APACHE SLING & FRIENDS TECH MEETUP
BERLIN, 25-27 SEPTEMBER 2017
Fun Times with Sling Models Exporters
Justin Edelson, Adobe Systems
Sling Models – Reducing Boilerplate Since ‘14
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§ OG
§ AdapterFactories
Roadmap from 2014
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§ More Standard Injectors
§ SelfInjector, SlingObjectInjector
§ AEM-specific injectors in ACS AEM Commons
§ AemObjectsInjector
§ Pluggable @Via Support
§ Done this year
✔
✔
✔
Der Mensch denkt und Gott lenkt
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§ Injector-Specific Annotations
§ ModelFactory
§ Sling Validation Integration
§ Alternate Adapter Classes
§ BND Plugin
§ Exporter Framework
Sling Models – Reducing Boilerplate Since ‘14
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§ OG
§ AdapterFactories
§ Exporter Framework
§ Format Conversion
§ Content Access Servlets
Use Cases
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§ Customized content output for external
applications
§ Isomorphic rendering – use the same model
on the client and server
In a Nutshell
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§ GET /content/something.model.json
1. Adapt the Resource to some model object
2. Transform that model to a String
3. Serve the String to the client
No Code Required*
How To
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1. Add resourceType attribute to @Model
2. Add @Exporter(name = “jackson”, extension
= “json”)
3. (Optional) Annotate model
methods/properties.
How It Works
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HTL Script
JSONHTML
Resource
Sling Model
Exporter
HTTP
Client
Jackson Exporter
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2
4
5
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HTTP GET Request is made for a resource in AEM
with the selector and extension registered with the
Sling Model’s Exporter.
Example: HTTP GET /content/my-resource.model.json
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Sling resolves the the requested resource’s
sling:resourceType, selector and extension to a
dynamically generated Sling Exporter Servlet, which is
mapped to the Sling Model with Exporter.
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e exporter serializes the Sling Model based
on the Exporter Options and Exporter-specic
Sling Model annotations and returns the
result to the Sling Exporter Servlet as a String.
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e Sling Exporter Servlet returns the String
export of the Sling Model as the HTTP
Response.
Sling Exporter Servlet
Custom Exporters
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3
e resolved Sling Exporter Servlet invokes the
Sling Model Exporter against the Sling Model
object adapted from the request or resource (as
determined by the Sling Models adaptables)
Handling Object Graphs
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§ Q: Which class needs
@Exporter?
§ A: Only ParentComponent
§ @Exporter goes on the
HTTP entrypoint
title: String
child : ChildComponent
ParentComponent
property : String
ChildComponent
title: String
child : ChildComponent
@Model
@Exporter
ParentComponent
property : String
@Model
ChildComponent
Other Conversions – Not just for Strings!
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§ ModelAdapterFactory.exportModel()
§ Examples:
§ Jackson – export to Map
§ JAXB – export to DOM Document
Multiple Exporters – Use @Exporters
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@Model(adaptables=Resource.class,
resourceType="myco/something")
@Exporters({
@Exporter(name = "jackson",
extensions = "json"),
@Exporter(name = "gson", selector = "gson",
extensions = "json")
})
Exporter Options
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§ Simple map of name/value pairs.
§ Semantics are up to ModelExporter impl.
§ Specified with
§ exportModel() API
§ @ExporterOption annotation
§ Selectors
§ Request parameters
Exporter Options - Jackson
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§ “tidy”
§ SerializationFeature.*
§ http://bit.ly/jack-serial
§ MapperFeature.*
§ http://bit.ly/jack-mapper
ExporterOption Examples
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@ExporterOption(
name =
"SerializationFeature.WRITE_DATES_AS_TIMESTAMPS",
value = ”false")
GET /content/something.model.tidy.json
GET /content/something.model.json?tidy=true
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Extension Points
Extension Point - ModelExporter
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§ Defines a new
named exporter
getName() : String
isSupported(class) : boolean
export(model, class, options) : T
<<interface>>
ModelEx porter
ModelExporter Example - GSON
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public <T> T export(Object model, Class<T> clazz,
Map<String, String> options)
throws ExportException {
return (T) new Gson().toJson(model);
}
ModelExporter Example - JAXB
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public <T> T export(Object model, Class<T> clazz,
Map<String, String> options) throws ExportException {
try {
JAXBContext jaxbContext =
JAXBContext.newInstance(model.getClass());
Marshaller marshaller = jaxbContext.createMarshaller();
StringWriter sw = new StringWriter();
marshaller.marshal(model, sw);
return (T) sw.toString();
} catch (JAXBException e) { throw new ExportException(e); }
}
Extension Point – Jackson ModuleProvider
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§ Customize serialization of classes outside
your codebase.
§ See http://bit.ly/jack-modules
§ Provided Examples:
§ Sling Resources
§ (Http|SlingHttp)?ServletRequest
§ java.util.Enumeration
Jackson ModuleProvider – Joda
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import org.joda.time.DateTime;
public class TestModel {
public DateTime getTimestamp() {
return new DateTime();
}
}
Jackson ModuleProvider – Joda (no Module)
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"timestamp" : {
"era" : 1, "dayOfYear" : 242, "dayOfWeek" : 3,
"dayOfMonth" : 30, "year" : 2017, "weekOfWeekyear" : 35,
"hourOfDay" : 12, "minuteOfHour" : 33, "monthOfYear" : 8,
"millisOfDay" : 45184141, "secondOfMinute" : 4, "millisOfSecond" : 141,
"weekyear" : 2017, "yearOfEra" : 2017, "yearOfCentury" : 17,
"centuryOfEra" : 20, "secondOfDay" : 45184, "minuteOfDay" : 753,
"zone" : {
"fixed" : false,
"uncachedZone" : {
"cachable" : true, "fixed" : false, "id" : "America/New_York”
},
"id" : "America/New_York”
},
"millis" : 1504110784141,
"chronology" : {
"zone" : {
"fixed" : false,
"uncachedZone" : {
"cachable" : true "fixed" : false, "id" : "America/New_York”
},
"id" : "America/New_York”
}
},
"afterNow" : false, "beforeNow" : true, "equalNow" : false
}
Jackson ModuleProvider - Joda
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@Component
public class JodaModuleProvider
implements ModuleProvider {
public Module getModule() {
return new JodaModule();
}
}
Jackson ModuleProvider – Joda (w/ Module)
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"timestamp" : 1504111214012
Summary
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§ Model Objects -> JSON Servlets
§ Just add annotations
§ Supported by Jackson
§ Use ModuleProvider SPI for unowned classes
§ Other formats through ModelExporter SPI
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Q&A
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Thanks!
