Usage of @Via in sling models | Community
Skip to main content
Nitiks25
New Participant
October 11, 2017
Solved

Usage of @Via in sling models

  • October 11, 2017
  • 25 replies
  • 28618 views

I understand from the documentation, that @Via is used to inject objects not available through the adaptable mapped to the model

In that case, if my adaptable is Resource.class and I have to inject SlingHttpServletRequset or SlingHttpServletResponse. I will have to use @Inject @Via to fetch it from SlingHttpServletRequest adaptable?

In that case, what is the parameter I have to pass to @Via?

In case of resource, it will be @Via ("resource") - what will it be for slingRequest?

This post is no longer active and is closed to new replies. Need help? Start a new post to ask your question.
Best answer by VeenaVikraman

Nitik,

  Let me try to explain you what I understand here . Let us take the simple example from what documentation Scott has shared

  - So this says ; when the model's adaptable is SlingHttpServletRequest , then when you try to inject getPropertyName() ; it will be return the property via resource method of the SlingHttpServletRequest object "request" like the below

request.getResource().getValueMap().get("propertyName", String.class)

That said , if you check the API SlingHttpServletRequest (Apache Sling Aggregate 5-incubator API)  you can understand that a resource can be fetched from a request , but the vice versa is not possible .

    So basically that means inject the value via resource API in SlingHttpServletRequest API.

  I am not aware of a way to get a request object from a resource and hence I don't believe something like below is even possible

@Model(adaptables=Resource.class)

public class MyModel

    @Inject

    @Via("request")

    private String someObj;

}

For further reading the below section explains what all standard types are provided via while and how it is implemented

Apache Sling :: Sling Models

The other thing you can do is to adapt the SlingHttpServletRequest and get the resource from it

@Model(adaptables = SlingHttpServletRequest.class)

public class MyModel {

  

     @Inject

     SlingHttpServletRequest request;

     @PostConstruct

     protected void init() {

         Resource resource = request.getResource() ;

     }

}

25 replies

New Participant
July 17, 2018

Yes, I tested this article and it works!! Below is the screenshot.

Hope this helps!!

Thanks,

Ratna Kumar.

smacdonald2008
New Participant
July 17, 2018

The doc example is wrong - the new HELPX artilce - follow it to learn how to extend core components - the Java part. You have to extend it as shown in the artilce. We are going to fix the example in the docs too to point to this new article. Ratna Kumar is currently testing this article.

rajeevy89244319
New Participant
July 17, 2018

Thanks Sam.

In helpx example, we are just using core title contract and then implementing the logic. In order to extend existing title implementation, what is recommended approach? Should we extended core implementation class or should we use @Via.

smacdonald2008
New Participant
July 17, 2018

For anyone reading this thread and want to know how to extend a Core Component - see this HELPX article -- Extending Adobe Experience Manager Core Components

smacdonald2008
New Participant
July 16, 2018

Here is a much better example to extend a Core Component - we will make a HELPX article -- use this to extend the Title COMPONENT. Notice here - they are not even using @Via

package com.adobe.community.core.models;

import javax.annotation.PostConstruct;

import org.apache.commons.lang3.StringUtils;

import org.apache.sling.api.SlingHttpServletRequest;

import org.apache.sling.models.annotations.Model;

import org.apache.sling.models.annotations.injectorspecific.InjectionStrategy;

import org.apache.sling.models.annotations.injectorspecific.ScriptVariable;

import org.apache.sling.models.annotations.injectorspecific.ValueMapValue;

import com.adobe.cq.wcm.core.components.models.Title;

import com.day.cq.commons.jcr.JcrConstants;

import com.day.cq.wcm.api.Page;

import com.day.cq.wcm.api.designer.Style;

@Model(resourceType = "/apps/ExtendCore/components/content/title",

    adaptables = SlingHttpServletRequest.class,

    adapters = Title.class)

public class MyCustomTitleImpl implements Title {

    @ScriptVariable

    private Page currentPage;

    @ScriptVariable

    private Style currentStyle;

    @ValueMapValue(injectionStrategy = InjectionStrategy.OPTIONAL, name = JcrConstants.JCR_TITLE)

    private String title;

    @ValueMapValue(injectionStrategy = InjectionStrategy.OPTIONAL)

    private String type;

    /**

     * The {@link Heading} object for the type of this title.

