Sling Model annotations

Creating a Sling Model

Annotation used:

  • @Model: declares a bean as Sling Model.
  • @Inject: Injects resource property into a class variable.
  • @PostConstruct: declares the function which would initialize the bean after deriving information based on business logic. The function is called after the all injections have completed.

Example:

  • In the above example, ‘adaptables = Resource.class’ maps the sling model against a Sling Resource.
  • The @Inject would inject ‘contacts’ property from the resource into ‘contacts’ class variable. The property value injection occurs after adapting the Resource into Value Map.

Optional/Required fields

@Model annotation provides ‘defaultInjectionStrategy’ attribute to indicate if the injected fields in a sling model should be required/optional.

Injection strategy on class level:
  • Use ‘defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL’ to mark all injected fields as optional
  • Use ‘defaultInjectionStrategy = DefaultInjectionStrategy.REQUIRED’ to mark all injected fields as required. Its also the default configuration, if ‘defaultInjectionStrategy’ is not specified.
Injection strategy on Field level:
  • @Required / @Optional annotations can be used to selectively mark fields as required/optional.

Example:

Adapt Model from Resource / SlingHttpServletRequest

A Models can be adapted both Resource / SlingHttpServletRequest. This depends upon the fields required to be injected.

  • If only resource properties are required, prefer using:

  •  If Sling Objects (eg. currentStyle, currentPage, xssApi etc) are also required, prefer adapting to SlingHttpServletRequest.

Default Value

@Default allows to specify default value for fields (including arrays).
Example:

    Refer to link, to use attribute names matching with the field’s type.

Alternate field name

Use @Named if the field name is different from the property name.

Via

To inject field based on JavaBean property of the adaptable. Use with ‘SlingHttpServletRequest’ to inject property value from the resource.

Self

Inject adaptable object to a field.

Additional Notes

Design Object

The Design object can be accessed on adapting model to Resource / SlingHttpServletRequest

Injecting currentStyle object

Used when the Sling Model is adapted from SlingHttpServletRequest. Example:

Fetch currentStyle object from Resource

Used when the Sling Model is adapted from Resource. Example:

Inject OSGi Services

OSGi services can be injected via @Inject. The annotation could be used while adapting to both Resource and SlingHttpServletRequest

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