Mobile Forms Architecture
Ultimo aggiornamento il May 03, 2021 06:06:30 AM GMT | Valido anche per Adobe LiveCycle
Mobile Forms is deployed as a package within the embedded CQ instance and exposes Mobile Forms functionality as REST end point over HTTP/S using RESTful Apache Sling Architecture.
Using Sling Framework
Apache Sling is resource-centric. It uses a request URL to first resolve the resource. Each resource has a sling:resourceType (or sling:resourceSuperType) property. Based on this property, the request method, and properties of the request URL, a sling script is then selected to handle the request. This sling script can be a JSP or a servlet. For Mobile Forms, Profile nodes act as sling resources and Profile Renderer acts as the sling script that handles the request to render the mobile form with a particular profile. A Profile Renderer is a JSP that reads parameters from a request and calls the Forms OSGi Service.
For details on REST endpoint and supported request parameters, see Rendering Form Template.
When a user makes a request from a client device such as an iOS or Android browser, Sling first resolves the Profile Node based on the request URL. From this Profile Node, it reads sling:resourceSuperType and sling:resourceType to determine all available scripts that can handle this Form Render request. It then uses Sling request selectors along with request method to identify the script best suited for handling this request. Once the request reaches a Profile Renderer JSP, the JSP calls the Forms OSGi service.
Typical form processing call flow
Mobile Forms cache all the intermediate objects required to process (rendition or submission) a form on the first request. It does not cache the objects dependent on the data as such objects are likely to change.
Mobile Form maintains two different levels of cache, PreRender cache and Render Cache. The preRender cache contains all the fragments and images of a resolved template and Render cache contains rendered content such as HTML.
Mobile Forms do not cache templates that have missing references of fragments and images. If Mobile Forms take more than normal amount of time, then check the server logs for missing references and warnings. Also ensure that the maximum size of the object is not reached.
Forms OSGi service processes a request in two steps:
- Layout and Initial Form State generation: Forms OSGi render service calls the Forms Cache component to determine if the form has already been cached and has not been invalidated. If the form is cached and valid, it serves the generated HTML from the cache. If the form is invalidated, the Forms OSGi render service calls the LiveCycle Forms service container, which generates the Initial Form Layout and Form State in XML format. This XML is transformed into HTML layout and Initial JSON Form State by the Forms OSGi service and then cached for subsequent requests.
- Prepopulated Forms: While rendering, If a user requests forms with prepopulated data, the Forms OSGi render service calls the Forms service container and generates a new Form state with merged data. However, since the layout is already generated in the above step, this call is faster than the first call. This call only performs the data merge and runs the scripts on the data.
When a user submits the form, the browser sends state of form in JSON format to the submit service proxy; then the submit service proxy generates a data XML using JSON data and submits that data XML to submit endpoint.
Mobile Forms is delivered as a CQ package that can be managed from the CQ Package Manager available at http://:/lc/crx/packmgr/index.jsp.
adobe-lc-forms-pkg.zip: This package is the main single install package. This package contains the following subpackages and bundles:
- adobe-lc-forms-core-<version>.jar: It is an OSGi bundle that contains the OSGi components and services for the Mobile Forms.
- scala-lang-2.9.1.jar: The adobe-lc-forms-core bundle uses some scala-related libraries present in scala-lang-2.9.1.jar.
- adobe-lc-forms-content-pkg-<version>.zip: This package contains Profiles and Profile Renderer scripts and some other resources.
- adobe-lc-forms-lcconnector-<version>.jar: This OSGi Bundle contains all LiveCycle specific service implementations.
OSGi Components (adobe-lc-forms-core.jar)
Adobe XFA Forms Renderer (com.adobe.livecycle.adobe-lc-forms-core) is the display name of the Mobile Forms OSGi bundle when viewed from Bundle View of Felix admin console (http://<host>:<port>/lc/system/console/bundles).
This component contains OSGi components for render, cache management, and configuration settings.
Forms OSGi Service
This OSGi Service contains the logic to render an XDP as HTML and handles the submission of a form to generate data XML. This service uses LiveCycle Forms service container. The Forms service container internally calls native component XMLFormService.exe that performs the processing.
