AEM Component Development

AEM components are the building blocks of page content. Each component is a cq:Component node in the JCR that ties together:

1. HTL markup — the rendering template (.html file)
2. Sling Model — server-side business logic (Java)
3. Dialog — author UI for content editing (cq:dialog)
4. Client libraries — CSS/JS for frontend behavior
5. Edit config — authoring toolbar behavior (cq:editConfig)

Prerequisite skill: This skill assumes HTL knowledge. Load the htl-scripting skill for expression syntax, block statements, XSS contexts, and global objects.

Component File Structure

Standard Maven archetype layout (Touch UI, modern AEM):

ui.apps/src/main/content/jcr_root/apps/<project>/components/<component-name>/
├── .content.xml          ← cq:Component definition (title, group, supertype)
├── <component-name>.html ← HTL rendering script
├── _cq_dialog/
│   └── .content.xml      ← Touch UI dialog (Granite UI)
├── _cq_editConfig/
│   └── .content.xml      ← Edit behavior config
├── _cq_template/
│   └── .content.xml      ← Default content on drag-and-drop
├── _cq_design_dialog/
│   └── .content.xml      ← Policy/design dialog
└── clientlib/             ← Optional co-located clientlib
    ├── .content.xml
    ├── css.txt
    ├── js.txt
    ├── css/
    └── js/

core/src/main/java/<package>/models/
└── <ComponentName>Model.java  ← Sling Model

Note: Underscored directories (_cq_dialog) are the filesystem representation of JCR nodes with colons (cq:dialog). The FileVault serialization requires this naming.

Component Definition (.content.xml)

<?xml version="1.0" encoding="UTF-8"?>
<jcr:root xmlns:cq="http://www.day.com/jcr/cq/1.0"
          xmlns:jcr="http://www.jcp.org/jcr/1.0"
    jcr:primaryType="cq:Component"
    jcr:title="My Component"
    jcr:description="A description for authors"
    componentGroup="My Project - Content"
    sling:resourceSuperType="core/wcm/components/text/v2/text"/>

Key Properties

Agent Workflow: Creating a New Component

Step 1: Define the component node

Create .content.xml with jcr:primaryType="cq:Component", title, group, and optionally sling:resourceSuperType to extend an existing component.

Step 2: Create the Sling Model

Write the Java model class in core/ module. See references/sling-models.md.

@Model(adaptables = SlingHttpServletRequest.class,
       adapters = MyComponent.class,
       resourceType = "myproject/components/mycomponent",
       defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)
public class MyComponentImpl implements MyComponent {

    @ValueMapValue
    private String title;

    @ValueMapValue
    private String description;

    @Override
    public String getTitle() { return title; }

    @Override
    public String getDescription() { return description; }
}

Step 3: Create the HTL script

<sly data-sly-use.model="com.myproject.core.models.MyComponent"/>
<div class="cmp-mycomponent"
     data-sly-test="${model.title || model.description}">
    <h2 class="cmp-mycomponent__title"
        data-sly-test="${model.title}">${model.title}</h2>
    <div class="cmp-mycomponent__description"
         data-sly-test="${model.description}">
        ${model.description @ context='html'}
    </div>
</div>
<sly data-sly-test="${!model.title && !model.description && (wcmmode.edit || wcmmode.preview)}">
    <div class="cq-placeholder" data-emptytext="My Component"></div>
</sly>

Step 4: Create the dialog

See references/dialogs.md for full Granite UI field reference.

<?xml version="1.0" encoding="UTF-8"?>
<jcr:root xmlns:sling="http://sling.apache.org/jcr/sling/1.0"
          xmlns:cq="http://www.day.com/jcr/cq/1.0"
          xmlns:jcr="http://www.jcp.org/jcr/1.0"
          xmlns:nt="http://www.jcp.org/jcr/nt/1.0"
    jcr:primaryType="nt:unstructured"
    jcr:title="My Component"
    sling:resourceType="cq/gui/components/authoring/dialog">
    <content jcr:primaryType="nt:unstructured"
             sling:resourceType="granite/ui/components/coral/foundation/container">
        <items jcr:primaryType="nt:unstructured">
            <tabs jcr:primaryType="nt:unstructured"
                  sling:resourceType="granite/ui/components/coral/foundation/tabs"
                  maximized="{Boolean}true">
                <items jcr:primaryType="nt:unstructured">
                    <properties jcr:primaryType="nt:unstructured"
                                jcr:title="Properties"
                                sling:resourceType="granite/ui/components/coral/foundation/container"
                                margin="{Boolean}true">
                        <items jcr:primaryType="nt:unstructured">
                            <columns jcr:primaryType="nt:unstructured"
                                     sling:resourceType="granite/ui/components/coral/foundation/fixedcolumns"
                                     margin="{Boolean}true">
                                <items jcr:primaryType="nt:unstructured">
                                    <column jcr:primaryType="nt:unstructured"
                                            sling:resourceType="granite/ui/components/coral/foundation/container">
                                        <items jcr:primaryType="nt:unstructured">
                                            <title jcr:primaryType="nt:unstructured"
                                                   sling:resourceType="granite/ui/components/coral/foundation/form/textfield"
                                                   fieldLabel="Title"
                                                   name="./title"/>
                                            <description jcr:primaryType="nt:unstructured"
                                                         sling:resourceType="granite/ui/components/coral/foundation/form/textarea"
                                                         fieldLabel="Description"
                                                         name="./description"/>
                                        </items>
                                    </column>
                                </items>
                            </columns>
                        </items>
                    </properties>
                </items>
            </tabs>
        </items>
    </content>
</jcr:root>

Step 5: Add client library (if needed)

See references/clientlibs.md.

