Feeds

Programming constructs in BPEL

Part 3: BPELJ and Compensation

Security and trust: The backbone of doing business over the internet

In this column in our series examining BPEL and its use within Service Oriented Architecture (SOA) systems, I'll will be looking at BPELJ and Compensation.

BPELJ is an extension to the core BPEL (Business Process Execution Language), which allows the direct inclusion of Java code within a BPEL script. Compensation is actually a core element of BPEL that provides an undo-like facility for situations where part of a BPEL script fails and other parts require their effects to be undone.

BPELJ

The aim of BPELJ is to let you embed Java and J2EE processes in a BPEL process. The intention is to allow portable integration of Java and J2EE applications into BPEL across application servers. In practice, most BPEL engines have allowed integration with programming languages such as Java in one form or another for some time, but via their own proprietary extensions. Thus, there have been BPEL extensions without portability, which I personally find extremely frustrating - because I need to support multiple application server environments.

BPELJ offers a glimmer of hope, in that it aims to provide a standard extension to BPEL for inline Java. The aim of BPELJ is to combine the power of a general purpose programming language such as Java with the orchestration and integration facilities of BPEL. By doing this, developers are free to select the appropriate "programming" language for the level of task they are implementing.

The Design of BPELJ

The design of BPELJ allows Java code to be embedded directly within a BPEL script in similar way to the embedding of Java within a JSP page. That is, BPELJ allows sections of Java code, called Java snippets, to be included in BPEL process definitions. Snippets are expressions or small blocks of Java code used for such things as loop conditions, branching conditions, variable initialisation, calling methods on Java objects etc.

Within BPEL standard extension points are used to support BPELJ. For example, a new partner link type is defined that references Java code; variables can now be typed as being of a specific Java class; and BPELJ code snippets can contain valid Java code statements, with the ability to invoke methods on Java classes from within BPEL statements.

BPELJ Examples

The following BPEL script illustrates the concepts presented in the above section. I've omitted much of this example for clarity, however, the core BPELJ elements remain:


<process name="BookCheck" 

expressionLanguage="http://jcp.org/java"

bpelj:package="com.regdev.example"

xmlns="http://schemas.xmlsoap.org/ws/2003/03/business-process/"

targetNamespace="http://regdev.com/bp/BookCheck"

xmlns:bpelj="http://schemas.xmlsoap.org/ws/2003/03/business-process/java"

xmlns:pq="http://regdev.com/ws/external/BookCheck">

<partnerLinks>

      ...

      <partnerLink name="lookup"  

              partnerLinkType="bpelj:com.regdev.BookLookup"/>

<variables>

   ....

   <variable name="message" type="bpelj:com.regdev.TextMessage"/>

</variables>

<sequence>

...

<flow>

...

</flow>

<bpelj:snippet name="Calculate Total">

   <bpelj:code>

      ...

      subtotal = subtotal * (1 – discount.getRate());

      response.setSubtotal(subtotal);

      float taxes = subtotal * taxRate;

      float total = subtotal + taxes;

      response.setTax(taxes);

      response.setTotal(total);

      ...

   </bpelj:code>

</bpelj:snippet>

...

<invoke partnerLink="BookLookup" operation="checkRegistration">

    <input part="Title" variable="title"/>

    <input part="ISBN" variable="isbn"/>

</invoke>

...

</sequence>

</process>

Providing a secure and efficient Helpdesk

Next page: Compensation

More from The Register

next story
New 'Cosmos' browser surfs the net by TXT alone
No data plan? No WiFi? No worries ... except sluggish download speed
'Windows 9' LEAK: Microsoft's playing catchup with Linux
Multiple desktops and live tiles in restored Start button star in new vids
iOS 8 release: WebGL now runs everywhere. Hurrah for 3D graphics!
HTML 5's pretty neat ... when your browser supports it
Mathematica hits the Web
Wolfram embraces the cloud, promies private cloud cut of its number-cruncher
Mozilla shutters Labs, tells nobody it's been dead for five months
Staffer's blog reveals all as projects languish on GitHub
'People have forgotten just how late the first iPhone arrived ...'
Plus: 'Google's IDEALISM is an injudicious justification for inappropriate biz practices'
SUSE Linux owner Attachmate gobbled by Micro Focus for $2.3bn
Merger will lead to mainframe and COBOL powerhouse
iOS 8 Healthkit gets a bug SO Apple KILLS it. That's real healthcare!
Not fit for purpose on day of launch, says Cupertino
prev story

Whitepapers

Secure remote control for conventional and virtual desktops
Balancing user privacy and privileged access, in accordance with compliance frameworks and legislation. Evaluating any potential remote control choice.
WIN a very cool portable ZX Spectrum
Win a one-off portable Spectrum built by legendary hardware hacker Ben Heck
Storage capacity and performance optimization at Mizuno USA
Mizuno USA turn to Tegile storage technology to solve both their SAN and backup issues.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
The next step in data security
With recent increased privacy concerns and computers becoming more powerful, the chance of hackers being able to crack smaller-sized RSA keys increases.