Interview Deck

Question 1

Explain the AEM stack (architecture).

Answer 1

Java Platform– AEM is a Java web application. It requires server-side Java Runtime Environment.

Granite Platform– Adobe’s open web stack. It forms the technical foundation on which AEM is built.

OSGi Framework– OSGi is dynamic software component system for Java. In this system, an application is composed of an assemblage of bundles that can be dynamically installed, started, stopped, and uninstalled without shutting down the application.

CQSE Servlet Engine– AEM includes the built-in CQSE servlet engine which runs as a bundle within the OSGi framework.

JCR Content Repository– CRX content repository is an implementation of Java Content Repository
Specification (JCR). All data within AEM is stored here.

Sling Content Delivery– AEM is built using Sling, a Web application framework based on REST principles that provides easy development of content-oriented applications. Sling uses CRX Content Repository as its data store.

AEM Modules– WCM, DAM, Workflow, etc.
Customer Applications– Websites that run on AEM.

Question 2

What are the major tech stack upgrades in AEM since CQ?

Answer 2

Jackrabbit Oak – offers improved performance and scalability compared to JCR

Sightly – new templating language that enforces separation of markup from logic and offers XSS protection

Touch UI – built using Coral UI framework, it supports touch enabled devices

Search– default search engine has been upgrade to Apache Solr

Question 3

What is headless AEM?

Answer 3

It allows content stored in the JCR to be retrieved and used without rendering the content within an AEM content page.

Question 4

What are the layers in OSGi?

Answer 4

Bundles– jar components with extra manifest headers

Services– holds the service-side of the framework;
keeps the service registry and manages it
Life-Cycle– manages and keeps track of the frameworks and bundles lifecycle state; used to install/uninstall framework objects and start/stop them
Modules– the bundle space; holds the bundles that are installed on the framework
Security– optional layer; when active, validates the bundle signatures and controls component access rights; extends the Java 2 security architecture
Execution Environment– bottom layer on which bundles live; selected to fit the underlying hardware or operating system

Question 5

What are the benefits of OSGi?

Answer 5

Reduced complexity - bundles hide internals, expose via services
Reuse - Modular code
Dynamic Updates - Easy deployment, keep the system running

Question 6

What are the differences between JAR and bundle?

Answer 6

Both have pom files
Jar:
  Packaging tag of "jar" in pom.xml 
  Consume by calling methods
Bundle:
  Used in OSGI runtime
  Packaging tag of "bundle" in pom.xml
  Consume by calling services
  Bundle is a jar with extra manifest headers.

Question 7

What are the differences between package and bundle?

Answer 7

Both have pom files

Package:

Contains content, files, or even other bundles
Deployed into the Package Manager
Packaging tag of “content-package” in pom.xml

Bundles:

Jar with extra manifest headers
Install via Felix Console
Packaging tag of “bundle” in pom.xml

Question 8

How do you install an OSGi bundle using the CRX repository?

Answer 8

Copy the bundle into the /apps/install folder.***

Create the project directory, then install the bundle from the package manager

Question 9

What is REST principle?

Answer 9

Uniform Interface– individual resources are identified using URLs but are different from the representation sent to the client
Stateless Interactions– none of the clients context is to be stored on server side between request; all necessary information to service the request is contained in URL, query parameters, body, or headers
Cacheable– clients can cache the responses, but only on those defined as cacheable to prevent client from sending inappropriate data
Client-Server– clients and server are separated from each other and neither side is concerned with the other.
Layered System– client cannot tell if it’s connect to the end server or intermediate; intermediate layer helps enforce security policies and enable load-balancing
Code on Demand– optional constraint where server temporarily extends functionality of a client by the transfer of executable code

Question 10

Differences between REST and SOAP.

Answer 10

REST:

Representational State Transfer
Uses URI for business logic
Is architectural style
Inherits security measures

SOAP:

Simple Object Access Protocol
Uses service inference for business logic
Uses own security
Only XML data

Question 11

Describe the Apache Sling script resolution process.

Answer 11

HTTP Request
Content resolution
Get resource type
Locate script
Match script
Include options.
Execute script.

Question 12

What is a sling model?

Answer 12

Sling models are annotation driven POJOs (Plain ol’ Java Object) which are mapped automatically from Sling objects like resources, request objects and OSGI services. The use of annotations helps reduce complexity/lines of code.

Declared with @Model(adaptables = Resource.class)

Question 13

Explain how sling is content-centric.

Answer 13

Each HTTP request is mapped onto content in the form of a resource node, instead of static file path resolution.

Question 14

What are the commonly used Sling APIs?

Answer 14

ValueMap – easy way to access a resource’s properties
ResourceResolver– defines service API which may be used to resolve Resource objects
ResourceResolverFactory - used to access ResourceResolver instances
ResourceProvider– API for providers of resources
Resource– pieces of content on which Sling acts; an Adaptable to get adapters to other types
ResourceWrapper– wrapper for any Resource delegating all method calls to the wrapped resource by default
ResourceUtil– provides helper methods for dealing with resources

Question 15

Do you use JCR or Sling Resource API to update individual resources, and why?

Answer 15

JCR is lower level and slightly faster, but Sling is higher level which makes it more abstract and easier to code.

Best practice is to use higher level apis when possible.

Question 16

After updating the resource using Sling Resource API, what must you do to finish?

Answer 16

Commit the changes and close the resource resolver.

