Home arrow Web Services arrow Page 2 - Flow and Web Services
WEB SERVICES

Flow and Web Services


Last week, we looked at process lifecycles. This week, we'll take a look at the assign and other basic activities, and study flow. This article, the fourth in a series, is excerpted from chapter 12 of Building Web Services with Java: Making sense of XML, SOAP, WSDL, and UDDI, written by Steve Graham et al. (Sams; ISBN: 0672326418).

Author Info:
By: Sams Publishing
Rating: 4 stars4 stars4 stars4 stars4 stars / 5
August 24, 2006
TABLE OF CONTENTS:
  1. · Flow and Web Services
  2. · XPath Extension Functions
  3. · Flows
  4. · Link Semantics
  5. · Putting Together the Flow Sample

print this article
SEARCH DEVARTICLES

Flow and Web Services - XPath Extension Functions
(Page 2 of 5 )

Last but not least there is the need to access data from a process not only as part of assignments, but also to control the behavior of a process (for example, in conditions). In order to enable arbitrary XPath expressions to access data from the process, BPEL introduces several XPath extension functions.

The getVariableData function extracts arbitrary values from variables. The partName and locationPath arguments are optional:

getVariableData("variableName", "partName",
"locationPath")

A variable can carry global message properties, the values of which can be extracted using the getVariableProperty function with the qualified name of the global property:

getVariableProperty("variableName",
"propertyQName")

The getLinkStatus function returns a Boolean indicating the status of a link. It can only be applied in join conditions (see the section on links for details):

getLinkStatus("linkName") 

The extension functions are useful for all kinds of expressions: in transition conditions, join conditions, while conditions, and switch cases, as well as for duration and deadline expressions.

More Basic Activities: wait, empty

Let's briefly discuss the remaining two basic activities: wait and empty. The wait activity allows the business process to wait for a specific time interval (specified by a duration-valued XPath expression) or until a certain deadline is reached (specified by a deadline-valued XPath expression). The following wait activity waits until New Year's Eve:

<wait until="2004-12-31T18:00+1:00"/>

This wait activity waits for three days and 10 hours:

<wait for="P3DT10H"/>

The empty activity does nothing. It may, for example, be used as implementation of a fault handler if you need to catch and suppress a fault:

<empty/>

Next: Flows >>

blog comments powered by Disqus
WEB SERVICES ARTICLES

- Dealing with Loose Coupling in a Service-Ori...
- Loose Coupling in a Service-Oriented Archite...
- Safety, Idempotence, and the Resource-Orient...
- The Resource-Oriented Architecture in Action
- Features of the Resource-Oriented Architectu...
- The Resource-Oriented Architecture
- Getting Started with Flex
- Automated Billing and Faxing for the Web
- An Introduction to Web Services
- The Foundations of Web Services: From Novice...
- Web Services Reengineering: Finishing Touches
- Fault Handling with Web Services
- Flow and Web Services
- Process Lifecycles and Web Services
- Business Processes and Web Services

Watch our Tech Videos 
Dev Articles Forums 
 RSS  Articles
 RSS  Forums
 RSS  All Feeds
Write For Us 
Weekly Newsletter
 
Developer Updates  
Free Website Content 
Contact Us 
Site Map 
Privacy Policy 
Support 

Developer Shed Affiliates

 




© 2003-2017 by Developer Shed. All rights reserved. DS Cluster - Follow our Sitemap
Popular Web Development Topics
All Web Development Tutorials