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; | |
| } | |
| } |
- 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; | |
| } | |
| } |
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; | |
| } | |
| } |
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) |
- If Sling Objects (eg. currentStyle, currentPage, xssApi etc) are also required, prefer adapting to SlingHttpServletRequest.
| @Model(adaptables = SlingHttpServletRequest.class, defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL) |
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; |
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; |
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; | |
| } |
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; | |
| } |
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; | |
| } |
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); | |
| } | |
| } | |
| } |
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; | |
| } |