Step 6: Configure edit behavior (if needed)

<?xml version="1.0" encoding="UTF-8"?>
<jcr:root xmlns:cq="http://www.day.com/jcr/cq/1.0"
          xmlns:jcr="http://www.jcp.org/jcr/1.0"
    jcr:primaryType="cq:EditConfig"
    cq:actions="[edit,delete,insert,copymove]"
    cq:layout="editbar"
    cq:dialogMode="floating">
    <cq:listeners jcr:primaryType="cq:EditListenersConfig"
                  afteredit="REFRESH_PAGE"
                  afterinsert="REFRESH_PAGE"/>
</jcr:root>

Extending Existing Components

Use sling:resourceSuperType to inherit everything from a parent:

<jcr:root ...
    jcr:primaryType="cq:Component"
    jcr:title="Custom Text"
    sling:resourceSuperType="core/wcm/components/text/v2/text"
    componentGroup="My Project"/>

What you inherit automatically:

• HTL rendering scripts (resolved by Sling resource type hierarchy)
• Dialogs (can overlay individual fields via Sling Resource Merger)
• Edit config, descriptions, icons

To overlay a dialog field, create only the nodes you need to change under _cq_dialog/ and set sling:resourceSuperType on the dialog root. The Sling Resource Merger merges your changes with the parent.

Core Components

Always prefer extending AEM Core Components over building from scratch. They provide:

• Production-tested, accessible, SEO-friendly markup
• BEM CSS class naming (cmp-<name>__<element>--<modifier>)
• Sling Model exporters for JSON/SPA
• Style System support
• Adobe Client Data Layer integration

Common Core Components to extend:

• core/wcm/components/text/v2/text
• core/wcm/components/image/v3/image
• core/wcm/components/title/v3/title
• core/wcm/components/teaser/v2/teaser
• core/wcm/components/list/v4/list
• core/wcm/components/container/v1/container
• core/wcm/components/page/v3/page

Edit Placeholder Pattern

Components MUST render something visible in edit mode even when empty:

<!--/* Reusable Core Components placeholder template */-->
<sly data-sly-use.template="core/wcm/components/commons/v1/templates.html"
     data-sly-call="${template.placeholder @ isEmpty=!model.hasContent}"/>

Or manual fallback:

<div class="cq-placeholder" data-emptytext="${component.properties.jcr:title}"
     data-sly-test="${(wcmmode.edit || wcmmode.preview) && isEmpty}"></div>

Content Template (_cq_template/)

Pre-populates the component's content node when dragged onto a page:

<?xml version="1.0" encoding="UTF-8"?>
<jcr:root xmlns:jcr="http://www.jcp.org/jcr/1.0"
    jcr:primaryType="nt:unstructured"
    title="Default Title"
    description="Edit this component"/>

Resource Type Resolution

Sling resolves components by sling:resourceType on the content node:

1. Content node has sling:resourceType = "myproject/components/hero"
2. Sling looks for /apps/myproject/components/hero/hero.html
3. If not found, checks sling:resourceSuperType chain
4. Falls back to /libs/ search path

Script resolution order for a resource type myproject/components/hero:

1. hero.html (matches component name)
2. html.html (matches extension)
3. GET.html (matches method + extension)
4. Then walks up the sling:resourceSuperType chain

Critical Rules

1. Always use Touch UI (cq:dialog) — Classic UI dialogs are deprecated.
2. Prefer Sling Models over WCMUsePojo — Sling Models are testable, cacheable, and the standard for AEM as a Cloud Service.
3. Never modify /libs — always overlay in /apps. Use Sling Resource Merger for partial overrides.
4. Always render an edit placeholder when component has no content.
5. Use BEM naming for CSS classes: cmp-<component>__<element>--<modifier>.
6. Set componentGroup or the component won't appear in the authoring UI.
7. Store dialog field values with ./ prefix in name attribute (e.g., name="./title") to write relative to the component's content node.
8. Extend Core Components before building from scratch.
9. Client libraries under /apps need allowProxy=true to be served via /etc.clientlibs/.

Reference Files

• references/dialogs.md — Touch UI dialog structure, Granite UI field types, tabs, validation
• references/clientlibs.md — Client library folder setup, categories, dependencies, HTL inclusion
• references/sling-models.md — Sling Model annotations, injection strategies, adapters, testing