Service call on value change

form.xml

<xh:html xmlns:xh="http://www.w3.org/1999/xhtml" xmlns:xf="http://www.w3.org/2002/xforms"
         xmlns:xs="http://www.w3.org/2001/XMLSchema"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns:ev="http://www.w3.org/2001/xml-events"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         xmlns:xxi="http://orbeon.org/oxf/xml/xinclude"
         xmlns:xxf="http://orbeon.org/oxf/xml/xforms"
         xmlns:exf="http://www.exforms.org/exf/1-0"
         xmlns:fr="http://orbeon.org/oxf/xml/form-runner"
         xmlns:saxon="http://saxon.sf.net/"
         xmlns:sql="http://orbeon.org/oxf/xml/sql"
         xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
         xmlns:fb="http://orbeon.org/oxf/xml/form-builder">
    <xh:head>
        <xh:title>Service call</xh:title>
        <xf:model id="fr-form-model" xxf:expose-xpath-types="true">

            <!-- Main instance -->
            <xf:instance id="fr-form-instance" xxf:exclude-result-prefixes="#all">
                <form>
                    <section-1>
                        <my-service-trigger/>
                        <my-service-result/>
                    </section-1>
                </form>
            </xf:instance>

            <!-- Bindings -->
            <xf:bind id="fr-form-binds" ref="instance('fr-form-instance')">
                <xf:bind id="section-1-bind" name="section-1" ref="section-1">
                    <xf:bind id="my-service-result-bind" ref="my-service-result" name="my-service-result"/>
                    <xf:bind id="my-service-trigger-bind" ref="my-service-trigger" name="my-service-trigger"/>
                </xf:bind>
            </xf:bind>

            <!-- Metadata -->
            <xf:instance xxf:readonly="true" id="fr-form-metadata" xxf:exclude-result-prefixes="#all">
                <metadata>
                    <application-name>a</application-name>
                    <form-name>a</form-name>
                    <title xml:lang="en">Service call</title>
                    <description xml:lang="en"/>
                    <singleton>false</singleton>
                </metadata>
            </xf:instance>

            <!-- Attachments -->
            <xf:instance id="fr-form-attachments" xxf:exclude-result-prefixes="#all">
                <attachments>
                    <css mediatype="text/css" filename="" size=""/>
                    <pdf mediatype="application/pdf" filename="" size=""/>
                </attachments>
            </xf:instance>

            <!-- All form resources -->
            <!-- Don't make readonly by default in case a service modifies the resources -->
            <xf:instance id="fr-form-resources" xxf:readonly="false" xxf:exclude-result-prefixes="#all">
                <resources>
                    <resource xml:lang="en">
                        <my-service-trigger>
                            <label>Value which on change triggers service call</label>
                            <hint/>
                            <item>
                                <label>First choice</label>
                                <value>1</value>
                            </item>
                            <item>
                                <label>Second choice</label>
                                <value>2</value>
                            </item>
                            <item>
                                <label>Third choice</label>
                                <value>3</value>
                            </item>
                        </my-service-trigger>
                        <section-1>
                            <label>Untitled Section</label>
                        </section-1>
                        <my-service-result>
                            <label>Shows result from service call</label>
                            <hint/>
                        </my-service-result>
                    </resource>
                </resources>
            </xf:instance>

            <!-- Utility instances for services -->
            <xf:instance id="fr-service-request-instance" xxf:exclude-result-prefixes="#all">
                <request/>
            </xf:instance>

            <xf:instance id="fr-service-response-instance" xxf:exclude-result-prefixes="#all">
                <response/>
            </xf:instance>

            <xf:instance id="my-service-instance" class="fr-service" xxf:exclude-result-prefixes="#all">
                <body xmlns:fbf="java:org.orbeon.oxf.fb.FormBuilder"
                      xmlns:secure="java:org.orbeon.oxf.util.SecureUtils"
                      xmlns:p="http://www.orbeon.com/oxf/pipeline"
                      xmlns:frf="java:org.orbeon.oxf.fr.FormRunner">&lt;dummy/&gt;</body>
            </xf:instance>
            <xf:submission id="my-service-submission" class="fr-service"
                           ref="instance('fr-service-request-instance')"
                           resource="http://httpbin.org/xml"
                           method="get"
                           serialization="application/xml"
                           mediatype="application/xml"
                           replace="instance"
                           instance="fr-service-response-instance"/>
            <xf:action id="my-service-call-binding">
                <!-- React to event... on control... -->
                <xf:action event="xforms-value-changed" ev:observer="my-service-trigger-control"
                           if="true()">
                    <!-- Service to call -->
                    <xf:send submission="my-service-submission"/>
                </xf:action>
                <!-- Request actions -->
                <xf:action event="xforms-submit" ev:observer="my-service-submission">
                    <!-- Get reference to initial request -->
                    <xf:var name="request-instance-name" value="'my-service-instance'" as="xs:string"/>
                    <!-- Copy over to read-write request instance -->
                    <xf:insert ref="instance('fr-service-request-instance')"
                               origin="saxon:parse(instance($request-instance-name))"/>
                    <!--<xf:insert ref="instance('fr-service-request-instance')" origin="instance($request-instance-name)"/>-->
                    <!-- Set values if needed -->
                    <xf:action context="instance('fr-service-request-instance')">
                        <!-- Setvalue actions will be here -->
                    </xf:action>
                </xf:action>
                <!-- Response actions -->
                <xf:action event="xforms-submit-done" ev:observer="my-service-submission"
                           context="instance('fr-service-response-instance')">
                    <xf:action class="fr-set-control-value-action">
                        <xf:var name="control-name" value="'my-service-result'"/>
                        <xf:var name="control-value" value="/slideshow/slide[1]/title"/>
                    </xf:action>
                    <!-- Response actions will be here -->
                </xf:action>
            </xf:action>
        </xf:model>
    </xh:head>
    <xh:body>
        <fr:view>
            <fr:body xmlns:xbl="http://www.w3.org/ns/xbl" xmlns:p="http://www.orbeon.com/oxf/pipeline"
                     xmlns:oxf="http://www.orbeon.com/oxf/processors">
                <fr:section id="section-1-control" bind="section-1-bind">
                    <xf:label ref="$form-resources/section-1/label"/>
                    <fr:grid>
                        <xh:tr>
                            <xh:td>
                                <xf:select1 id="my-service-trigger-control" bind="my-service-trigger-bind"
                                            appearance="dropdown">
                                    <xf:label ref="$form-resources/my-service-trigger/label"/>
                                    <xf:hint ref="$form-resources/my-service-trigger/hint"/>
                                    <xf:alert ref="$fr-resources/detail/labels/alert"/>
                        
                        
                                    <xf:itemset ref="$form-resources/my-service-trigger/item">
                                        <xf:label ref="label"/>
                                        <xf:value ref="value"/>
                                    </xf:itemset>
                                </xf:select1>
                                
                            </xh:td>
                            <xh:td>
                                <xf:output id="my-service-result-control" bind="my-service-result-bind">
                                    <xf:label ref="$form-resources/my-service-result/label"/>
                                    <xf:hint ref="$form-resources/my-service-result/hint"/>
                                    <xf:alert ref="$fr-resources/detail/labels/alert"/>
                        
                        
                                </xf:output>
                            </xh:td>
                        </xh:tr>
                        <xh:tr>
                            <xh:td/>
                            <xh:td/>
                        </xh:tr>
                    </fr:grid>
                </fr:section>
            </fr:body>
        </fr:view>
    </xh:body>
</xh:html>