Sling Models allow for dependency injection and adaptation of Sling objects into POJOs using annotations. This document discusses how Sling Models work, the annotations used to configure them, standard injectors, and how to use Sling Models with Sightly and JSP. It also provides a live demo and references for further information.

1. Sling Models Using Sightly
and JSP
DEEPAK KHETAWAT

2. About the Speaker

3. What & Why Sling Models
- What are Sling Models
- Design Goals
- Why Sling Models ?
Sling Model Annotations
- Annotations Usage
Sling Model Injectors
- What are Injectors
- Injectors available in 1.0.x and 1.1.x
- Injector-specific Annotations
Agenda
Usage of Sling Models
- Prerequisite
- How to use Sling Models with JSP ?
- How to use Sling Models with Sightly?
Demo
- Functionality Demo
Appendix and Q&A
- Appendix
- Q&A

4. What & Why Sling Models

5. • Sling Models are POJO’s which are automatically
mapped from Sling objects, typically resources, request
objects. Sometimes these POJOs need OSGi services
as well
What are Sling Models?

6. • Entirely annotation driven. "Pure" POJOs
• Adapt multiple objects
• Work with existing Sling infrastructure
• Client doesn't know/care that these objects are different than any
other adapter factory
• Support both classes and interfaces
• Pluggable
Design Goals

7. Development :
• Saves from creating own adapters
• Situation Based Dependency Injection Framework
• Do More with less code making code readable and Removing
redundant (boilerplate) code
Testing :
• Highly Testable Code
- Sling Model Inject Annotations defines binding to
dependencies
- Mock dependencies with tools like Mockito using
@InjectMocks
Why Sling Models ?

8. Sling Model Annotations

9. Annotations Usage
Sling Model Annotation Code Snippet Description
@Model @Model(adaptables = Resource.class) Class is annotated with @Model and the adaptable class
@Inject
@Inject private String propertyName; (class )
@Inject String getPropertyName(); (interface )
A property named "propertyName" will be looked up from the
Resource (after first adapting it to a ValueMap) and it is injected ,
else will return null if property not found .
@Default @Inject @Default(values = "AEM") private String technology; A default value (for Strings , Arrays , primitives etc. )
@Optional @Inject @Optional private String otherName.
@Injected fields/methods are assumed to be required. To mark
them as optional, use @Optional i.e resource or adaptable may or
may not have property .

10. Annotations Usage
Sling Model Annotation Code Snippet Description
@Named @Inject @Named("title") private String pageTitle;
Inject a property whose name does NOT match the Model field
name
@Via
@Model(adaptables=SlingHttpServletRequest.class)
public interface SlingModelDemo {
@Inject @Via("resource") String getPropertyName(); }
Use a JavaBean property of the adaptable as the source of the
injection
// Code Snippet will return
request.getResource().adaptTo(ValueMap.class).get("propertyNam
e", String.class)
@Source
@Model(adaptables=SlingHttpServletRequest.class)
@Inject @Source("script-bindings") Resource
getResource(); }
Explicitly tie an injected field or method to a particular injector (by
name). Can also be on other annotations
//Code snippet will ensure that "resource" is retrieved from the
bindings, not a request attribute
@PostConstruct
@PostConstruct
protected void sayHello() { logger.info("hello"); }
Methods to call upon model option creation (only for model classes)

11. Sling Model Injectors

12. • Injectors are OSGi services implementing the
org.apache.sling.models.spi.Injector interface
• Injectors are invoked in order of their service ranking, from lowest to
highest.
What are Injectors ?

