Talk at ZEUS 2009 about rich data manipulation in BPEL using E4X.

1. Facilitating Rich Data Manipulation in BPEL
using E4X
Tammo van Lessen, Jörg Nitzsche, Dimka Karastoyanova
Institute of Architecture of Application Systems
(IAAS)
University of Stuttgart
Universitätsstr. 38
70569 Stuttgart
Germany
tammo.van.lessen@iaas.uni‐stuttgart.de

2. The Talk Today
Motivation and Introduction
Combining WS‐BPEL with E4X
Extension Assign Operation & Extension Activity
Injecting BPEL variables
Built‐in functions
Conclusions
© Tammo van Lessen 2

3. Problem Statement
Business Analyst
Process Developer
© Tammo van Lessen 3

4. Low‐level Problems
BPEL Variables must be initialized var TShoppingCart shoppingCart
var TItem item
var EItem eitem
Data types are typically not aligned
Create
Data mediation required Shopping
selectionFailure Cart
Array manipulation is cumbersome
doXSLTransform AddItem Complete
Custom XSL scripts needed
Data type Check Submit
Reuse not possible mismatch Availability Order
Add to
Confirm
doXSLTransform Cart
© Tammo van Lessen 4

5. Alternatives
BPELJ
Use plain old Java snippets
Pro: Easy to use
Con: W3C DOM still quite cumbersome
Semantic Data Mediation
SUPER technology
Pro: Killer feature on the conceptual level
Con: Requires too much modelling efforts
<s:mediate inputVariable=quot;xquot; outputVariable=quot;yquot; mediatorIRI=quot;urn:anyquot;? />
© Tammo van Lessen 5

6. What is JavaScript/E4X?
JavaScript
ECMA 262, Edition 3
JavaScript 1.6
E4X
Proposed by BEA
ECMA 357
XML support at the language level
Literals, nodes, attributes, namespaces…
XPath‐like syntax
foreach…
Allows nodesets as LHS expressions
var items = <items>
<item name=quot;SOA bookquot; price=quot;40quot; quantity=quot;2quot;/>
<item name=quot;BPM bookquot; price=quot;35quot; quantity=quot;3quot;/>
<item name=quot;EAI bookquot; price=quot;30quot; quantity=quot;1quot;/>
</items>;
alert( items.item.(@name == quot;SOA bookquot;).@quantity );
for each( var thisPrice in items..@price ) {
sum += thisPrice;
}
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© Tammo van Lessen

7. Using Javascript/E4X in BPEL <assign>
<assign name=quot;e4x-assignquot;>
<extensionAssignOperation>
<js:snippet>
myVar.TestPart += ' World';
</js:snippet>
</extensionAssignOperation>
</assign>
<assign name=quot;e4x-array-assignquot;>
<extensionAssignOperation>
<js:snippet>
load('shoppingCartUtils.js');
shoppingCart.parameters = createShoppingCartSkeleton();
shoppingCart.parameters.items += createCartItem(item);
shoppingCart.parameters.items.item.(@hyped=='true').price *= 2;
</js:snippet>
</extensionAssignOperation>
</assign>
BPEL variables are injected into JS context
Variables can be read and written
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© Tammo van Lessen

8. Using Javascript/E4X in BPEL <extensionActivities>
<extensionActivity name=“adjustShippingDetailsquot;>
<js:snippet>
if (goldRatio > 1.0 || silverRatio > 1.0) {
throwFault('urn:myprocess', 'IllegalArgumentFault',
'discount ratios must be <= 1.0');
}
if (customer.type == 'gold') {
po.items.item.price *= goldRatio;
} else if (customer.type == 'silver') {
po.items.item.price *= silverRatio;
} else if (customer.type == 'besteffort') {
po.shippingMode = 'snailmail';
}
</js:snippet>
</extensionActivity>
JavaScript functions can be used to reuse such
snippets
Use with caution!
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© Tammo van Lessen

9. Built‐in Functions
load(…)
Loads custom JS/E4X library
print(…)
Prints debug output to console
piid()
Returns process instance ID
activityName()
Returns activity name
processName()
Returns the process’ QName
throwFault(namespace, localpart, faultmsg)
throwFault(xmlobject)
Throws a BPEL fault
validate(…)
Validates a variable’s content against its schema
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© Tammo van Lessen

10. Conclusions
Variable Assignments in vanilla BPEL are cumbersome
Adding items to lists is not possible
Would require a nodeset as LHS expression
Can be done using external XSL scripts
Batch‐updating an XPath match is not possible
Variable initialization is very verbose
No reuse possible for recurring data manipulation tasks.
Using E4X in BPEL
Provides a convenient syntax for rich XML manipulation
Reuse of such scripts across activities and processes is possible
Simplifies array manipulation
Implementation available
Publicly available in Apache ODE
Will be part of the upcoming 2.0 release
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© Tammo van Lessen

11. End of Document