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Apache ODE – XPath Extensions

XPath Extensions

Overview

Apache ODE extends the default XPath coverage provided by the WS-BPEL specification mostly by adding support for XPath 2.0 and by offering a few utility extension functions to make some assignments easier.

XPath 2.0

To use XPath 2.0 in your processes just use the following queryLanguage and expressionLanguage attributes:

queryLanguage="urn:oasis:names:tc:wsbpel:2.0:sublang:xpath2.0"
expressionLanguage="urn:oasis:names:tc:wsbpel:2.0:sublang:xpath2.0"

If you want support at the process just add these attributes to your root process element. If you want to stick with XPath 1.0 but want XPath 2.0 support for a specific assignment you can also define these attributes on an assign element.

Extension Functions

All extension functions are defined in the ODE extension namespace: http://www.apache.org/ode/type/extension. This namespace will be associated with the ode prefix in the following examples.

insert-before

This is a function that allows you to insert one or more siblings (specified by the $siblings argument in the signature below) before the first node of children (specified by the $children argument), all of whose nodes must have the same parent (specified by the $context argument).

Insert Before
ode:insert-before($context as node(), $children as node()*, $siblings as node()*) as node()

By design, this function is non-updating in that it preserves the identity and properties of its arguments (i.e., they don't try to change the XML in-place). Instead, a modified copy of the context node is created, essentially giving it a new identity. Further, it returns a single R-value item, as opposed to a sequence. The example below illustrates how it may be used in the context of an assign activity:

<assign>
  <copy>
    <from>ode:insert-before($parent, $parent/child::node[position()=last()], $siblings)</from>
    <to variable="parent"/>
  </copy>
</assign>

For those familiar with the XQuery Update Facility, the above example is semantically equivalent to the expression shown below:

XQuery Equivalent
insert nodes $siblings before $parent/child::node[position()=last()]

insert-after

This is a function that allows you to insert one or more siblings (specified by the $siblings argument in the signature below) after the last node of children (specified by the $children argument), all of whose nodes must have the same parent (specified by the $context argument).

Insert After
ode:insert-after($context as node(), $children as node()*, $siblings as node()*) as node()

By design, this function is non-updating in that it preserves the identity and properties of its arguments (i.e., they don't try to change the XML in-place). Instead, a modified copy of the context node is created, essentially giving it a new identity. Further, it returns a single R-value item, as opposed to a sequence. The example below illustrates how it may be used in the context of an assign activity:

<assign>
  <copy>
    <from>ode:insert-after($parent, $parent/child::node(), $siblings)</from>
    <to variable="parent"/>
  </copy>
</assign>

For those familiar with the XQuery Update Facility, the above example is semantically equivalent to the expression shown below:

XQuery Equivalent
insert nodes $siblings after $parent/child::node()

insert-as-first-into

This is a function that allows you to insert the node(s) (specified by the $children argument in the signature below) as the first child(ren) of a given context node (specified by the $context argument).

Insert As First Into
ode:insert-as-first-into($context as node(), $children as node()*) as node()

By design, this function is non-updating in that it preserves the identity and properties of its arguments (i.e., they don't try to change the XML in-place). Instead, a modified copy of the context node is created, essentially giving it a new identity. Further, it returns a single R-value item, as opposed to a sequence. The example below illustrates how it may be used in the context of an assign activity:

<assign>
  <copy>
    <from>ode:insert-as-first-into($parent, $children)</from>
    <to variable="parent"/>
  </copy>
</assign>

For those familiar with the XQuery Update Facility, the above example is semantically equivalent to the expression shown below:

XQuery Equivalent
insert nodes $children as first into $parent

insert-as-last-into

This is a function that allows you to insert the node(s) (specified by the $children argument in the signature below) as the last child(ren) of a given context node (specified by the $context argument).

Insert As Last Into
ode:insert-as-last-into($context as node(), $children as node()*) as node()

By design, this function is non-updating in that it preserves the identity and properties of its arguments (i.e., they don't try to change the XML in-place). Instead, a modified copy of the context node is created, essentially giving it a new identity. Further, it returns a single R-value item, as opposed to a sequence. The example below illustrates how it may be used in the context of an assign activity:

<assign>
  <copy>
    <from>ode:insert-as-last-into($parent, $children)</from>
    <to variable="parent"/>
  </copy>
</assign>

For those familiar with the XQuery Update Facility, the above example is semantically equivalent to the expression shown below:

XQuery Equivalent
insert nodes $children as last into $parent

delete

This is a function that allows you to delete one or more node(s) (specified by the $children argument in the signature below) from its parent (specified by the $context argument).

Delete
ode:delete($context as node(), $children as node()*) as node()

By design, this function is non-updating in that it preserves the identity and properties of its arguments (i.e., they don't try to change the XML in-place). Instead, a modified copy of the context node is created, essentially giving it a new identity. Further, it returns a single R-value item, as opposed to a sequence. The example below illustrates how it may be used in the context of an assign activity:

<assign>
  <copy>
    <from>ode:delete($parent, $children)</from>
    <to variable="parent"/>
  </copy>
</assign>

For those familiar with the XQuery Update Facility, the above example is semantically equivalent to the expression shown below:

XQuery Equivalent
delete nodes $children

rename

This is a function that allows you to rename the context node (specified by the $context argument in the signature below) as per the given name (specified by $item, which is either a QName, Element or String).