     */

    private Heading heading;

    @PostConstruct

    private void initModel() {

        if (StringUtils.isBlank(title)) {

            title = StringUtils.defaultIfEmpty(currentPage.getPageTitle(), currentPage.getTitle());

        }

        if (heading == null) {

            heading = Heading.getHeading(type);

            if (heading == null) {

                heading = Heading.getHeading(currentStyle.get(PN_DESIGN_DEFAULT_TYPE, String.class));

            }

        }

    }

    @Override

    public String getText() {

        return "My Project - " + title;

    }

    @Override

    public String getType() {

        if (heading != null) {

            return heading.getElement();

        }

        return null;

    }

    private enum Heading {

        H1("h1"),

        H2("h2"),

        H3("h3"),

        H4("h4"),

        H5("h5"),

        H6("h6");

        private String element;

        Heading(String element) {

            this.element = element;

        }

        private static Heading getHeading(String value) {

            for (Heading heading : values()) {

                if (StringUtils.equalsIgnoreCase(heading.element, value)) {

                    return heading;

                }

            }

            return null;

        }

        public String getElement() {

            return element;

        }

    }

}

rajeevy89244319
New Participant
July 16, 2018

Thanks Sam. I see.. you changed attribute resourceType to value for @via.. So documentation needs to be updated for correct attribute,

smacdonald2008
New Participant
July 16, 2018

I got it compiling with @Via

1st - i created a new Maven 13 Archetype project following this article: Creating an Adobe Experience Manager 6.4 Project using Adobe Maven Archetype 13

2nd added the new class to this project;  (NEVER ADD  A CLASS TO THE CORE COMPONENT PROJECT taken from Github). Always extend from a new AEM Java project. Here is full example:

package com.adobe.community.core.models;

import org.apache.sling.models.annotations.injectorspecific.Self;

import org.apache.sling.models.annotations.Via;

import org.apache.sling.api.resource.Resource;

import org.apache.sling.models.annotations.Default;

import org.apache.sling.models.annotations.Model;

import org.apache.sling.settings.SlingSettingsService;

import org.apache.sling.api.SlingHttpServletRequest;

import org.apache.sling.models.annotations.via.ResourceSuperType;

import com.adobe.cq.wcm.core.components.models.Breadcrumb;

@Model(adaptables = SlingHttpServletRequest.class,

       adapters = Breadcrumb.class,

       resourceType = "my-site/components/breadcrumb")

public class MyCustomBreadcrumbImpl implements Breadcrumb {

    /* ... */

    // get the default implementation for delegating

@Self @Via(value="core/wcm/components/breadcrumb/v2/breadcrumb", type=ResourceSuperType.class)

    private Breadcrumb delegate;

}

See:

3rd -add Core Components in POM

<dependency>

        <artifactId>core.wcm.components.core</artifactId>

        <version>2.0.4</version>

        <groupId>com.adobe.cq</groupId>

        <scope>provided</scope>

        </dependency>

(plus the UBER AEM JAR and others discussed in above article)

Finally -- if anyone wants to know more about the @Via annotation - see this Javadoc here - Apache Sling 9 API

smacdonald2008
New Participant
July 16, 2018

Yes - doc example looks wrong for sure. I am workign on this one. I am talking to the consulting team to see if we have a good KB articles on this as well. We will log a bug on the docs as @Via does not support what is shown in the docs.

rajeevy89244319
New Participant
July 16, 2018

I have tried with imports but getting error. For @Via, only type and value attributes are allowed. resourceType is invalid attribute. Not sure if it has to dependency bundle version mismatch.

smacdonald2008
New Participant
July 16, 2018

Problem with this code example in the AEM Docs is its missing import statements. I am adding them and will post back the version that compiles.