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:

	@Model(adaptables = Resource.class)

	public class ContactUsModel {

	private String mailAddress;

	private String phoneNumber;

	@Inject
	protected String title;

	@Inject
	protected String officeCode;

	@PostConstruct
	protected void init() {
	// Business logic to transform injected values and assign to bean variables
	// Example: Resolve mailAddress/phoneNumber applicable for the user's region, based on officeCode
	}

	public String getMailAddress(){
	return mailAddress;
	}

	public String getPhoneNumber(){
	return phoneNumber;
	}
	}

view raw

Inject

hosted with ❤ by GitHub

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.

	@Model(adaptables = Resource.class, defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)
	public class ContactUsModel {

	private String mailAddress;

	private String phoneNumber;

	@Inject
	@Required
	protected String title;

	@Inject
	protected String officeCode;

	@PostConstruct
	protected void init() {
	// Business logic to transform the Injected values and assign to bean Variables
	// Example: Resolve mailAddress/phoneNumber applicable for the user's region, based on officeCode
	}

	public String getMailAddress(){
	return mailAddress;
	}

	public String getPhoneNumber(){
	return phoneNumber;
	}
	}

view raw

Optional-Required

hosted with ❤ by GitHub

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:

	@Model(adaptables = Resource.class, defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)
	public class ContactUsModel {

	private String mailAddress;

	private String phoneNumber;

	@Inject
	@Required
	protected String title;

	@Inject
	protected String officeCode;

	@PostConstruct
	protected void init() {
	// Business logic to transform the Injected values and assign to bean Variables
	// Example: Resolve mailAddress/phoneNumber applicable for the user's region, based on officeCode
	}

	public String getMailAddress(){
	return mailAddress;
	}

	public String getPhoneNumber(){
	return phoneNumber;
	}
	}

view raw

Optional-Required

hosted with ❤ by GitHub

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:

@Model(adaptables = Resource.class, defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)

view raw

Model-Resource

hosted with ❤ by GitHub

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

@Model(adaptables = SlingHttpServletRequest.class, defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)

view raw

Model-SlingHttpServletRequest

hosted with ❤ by GitHub

Default Value

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

Example:

	@Inject @Default(values="Contact Us")
	private String title;

	@Inject @Default(intValues={1,2,3,4})
	private int[] integers;

view raw

Default

hosted with ❤ by GitHub

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.

	@Inject @Named("jcr:created")
	private String created;

view raw

Named

hosted with ❤ by GitHub

Via

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

	@Model(adaptables = SlingHttpServletRequest.class, defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)
	public class ContactUsModel {
	@Inject @Via("resource")
	private String title;
	}

view raw

Via

hosted with ❤ by GitHub

Self

Inject adaptable object to a field.

	@Model(adaptables = SlingHttpServletRequest.class, defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)
	public class ContactUsModel {
	//Accessing the resource that is adapted to ContactusModel
	@Self
	protected Resource resource;
	}

view raw

Self

hosted with ❤ by GitHub

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:

	@Model(adaptables = SlingHttpServletRequest.class, defaultInjectionStrategy = DefaultInjectionStrategyzOPTIONAL)
	public class ContactUsModel {
	@Inject
	private Style currentStyle;
	}

view raw

currentStyle

hosted with ❤ by GitHub

Fetch currentStyle object from Resource

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

	@Model(adaptables = Resource.class, defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)
	public class ContactUsModel {
	private Style currentStyle;
	private Designer designer;

	@PostConstruct
	protected void init() {

	// Getting the currentStyle from the Designer.class
	designer = this.resourceResolver.adaptTo(Designer.class);
	if (designer != null) {
	currentStyle = designer.getStyle(resource);
	}
	}
	}

view raw

currentStyle-from-Resource

hosted with ❤ by GitHub

Inject OSGi Services

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

	@Model(adaptables = SlingHttpServletRequest.class, defaultInjectionStrategy = DefaultInjectionStrategyzOPTIONAL)
	public class ContactUsModel {

	@Inject
	private ResourceResolver resourceResolver;
	}

view raw

OSGi Service

hosted with ❤ by GitHub

Creating a Sling Model

Optional/Required fields

Injection strategy on class level:

Injection strategy on Field level:

Adapt Model from Resource / SlingHttpServletRequest

Default Value

Alternate field name

Via

Self

Additional Notes

Design Object

Injecting currentStyle object

Fetch currentStyle object from Resource

Inject OSGi Services

Share this:

Like this:

Leave a Reply Cancel reply