Rename
ode:rename($context as node(), $name as item()) as node()

By design, this function is non-updating in that it preserves the identity and properties of its arguments (i.e., they don't try to change the XML in-place). Instead, a modified copy of the context node is created, essentially giving it a new identity. Further, it returns a single R-value item, as opposed to a sequence. The example below illustrates how it may be used in the context of an assign activity:

<assign>
  <copy>
    <from>ode:rename($person, fn:QName("http://www.example.com/example", "manager"))</from>
    <to variable="person"/>
  </copy>
</assign>

For those familiar with the XQuery Update Facility, the above example is semantically equivalent to the expression shown below:

XQuery Equivalent
rename $person as fn:QName("http://www.example.com/example", "manager")

Assign Assumptions

The WS-BPEL requires that "for a copy operation to be valid, the data referred to by the from-spec and the to-spec MUST be of compatible types." Hence, make sure that when you rename an element, the new name refers to a type that is compatible with the target variable. In other words, it should be of a substitutable (essentially stronger) complex type.

split-to-elements

It's impossible to split a given string into a sequence of elements using assignments. The only possible alternative is XSL which is a lot of complexity for a very simple usage pattern. The ode:splitToElements function splits a given string (that can be a variable reference) into several elements by using a specific separators. Here is an example:

<assign>
  <from>ode:split-to-elements($authorizeMessage.credential/userList, ',', 'user')</from>
  <to>$authorizedUsers</to>
</assign>

If the source element contains a list like "joe, paul, fred" the target variable will be assigned the sequence of elements:

<user>joe</user>
<user>paul</user>
<user>fred</user>

Alternatively this function can take a fourth parameter that would be the namespace of the elements used to wrap the split strings:

ode:split-to-elements(stringToSplit, separator, targetElement, targetNamespace)

Deprecated Name

This function was formerly known as splitToElements, which may still be used, but is deprecated.

combine-url(base, relative)

Takes the relative URL and combines it with the base URL to return a new absolute URL. If the relative parameter is an absolute URL, returns it instead. This function is similar to func-resolve-uri. However the latter is available in XPath 2.0 only.

compose-url(template, [name, value]*)

compose-url(template, pairs)

Expands the template URL by substituting place holders in the template, for example, ('/order/{id}', 'id', 5) returns '/order/5'. Substitute values are either name/value pairs passed as separate parameters, or a node-set returning elements with name mapping to value. The functions applies proper encoding to the mapped values. Undefined variables are replaced with an empty string. This function returns an URL. See also the URI Template spec.

expand-template(template, [name, value]*)

expand-template(template, pairs)

Similar to composeURL but undefined variables are not replaced with an empty string. They are ignored. As a result with incomplete mapping may return a new URL template.

dom-to-string

This is a function that serializes a DOM node (specified by the $node argument in the signature below) into a string.

Dom To String
ode:dom-to-string($node as node()) as xs:string

process-property

This is a function that allows you to retrieve the value of a property, defined in deploy.xml for the current process, with the given name (specified by the $name argument in the signature below, which is either a QName, String, Element or Single-Valued List).

Process Property
ode:process-property($name as item()) as node()

Basically, this method gives you a way to reference properties, defined in deploy.xml for a given process, directly in the BPEL code for that process. The $name argument refers to any schema item that resolves to a QName. The return value is the child node of the property element with the given name.

The example below illustrates how it may be used in the context of an assign activity:

<assign>
  <copy>
    <from>ode:process-property("auctionEpr")</from>
    <to partnerLink="partnerLink"/>
  </copy>
</assign>

where, the property called "epr" is defined in the corresponding deploy.xml as follows:

<deploy xmlns="http://www.apache.org/ode/schemas/dd/2007/03"
                   xmlns:tns="http://ode/bpel/process">
   <process name="tns:negotiate">
       <property name="auctionEpr">
           <sref:service-ref
                xmlns:sref=" http://docs.oasis-open.org/wsbpel/2.0/serviceref"
                xmlns:addr="http://example.com/addressing"
                xmlns:as="http://example.com/auction/wsdl/auctionService/">
                <addr:EndpointReference>
                    <addr:Address>http://example.com/auction/RegistrationService&lt;/addr:Address>
                    <addr:ServiceName>as:RegistrationService</addr:ServiceName>
                </addr:EndpointReference>
            </sref:service-ref>
        </property>...
    </process>
</deploy>

Release Information

This function will be available in the 1.3 or higher version of ODE.

Predefined Process Properties

Localhost info (name and IP address)
<bpws:assign>
  <bpws:copy>
    <bpws:from>ode:process-property('ode.localhost.name')</bpws:from>
    <bpws:to>$output.payload</bpws:to>
  </bpws:copy>
</bpws:assign>

<bpws:assign>
  <bpws:copy>
    <bpws:from>ode:process-property('ode.localhost.address')</bpws:from>
    <bpws:to>$output.payload</bpws:to>
  </bpws:copy>
</bpws:assign>

Extension Variables

Instance Id

$ode:pid

Process QName

$ode:processQName

CurrentEventDateTime

This is equivalent to current-dateTime() XPath function, which works with instance replayer.

$ode:currentEventDateTime

Release Information

1.3.4 or higher