13. • Script Bindings (script-bindings)
• Value Map (valuemap)
• Child Resources (child-resources)
• Request Attributes (request-attributes)
• OSGI Service References (osgi-services)
Standard Injectors in 1.0.x
Injectors (with @Source names)

14. Injects adaptable itself or an object that can be adapted from
adaptable
@Self privateResource resource;
@Model(adaptables = SlingHttpServletRequest.class)
public class SlingModelDemo {
@SlingObject private Resource resource;
@SlingObject private SlingHttpServletRequest request;
}
Injects resource from given path , applicable to Resource or
SlingHttpServletRequest objects
@ResourcePath(path="/resource-path") private Resource resource;
• Self Injector (self)
• Sling Object Injector (sling-object)
• Resource Path Injector (resource-path)
Standard Injectors in 1.1.x
Injectors (with @Source names)

15. • Supported since Sling Models Impl 1.0.6
• Can use customized annotations with following advantages over
using the standard annotations:
- Less code to write (only one annotation is necessary in most of
the cases)
- More robust
• Injector Specific Annotation specifies source explicitly
• Example
@ValueMapValue String propertyName;
@ValueMapValue (name="jcr:title", optional=true)
String title;
Injector-specific Annotations
Annotation
Supported Optional
Elements
Injector
@ScriptVariable optional and name script-bindings
@ValueMapValue optional, name and via valuemap
@ChildResource optional, name and via child-resources
@RequestAttribute optional, name and via request-attributes
@ResourcePath
optional, path,
and name
resource-path
@OSGiService optional, filter osgi-services
@Self optional self
@SlingObject optional sling-object

16. Injectors depicted in Felix Console

17. Using Sling Models with Sightly and JSP

18. • Need org.apache.sling.models.api package
- OOTB supported in AEM 6 and above version , with
org.apache.sling.models.api package already present in AEM
instance
- For other versions download package from
http://sling.apache.org/downloads.cgi and install in AEM instance
• Maven dependency can be found at
http://<host>:<port>/system/console/depfinder , search for
org.apache.sling.models.annotations.Model
<dependency> <groupId>org.apache.sling</groupId>
<artifactId>org.apache.sling.models.api</artifactId>
<version>1.0.0</version> <scope>provided</scope>
</dependency>
Prerequisite

19. • Search for maven-bundle-plugin in pom.xml file , update it with
following
- <Sling-Model-Packages> com.slingmodels.core </Sling-Model-
Packages>
- It is because for Sling Model classes to be picked up this header
must be added to the bundle's manifest
Prerequisite

20. • Supported as of Sling Models 1.1.0
• Name of a constructor argument parameter cannot be detected
via the Java Reflection API
• @Named annotation is mandatory for injectors that require a
name for resolving the injection
• @Model(adaptables=Resource.class)
public class MyModel {
@Inject public MyModel(@Named("propertyName") String
propertyName)
{ // constructor code }
}
Constructor Injections

21. • Sling Model class object can be used in JSP by either
- <c:set var = "slingModel" value="<%=
resource.adaptTo(SlingModelDemo.class)%>" />
Or
- <sling:adaptTo adaptable="${resource}"
adaptTo="com.slingmodels.core.SlingModelDemo"
var=“slingModel"/>
Sling Models with JSP

22. • Sightly is a beautiful mark up language providing advantages like
separation of concerns , prevents xss vulnerabilities .
• Sling Model class object can be used in Sightly by :
<div data-sly-use.slingModel ="
com.slingmodels.core.SlingModelDemo">
Sling Models with Sightly

23. Demo

24. • Retrieving dialog values of a component
• Retrieving recent pages/articles under a content path
• Many more 
Groovifying Demo UseCases :

25. Code can be found at:
https://github.com/deepakkhetawat/Sling-Model-Demo.git
Where is the Code ?

26. Appendix and Q&A

27. • https://sling.apache.org/documentation/bundles/models.html
• http://slideshare.net/justinedelson/sling-models-overview
• https://sling.apache.org/documentation/bundles/sling-scripting-jsp-
taglib.html
Appendix

28. Q&A

29. For more information contact:
DEEPAK KHETAWAT
M +91-9910941818
deepak.khetawat@tothenew.com
Thank you