On this page we describe what item providers are, list their main advantages and show a few examples of using them.
Overview
Item providers are a means for accessing items from data sources. Developed for the Magnolia 6 UI, item providers are intended to cover one or more of the following two generic use cases:
- Item provider definition in a sub app descriptor, usually in the detail sub app.
- Item provider definition In a form containing composite and complex fields. In this use, the provider replaces the former field transformer functionality that is part of the UI framework 5, but no longer part of the Magnolia 6 UI.
Advantages of using item providers
Item Provider Strategy is a much simpler solution than the 5 UI field transformers. An item provider only needs to know how to access the data. In contrast, the transformers in the 5 UI framework were responsible for both types of data operations – reading and writing. In addition:
- The number of item providers is much lower in Magnolia 6 UI, compared to a relatively high number of field transformers in the 5 UI.
- The provider implementations can handle also JSON structures, task and notifications items, assets or a specific product content items.
The following item provider types are currently available:
jcrNodeFromLocationProvider
- Resolves node content from the current location.jcrGetCurrentNode
- Returns the parent node.jcrGetChildNode
- Resolves child JCR node from the parent.jsonProvider
- Usable mainly in REST -related contexts, for example in client definitions of the REST Client module, it replaces the{id}
path parameter with the one passed in the location and then fetches the result using a configured REST call.
The jcrGetCurrentNode
and jcrGetChildNode
providers are suitable for sub forms only since a dependency on a parent node is presupposed to exist.
Used in a sub app definition
In a sub app definition, a strategy is implemented for example in the Pages app, where the jcrNodeFromLocationProvider
is used (see line 7 below). This provider type resolves a JCR node from location context:
detail: class: info.magnolia.pages.app.detail.PageDetailDescriptor datasource: $type: jcrDatasource workspace: website itemProvider: $type: jcrNodeFromLocationProvider
(A snippet of an existing full definition, see https://git.magnolia-cms.com/projects/MODULES/repos/pages/browse/magnolia-pages-app/src/main/resources/pages-app/apps/pages-app.yaml.)
An item provider is not limited only to operations related to JCR content. See the following definition, where content items are provided from a JSON structure through the use of the jsonProvider
(line 16):
view: label: View Commit class: info.magnolia.ui.contentapp.detail.DetailDescriptor datasource: $type: jsonDatasource restClient: bitbucket restCall: commit jsonPathExpressions: properties: author: '$.author.raw' actions: cancel: label: Cancel $type: closeAction itemProvider: $type: jsonProvider
(A snippet of an existing full definition, see https://git.magnolia-cms.com/projects/MODULES/repos/rest-client/browse/declarative-rest-demo/apps/commits.yaml#50-65.)
Used in a form definition
A strategy can be used to handle data-read operations in forms containing complex field. Consider the following definition of a complex field called address
, composed of two simple fields, city
and country
.
address: label: address i18n: true $type: compositeField itemProvider: $type: fetchJcrSubNodeProvider properties: city: label: city $type: textField country: label: country i18n: true $type: textField
(A snippet of an existing full definition, see https://git.magnolia-cms.com/projects/MODULES/repos/contacts-app/browse/src/main/resources/contacts/apps/contacts-v8.yaml#320-336.)
Using the fetchJcrSubNodeProvider
resolves the content of the child items city
and country
from the parent address
: