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AEM Cloud Service - Delegate Annotation for Extending AEM Core component Internal Sling Models | AEM Community Blog Seeding

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4/11/23

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AEM Cloud Service - Delegate Annotation for Extending AEM Core component Internal Sling Models by Sreekanth Choudry Nalabotu

Abstract

Goal
Sometimes everything provided by the Core Component Sling Models is just fine except you need a minor tweak. Say, you want alt of an image to show file name appended to alt text entered by user in dialog. Instead of creating a new sling model for the component and as you cannot extend the core component internal class com.adobe.cq.wcm.core.components.internal.models.v3.ImageImpl, create a delegate and override just the method you need eg. in this post public String getAlt()

Solution
1) Add Project Lombok Maven dependency in eaem-image-comp-sling-delegate\pom.xml


org.projectlombok
lombok
1.18.26
compile



2) Add sling model apps.experienceaem.sites.core.models.ImageAltDelegate for the component eaem-image-comp-sling-delegate/components/image and override just the public String getAlt() method...

package apps.experienceaem.sites.core.models;

import com.adobe.cq.export.json.ComponentExporter;
import com.adobe.cq.export.json.ExporterConstants;
import com.adobe.cq.wcm.core.components.models.Image;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.resource.Resource;
import org.apache.sling.models.annotations.Exporter;
import org.apache.sling.models.annotations.Model;
import org.apache.sling.models.annotations.Via;
import org.apache.sling.models.annotations.injectorspecific.InjectionStrategy;
import org.apache.sling.models.annotations.injectorspecific.Self;
import org.apache.sling.models.annotations.injectorspecific.SlingObject;
import org.apache.sling.models.annotations.injectorspecific.ValueMapValue;
import org.apache.sling.models.annotations.via.ResourceSuperType;
import lombok.experimental.Delegate;

@Model(
adaptables = {SlingHttpServletRequest.class},
adapters = {Image.class, ComponentExporter.class},
resourceType = { ImageAltDelegate.RESOURCE_TYPE }
)
@Exporter(name = ExporterConstants.SLING_MODEL_EXPORTER_NAME, extensions = ExporterConstants.SLING_MODEL_EXTENSION)
public class ImageAltDelegate implements Image {
public static final String RESOURCE_TYPE = "eaem-image-comp-sling-delegate/components/image";

@SlingObject
protected Resource resource;

@Self
@Via(type = ResourceSuperType.class)
@Delegate(excludes = DelegationExclusion.class)
private Image delegate;

@ValueMapValue(
name = "alt",
injectionStrategy = InjectionStrategy.OPTIONAL
)
protected String alt;

@ValueMapValue(
name = "fileReference",
injectionStrategy = InjectionStrategy.OPTIONAL
)
protected String fileReference;

@Override
public String getAlt() {
return delegate.getAlt() + "-" + fileReference.substring(fileReference.lastIndexOf("/") + 1);
}

private interface DelegationExclusion {
String getAlt();
}
}

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AEM Cloud Service - Delegate Annotation for Extending AEM Core component Internal Sling Models

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