.getValue(PARTNER_LINK);
        String portType = attributes.getValue(PORT_TYPE);
        String operation = attributes.getValue(OPERATION);
        String variable = attributes.getValue(VARIABLE);
        String createInstance = attributes.getValue(CREATE_INSTANCE);

        return elementFactory.createReceive(getStandardAttributes(attributes),
                partnerLink, portType, operation, variable, createInstance);
    }
}
          

As already mentioned, the activity factory only delegates the creation of an Activity to the BPELElementFactory, following an excerpt from this element factory:

"BPELElementFactory.java"

          
public class BPELElementFactory {

    ...
    ...
    ...          
          
    private Map variables = new Hashtable();

    public Variable createVariable(String name, String messageType,
            String type, String element) {

        Variable variable = new VariableImpl();

        variable.setName(name);
        variable.setMessageType(expandToQName(messageType));
        variable.setType(expandToQName(type));
        variable.setElement(expandToQName(element));

        variables.put(name, variable);

        return variable;
    }
          
    public Object createReceive(StandardAttributes standardAttributes,
            String partnerLinkName, String portTypeString, String operation,
            String variableName, String createInstance) {

        PartnerLink partnerLink = retrievePartnerLink(partnerLinkName);
        QName portType = expandToQName(portTypeString);
        Variable variable = retrieveVariable(variableName);

        Receive receive = new ReceiveImpl(standardAttributes, partnerLink,
                portType, operation, variable, createInstance);

        return receive;
    }

    public Variable retrieveVariable(String variableName) {
        if (StringUtils.isNullOrEmpty(variableName)) {
            return null;
        }
        return (Variable) variables.get(variableName);
    }
    
    ...
    ...
    ...
          

bexee common utility classes.

bexee web interface package.

bexee WSDL extensions.

BPEL PartnerLinkType WSDL extension.

BPEL PartnerLinkType WSDL extension default implementation.