Extending AEM Core Components

<!-- Hide "List Settings" tab inherited from core List component -->
<listSettings
    jcr:primaryType="nt:unstructured"
    sling:hideResource="{Boolean}true"/>

<!-- Hide "maxItems" field within an inherited tab -->
<maxItems
    jcr:primaryType="nt:unstructured"
    sling:hideResource="{Boolean}true"/>

<!-- Hide multiple fields at once -->
<items
    jcr:primaryType="nt:unstructured"
    sling:hideChildren="[maxItems,orderBy,childDepth,tags]"/>

<!-- Change inherited field label and make required -->
<title
    jcr:primaryType="nt:unstructured"
    sling:hideProperties="[fieldLabel,required,fieldDescription]"
    fieldLabel="Banner Title"
    fieldDescription="Enter the banner headline"
    required="{Boolean}true"/>

<customProperties
    jcr:primaryType="nt:unstructured"
    jcr:title="Custom Properties"
    sling:orderBefore="listSettings"
    sling:resourceType="granite/ui/components/coral/foundation/container"
    margin="{Boolean}true">
    <items jcr:primaryType="nt:unstructured">
        <!-- Custom fields here -->
    </items>
</customProperties>

package [package].models;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

import javax.annotation.PostConstruct;

import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.resource.Resource;
import org.apache.sling.models.annotations.DefaultInjectionStrategy;
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.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 com.adobe.cq.export.json.ComponentExporter;
import com.adobe.cq.export.json.ExporterConstants;

@Model(
    adaptables = SlingHttpServletRequest.class,
    adapters = {CustomComponentModel.class, ComponentExporter.class},
    resourceType = CustomComponentModel.RESOURCE_TYPE,
    defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL
)
@Exporter(
    name = ExporterConstants.SLING_MODEL_EXPORTER_NAME,
    extensions = ExporterConstants.SLING_MODEL_EXTENSION
)
public class CustomComponentModel implements ComponentExporter {

    public static final String RESOURCE_TYPE = "[project]/components/{component-name}";

    /**
     * Delegate to parent Core Component model via resourceSuperType.
     * Use fully qualified name to avoid import collisions.
     */
    @Self
    @Via(type = ResourceSuperType.class)
    private com.adobe.cq.wcm.core.components.models.ParentInterface coreComponent;

    /**
     * Access to current resource for reading child resources.
     */
    @SlingObject
    private Resource resource;

    /**
     * Custom property added by this extension.
     */
    @ValueMapValue
    private String customProperty;

    private List<CustomItem> customItems;

    @PostConstruct
    protected void init() {
        // Initialize custom multifield items
        customItems = new ArrayList<>();
        Resource itemsResource = resource.getChild("items");
        if (itemsResource != null) {
            for (Resource itemResource : itemsResource.getChildren()) {
                CustomItem item = itemResource.adaptTo(CustomItem.class);
                if (item != null && item.hasContent()) {
                    customItems.add(item);
                }
            }
        }
    }

    // Delegate inherited methods to parent
    public String getInheritedProperty() {
        return coreComponent != null ? coreComponent.getSomeProperty() : null;
    }

    // Custom property getters
    public String getCustomProperty() {
        return customProperty;
    }

    public List<CustomItem> getCustomItems() {
        return Collections.unmodifiableList(customItems);
    }

    public boolean hasContent() {
        return (customProperty != null && !customProperty.trim().isEmpty()) ||
               (customItems != null && !customItems.isEmpty()) ||
               coreComponent != null;
    }

    @Override
    public String getExportedType() {
        return RESOURCE_TYPE;
    }
}

// WRONG - Import collision error
import java.util.List;
import com.adobe.cq.wcm.core.components.models.List;  // ERROR!

// CORRECT - Use fully qualified name for Core Component interface
import java.util.List;  // Keep for collections

// In field declaration, use fully qualified name:
@Self
@Via(type = ResourceSuperType.class)
private com.adobe.cq.wcm.core.components.models.List coreList;

// 1. Add to adapters in @Model
@Model(
    adapters = {CustomModel.class, ComponentExporter.class},  // Add ComponentExporter
    ...
)

// 2. Add @Exporter annotation
@Exporter(
    name = ExporterConstants.SLING_MODEL_EXPORTER_NAME,
    extensions = ExporterConstants.SLING_MODEL_EXTENSION
)

// 3. Implement interface
public class CustomModel implements ComponentExporter {

    // 4. Implement required method
    @Override
    public String getExportedType() {
        return RESOURCE_TYPE;  // Must match @Model resourceType
    }
}