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This functionality has been renamed Sling Models and is documented at http://sling.apache.org/documentation/bundles/models.html

 

 

Many Sling projects want to be able to create model objects - POJOs which are automatically mapped from Sling objects, typically resources, but also request objects. Sometimes these POJOs need OSGi services as well.

YAMF is an attempt to consolidate the various approaches I have seen to this problem.

Design Goals

  • Entirely annotation driven. "Pure" POJOs.
  • Use standard annotations where possible.
  • Pluggable
  • OOTB, support resource properties (via ValueMap), SlingBindings, OSGi services, request attributes
  • Adapt multiple objects - minimal required Resource and SlingHttpServletRequest
  • Client doesn't know/care that YAMF is involved
  • Support both classes and interfaces.
  • Work with existing Sling infrastructure (i.e. not require changes to other bundles).

Basic Usage

In the simplest case, the class is annotated with @Model and the adaptable class. Fields which need to be injected are annotated with @Inject:

In this case, a property named 'propertyName' will be looked up from the Resource (after first adapting it to a ValueMap) and it is injected.
 
For an interface, it is similar:


In order for these classes to be picked up, there is a header which must be added to the bundle's manifest:


Client Code

Client code doesn't need to be aware that YAMF is being used. It just uses the Sling Adapter framework:

 

Or

Or

 

As with other AdapterFactories, if the adaptation can't be made for any reason, adaptTo() returns null.


Other Options

If the field or method name doesn't exactly match the property name, @Named can be used:


@Injected fields/methods are assumed to be required. To mark them as optional, use @Optional:


A default value can be provided (for Strings & primitives):

Defaults can also be arrays:

 


OSGi services can be injected:


 
In this case, the name is not used -- only the class name. Lists and arrays are supported:


 
OSGi injection can be filtered:


 
The @PostConstruct annotation can be used to add methods which are invoked upon completion of all injections:


@PostConstruct methods in a super class will be invoked first.
 
If the injection should be based on a JavaBean property of the adaptable, you can indicate this using the @Via annotation:

If there is ambiguity where a given injection could be handled by more than one injector, the @Source annotation can be used to define which injector is responsible:



If the injected object does not match the desired type and the object implements the Adaptable interface, YAMF will try to adapt it. This provides the ability to create rich object graphs. For example:

When a resource is adapted to MyModel, a child resource named image is automatically adapted to an instance of ImageModel.

Annotation Reference

  • @Model - declares a model class or interface
  • @Inject - marks a field or method as injectable
  • @Named - declare a name for the injection (otherwise, defaults based on field or method name).
  • @Optional - marks a field or method injection as optional
  • @Source - explictly tie an injected field or method to a particular injector (by name). Can also be on other annotations.
  • @Filter - an OSGi service filter
  • @PostConstruct - methods to call upon model option creation (only for model classes)
  • @Via - use a JavaBean property of the adaptable as the source of the injection
  • @Default - set default values for a field or method

Available Injectors

TitleName (for @Source)DescriptionApplicable To (including using @Via)Notes
Value MapvaluemapGets a property from a Value MapAny object which is or can be adapted to a ValueMap 
OSGI Servicesosgi-servicesLookup services based on class nameAny objectEffectively ignores name.
Script Bindingsscript-bindingsLookup objects in the script bindings objectA ServletRequest object which has the Sling Bindings attribute defined 
Child Resourceschild-resourcesGets a child resource by nameResource objects 
Request Attributesrequest-attributesGet a request attributeServletRequest objects 
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2 Comments

  1. I tried to use YAMF in my JSP as <c:set var="myModel" value="<%=resource.adaptTo('org.apache.sling.yamf.it.models.MyModel')%>"/> while TLD is not ready.

    It worked almost fine except returning null when I added org.apache.sling.api.resource.Resource or any other required non-property field.

    <c:set var="myModel" value="<%=slingRequest.adaptTo('org.apache.sling.yamf.it.models.MyModel')%>"/> is vice-versa: injects Resource but not simple String properties.

    What can you suggest? I can contribute with some coding if you gave me your solution.

  2. Hi Vasily Lazerko, these questions are better posted to the sling-dev or sling-users mailing lists.

    I'm not sure what you mean by "TLD is not ready". There's no TLD for YAMF and there shouldn't need to be one. This would violate one of the design goals ("Client doesn't know/care that YAMF is involved")

    Your description is a bit vague and references a class which doesn't exist. Can you explain in a bit more detail? Is anything logged?