If a render request is received, this component calls Forms service container to generate layout and state information that is further processed to generate HTML and JSON form DOM states.
This component is also responsible for generating data XML from submitted form state JSON.
The caching mechanism described in this article is updated for LiveCycle ES4 Service Pack 1. If you are on the LiveCycle ES4 base release, follow the steps described in Key Distinctions between LiveCycle ES4 and Service pack 1.
Mobile Forms uses caching to optimize throughput and response time. You can configure the level of the cache service to fine-tune the trade-off between performance and space utilization.
Do not cache artifacts
Cache only intermediate artifacts that are generated before the render of the form like template containing inline fragments and images
Cache Rendered HTML content
Mobile Forms perform in-memory caching using LRU strategy. If cache strategy is set to None, cache is not created. LRU eviction policy is based on number of forms. You can also specify the threshold size beyond which objects are not cached.
In-memory cache is not shared between cluster nodes.
Configuration Service enables tuning the configuration parameters and cache settings for Mobile Forms.
To update these settings, go to the CQ Felix Admin Console (available at http://<server>:<port>/lc/system/console/configMgr), search for and select LC Forms Configuration.
You can configure the cache size or disable the cache using configuration service. For detailed information, see Cache Component. You can also enable debugging using Debug Options parameter. More information about debugging forms can be found at Debugging Mobile Forms.
Runtime Components (adobe-lc-forms-runtime-pkg.zip)
The Runtime Package contains the client-side libraries used to render HTML forms.
Important components available as part of Runtime package:
This scripting engine uses some of the feature of ECMAScript5 like Object.defineProperty. The engine / library is delivered as CQ Client Lib with the category name xfaforms.profile. It also provides FormBridge API to enable external portals or apps to interact with form. Using FormBridge, an external app can programmatically hide certain elements, get or set their values, or change their attributes.
For more details, see the Form Bridge article.
Layout Engine also contains a set of widgets used to capture the value of form fields from a user. These widgets are modeled as jQuery UI Widgets that implement certain additional contract to work seamlessly with Layout engine.
For more details on widgets and the corresponding contracts, see Custom Widgets for Mobile Forms.
The style associated with the HTML elements is added either inline or based on embedded CSS block. Some common styles which are not dependent on form are part of CQ Client Lib with category name xfaforms.profile.
In addition to default styling properties, each form element also contains certain CSS classes based on element type, name, and other properties. Using these classes, one can restyle elements by specifying their own CSS.
For more details on default styling and classes, see Introduction to styles.
Server-Side script and Web Services
Any scripts that are marked to run-at-server or marked to call a Web Service (regardless of where it is marked to execute) always executes on server.
The client script engine:
- Makes a synchronous call to the server passing the current Form state in the form of JSON
- Executes the script or Web Service on the server
- Generates a new JSON state
- Merges the new JSON state on the client when the response is returned.
Localization Resource Bundles
By default, Mobile Forms is supported in English, French, German, and Japanese language. Based on the locale received in the request header, corresponding Resource Bundle is sent to the client. This resource bundle is added to Profile JSP as a CQ Client Lib with category name xfaforms.I18N. You can override the logic of picking up the locale package in the profile.
Sling Components (adobe-lc-forms-content-pkg.zip)
Sling package contains content related to Profiles and Profile Renderer.
Profiles are the Resource nodes in sling that represent a form or Family of Forms. At the CQ Level, these profiles are JCR nodes. The nodes reside under the /content folder in JCR repository and can be inside any sub folder under the /content folder.
The Profile node has a property sling:resourceSuperType with value xfaforms/profile. This property internally sends forward requests to the sling script for Profile nodes located in the /libs/xfaforms/profile folder. These scripts are JSP pages, that are containers for putting together the HTML forms and required JS/CSS artifacts. The pages include references to:
- xfaforms.I18N.<locale>: This library contains localized data.
- xfaforms.profile: This library contains implementation for XFA Scripting and Layout engine.