JSON support

[SINCE Orbeon Forms 2016.1]

Receiving JSON

Introduction

When an xf:submission or by an xf:instance with a src or resource attribute receives content with the application/json mediatype, Orbeon Forms parses the received JSON and converts it to an XML representation friendly to XPath expressions.

[SINCE Orbeon Forms 2017.1] In addition to the application/json mediatype, mediatypes of the form a/b+json are recognized.

Conversion examples

The following JSON object:

{ "given": "Mark", "family": "Smith" }

converts to:

<json type="object">
    <given>Mark</given>
    <family>Smith</family>
</json>

and the values can be accessed in XPath with the paths instance()/given and instance()/family.

Numbers have a type="number" attribute:

{ "name": "Mark", "age": 21 }

converts to:

<json type="object">
    <name>Mark</name>
    <age type="number">21</age>
</json>

Booleans similarly have a type="boolean" attribute:"

{ "selected": true }

converts to:

<json type="object">
    <selected type="boolean">true</selected>
</json>

Arrays use the _ element name and the type="array" attribute:

{ "cities": ["Amsterdam", "Paris", "London"] }

converts to:

<json type="object">
    <cities type="array">
        <_>Amsterdam</_>
        <_>Paris</_>
        <_>London</_>
    </cities>
</json>

and the string "Paris" can be accessed with instance()/cities/_[2].

JSON null adds a type="null" attribute:"

{ "p": null }

converts to:

<json type="object">
    <p type="null"/>
</json>

Here is a link to more examples as part of the test suite.

Seeing the converted XML

You can visualize the XML converted from JSON with Form Builder as follows:

1. Create a new form.

2. In the Advanced tab, create a new HTTP service, name it my-service, provide the URL to your JSON, and save.

3. In the Advanced tab, create a new Action, name it show-result, run it on form load after the controls are ready, have it call my-service.

4. Still while editing the new action, in the Service Response Actions tab set the value of "(control-1)" to saxon:serialize(., 'xml').

5. Hit the Text button, and you'll find the XML in the text field. To make it easier to read, copy the XML in the text field, and paste it in an XML formatting tool.

How to see the converted XML

[SINCE Orbeon Forms 2019.1]

The Form Builder HTTP Service dialog supports viewing JSON response translated into XML.

See XML view of JSON responses.

Sending JSON

When setting serialization="application/json" on xf:submission, the source XML is converted to JSON. The source XML must be compatible with the XForms XML representation of JSON shown above to be meaningful.