Sling models by Justin Edelson

Sling Models
Justin Edelson – Technical Architect, Adobe

Let’s say you want to adapt a Resource into some domain object…

public class OldModel {
private String title;
private String description;
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
}

@Component
@Service
@Properties({
@Property(name=AdapterFactory.ADAPTABLE_CLASSES, value="org.apache.sling.api.Resource"),
@Property(name=AdapterFactory.ADAPTER_CLASSES,
value="com.adobe.people.jedelson.slingmodels.demo.OldModel")
})
public class OldModelAdapterFactory implements AdapterFactory {
@SuppressWarnings("unchecked")
public <AdapterType> AdapterType getAdapter(Object adaptable, Class<AdapterType> type) {
if (adaptable instanceof Resource && type.equals(OldModel.class)) {
OldModel model = new OldModel();
ValueMap map = ResourceUtil.getValueMap((Resource) adaptable);
model.setTitle(map.get(”title", String.class));
model.setDescription(map.get(”description", String.class));
return (AdapterType) model;
} else {
return null;
}
}
}

OldModel myModel = resource.adaptTo(OldModel.class)
<sling:adaptTo adaptable="${resource}" adaptTo=”…
OldModel" var=”myModel" />
<div data-sly-use.myModel =“…OldModel”></div>

@Model(adaptables = Resource.class)
public class NewModel {
@Inject
private String title;
@Inject
private String description;
public String getTitle() {
return title;
}
public String getDescription() {
return description;
}
}

NewModel myModel = resource.adaptTo(NewModel.class)
<sling:adaptTo adaptable="${resource}" adaptTo=”…
NewModel" var=”myModel" />
<div data-sly-use.myModel=“…NewModel”></div>

• The “old” way: 30+ LOC
• The “new” way: 13 LOC
– Plus one extra bundle header:
<Sling-Model-Packages>com.adobe.people.jedelson.slingmodels.demo</Sling-Model-Packages>

public interface NewModel2 {
@Inject
public String getTitle();
@Inject
public String getDescription();
}

• 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 these objects are different than any other adapter factory
• Support both classes and interfaces.
• Work with existing Sling infrastructure (i.e. not require changes to other bundles).

• December 2013 – YAMF prototype
announced on sling-dev
• January 2014 – API formalized and renamed
to Sling Models
• Feburary 2014 – 1.0.0 release; Included in
AEM 6.0 Beta
• March 2014 – 1.0.2 release; Included in AEM
6.0 Release

• Standard Injectors
– SlingBindings objects
– ValueMap properties
– Child Resources
– Request Attributes
– OSGi Services

• @org.apache.sling.models.annotations.Model
• @javax.inject.Inject
• @javax.inject.Named
• @org.apache.sling.models.annotations.Optional
• @org.apache.sling.models.annotations.Source
• @org.apache.sling.models.annotations.Filter
• @javax.inject.PostConstruct
• @org.apache.sling.models.annotations.Via
• @org.apache.sling.models.annotations.Default

• @Model(adaptables = Resource.class)
• @Model(adaptables = SlingHttpServletRequest.class)
• @Model(adaptables = { Resource.class, ValueMap.class })

• @Inject private String title;
– valueMap.get(“title”, String.class);
• @Inject public String getTitle();
– valueMap.get(“title”, String.class);
• @Inject private String[] columnNames;
– valueMap.get(“columnNames”, String[].class);
• @Inject private List<Filter> filters;
– bundleContext.getServiceReferences(“javax.servlet.Filter”)

• By default, the name of the field or method is
used to perform the injection.
• @Inject @Named(“jcr:title”) private String
title;
– valueMap.get(“jcr:title”, String.class);

• By default, all @Inject points are required.
• resource.adaptTo(Model.class) <- returns null
• @Inject @Optional private String title;

• request.getAttribute(“text”) <- returns “goodbye”
• slingBindings.get(“text”) <- returns “hello”
• @Inject
private String text; <- “hello” (SlingBindings is checked first)
• @Inject @Source(“request-attributes”)
private String text; <- “goodbye”

• Specifically for OSGi services:
• @Inject @Filter("(sling.servlet.extensions=json)") private
List<Servlet> servlets;
• Implicitly applies @Source(“osgi-services”)

• @Inject private String text;
• @PostConstruct
protected void doSomething() { log.info("text = {}", text); };
• Superclass @PostConstruct methods called first.

@Model(adaptables = SlingHttpServletRequest.class)
public class ViaModel {
@Inject @Via("resource")
private String firstProperty;
public String getFirstProperty() {
return firstProperty;
}
}

• @Inject @Default(values=“default text”)
private String text;
• Also
– booleanValues
– doubleValues
– floatValues
– intValues
– longValues
– shortValues

If you need the adaptable itself:
@Model(adaptables = SlingHttpServletRequest.class)
public class ConstructorModel {
private final SlingHttpServletRequest request;
public ConstructorModel(SlingHttpServletRequest r) {
this.request = r;
}
public SlingHttpServletRequest getRequest() {
return request;
}
}

public interface ChildValueMapModel {
@Inject
public ValueMap getFirstChild();
}
resource.getChild(“firstChild”).adaptTo(ValueMap.class)

public interface ParentModel {
@Inject
public ChildModel getFirstChild();
}
Works even if resource.adaptTo(ChildModel.class) isn’t done
by Sling Models

• Injectors are OSGi services implementing the
org.apache.sling.models.spi.Injector interface
• Object getValue(Object adaptable, String name, Type
type, AnnotatedElement element, DisposalCallbackRegistry
callbackRegistry)
• adaptable – the object being adapted
• name – the name (either using @Named or the default
name)
• element – the method or field
• callbackRegistry – Injector gets notified when the adapted
model is garbage collected

public Object getValue(Object adaptable, String name,
Type type, AnnotatedElement element, DisposalCallbackRegistry callbackRegistry) {
Resource resource = getResource(adaptable);
if (resource == null) {
return null;
} else if (type instanceof Class<?>) {
InheritanceValueMap map = new
HierarchyNodeInheritanceValueMap(resource);
return map.getInherited(name, (Class<?>) type);
} else {
return null;
}
}

• Some injectors need extra data
– Example: OSGi service filters
@Target({ ElementType.FIELD, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Qualifier
@Source("resource-path")
public @interface ResourcePath {
String value();
}

public Object getValue(Object adaptable, String name,
Type declaredType, AnnotatedElement element,
DisposalCallbackRegistry callbackRegistry) {
ResourcePath path =
element.getAnnotation(ResourcePath.class);
if (path == null) {
return null;
}
ResourceResolver resolver = getResourceResolver(adaptable);
if (resolver == null) {
return null;
}
return resolver.getResource(path.value());
}

public interface ResourcePathModel {
@Inject @ResourcePath("/content/dam")
Resource getResource();
}

• More Standard Injectors
• AEM-specific injectors in ACS AEM Commons
• Pluggable @Via support

Sling models by Justin Edelson

More Related Content

What's hot (20)

Similar to Sling models by Justin Edelson (20)

More from AEM HUB (20)

Recently uploaded (20)

Sling models by Justin Edelson