XForms/Server-Side Field Validation

Motivation Steps Step 1: Add instances for outgoing and incoming data <!-- store the outgoing data for the invalid e-mail check --> <xf:instance id="email-out"> <data xmlns=""> <email></email> </data> </xf:instance> <!-- place to store the results of an invalid e-mail check --> <xf:instance id="email-check-results"> <data xmlns=""/> </xf:instance> Step 2: Add a submission element to the model The submission element connects the "field changed" event to a service on the server. <xf:submission id="email-check" method="get" action="email-check.xq" ref="instance('email-check')" replace="instance" instance="email-check-results" /> Step 3: Add an action to your input <xf:input ref="email" > <xf:label>Email: </xf:label> <xf:hint>This field must contain a valid email format.</xf:hint> <xf:action ev:event="xforms-value-changed"> <!-- copy from your "save-data" into the outgoing instance --> <xf:setvalue ref="instance('email-out')/email" value="instance('save-data')/email"/> <xf:send submission="email-check"/> </xf:action> </xf:input> Step 4: Add a group that displays errors if the results are invalid <xf:group ref="instance('email-check-results')/message[@class='error']"> <div class="field-warn"><xf:output value="instance('email-check-results')/message"/></div> </xf:group> Step 5: Create a server-side REST GET service that returns true/false If there are no errors just return <ok/> If there are errors return <message type="error">Invalid e-mail format</message>