Question 17

Which provider service scans CRX repository for artifacts and provides them to the OSGi installer?

Answer 17

Sling JCR Installer

Question 18

What is the JCR?

Answer 18

Java Content Repository - Content repository that combines features of the traditional relational database with those of a conventional file system:

Hierarchy– content can be addressed by path
Semi-structured content– can store structured documents, like XML, (which can have variable fields)
Access Control and Locking– can restrict access to different parts of the content hierarchy based on policies or ACLs; also supports locking of content to prevent conflicts

Question 19

What kind of indexing does AEM now use?

Answer 19

Oak indexing which is not enabled by default. AEM also supports:
Solr
Apache Lucene
Property Index
Traversal Index

Question 20

You want to install bundles through CRX only in the author instance. Which folder name can you use for that purpose?

Answer 20

install.author

Question 21

You want to request a JSON representation of the content. What do you have to do with the request?

Answer 21

Change the extension to .json

Question 22

Why we need TAR Compaction?

Answer 22

If we are using Tar files as the storage, it tends to grow in size and starts claiming disk space every time when data is created or updated as data in tar files are never overwritten rather it keeps adding new versions. To mitigate the same, AEM has garbage collection mechanism which is known as ‘Tar Compaction’ to remove the unused data and reclaim the disk space.

Question 23

Explain David’s content model.

Answer 23

David Model:

Data First, Structure Later. Maybe.
Drive the content hierarchy, don’t let it happen.
Workspaces are good for versioned JCR projects.
Beware of Same Name Siblings.
References considered harmful.
Files are Files.
IDs are evil.

Question 24

What’s the difference between Event Handler and Event Listener?

Answer 24

EventHandler:
Used at the Sling level
Watches for Sling properties?

EventListener:
Used at the JCR level
Watches for node changes

Question 25

What is the difference between Live Copy and Language Copy?

Answer 25

Live Copy Copy of specific site content which automatically updates along with the original source Inherits content from its source page Use if you intend to reuse content at multiple locations Language Copy Copy of an existing site that is to be translated to another language; no live relationship One time copy of the content Use if you intend to translate content

Question 26

If you are creating a site with multiple locales that must be synchronized, which should you pick and why?

Answer 26

Use Language Copy. While it does not have the same live relationship that Live Copy has, you can update the Language Copy. Use Update & Translate workflows to synchronize changes between the source and language copy.

Question 27

What are Rollout Configurations?

Answer 27

Rules/instructions that determine which properties will be synchronized/always carried out on a deployment, how and when.

Question 28

What is workflow?

Answer 28

Workflows are designed to coordinate and automate steps needed to complete a task. It can automate experience manager activities and interact with AEM assets.

Question 29

What are the different types of steps present in workflow?

Answer 29

Process step – executes an ECMA script or calls an OSGi service to perform automatic processing Participant step – enables you to assign ownership for a particular action; requires the owner to manually acknowledge the step Container step – starts another workflow model that executes as a child workflow OR, AND, and GOTO Split Step – Logical operator branching steps

Question 30

What are examples of inbuilt workflow present in AEM?

Answer 30

DAM MetaData Writeback – This workflow manages XMP write-back to the original binary and sets the last modified date in jcr. To propogate metadata changes to select renditions of the asset, add the name of the renditions to the XMP Writeback Process workflow step of DAM Metadata WriteBack workflow. By default, this step is configured with the original rendition. Approve for Adobe Campaign – Workflow handling the edition, review and approval of a newsletter to be sent using Adobe Campaign. DAM Update Asset – By default, upon image upload to DAM, one of the many processes inside this workflow is to generate a web rendition of the uploaded image. The default setting of CQ's Image API is to always render the web-enabled version of the uploaded image. This combination helps to limit the size and quality of the image displayed, thus reducing the page load time. Download Asset DAM Parse Word Document

Question 31

What is dialog, design dialog, and cq:dialog?

Answer 31

``` cq:dialog: Page level configuration TouchUI name = cq:dialog Stored under page's jcr:content Get value from properties object jcr:primaryType is nt:unstructured ``` ``` dialog: Page level configuration Classic UI name = dialog Stored under page's jcr:content Get value from properties object jcr:primaryType is cq:Dialog ``` ``` design_dialog: Template level configuration Design Mode name = design_dialog Stored under design page located under /etc/design/default Get value from currentStyle object jcr:primaryType is cq:Dialog ```

Question 32

What is the use of the EditConfig node?

Answer 32

EditConfig nodes are used to edit the configuration of components. Examples include adding properties, child nodes, listeners, and customizing the layout.

Question 33

What is the difference between sling:resourceSuperType and sling:resourceType?

Answer 33

sling: resourceSuperType – used to achieve resource type inheritance from the specified component sling: resourceType – primary resource type used to render content; absolute or relative path used to locate the script

Question 34

How do you extend an OOTB component?

Answer 34

Add the property "sling:superResourceType" to your custom component's node with the value of the component you want to inherit

Question 35

What are overlays?

Answer 35

Overlaying is the process of globally overriding the out of the box components. This is done by copying the node structure and replicating it under /apps, and allows for easy enhancements

Question 36

What is the difference between overlaying and extending a component?

Answer 36

Overlaying – Globally overriding an out of the box component by copying its contents into the /apps folder. Allows for easy enhancements Extending – A custom component that's built to inherit from another out of the box component using the sling:superResourceType property

Question 37

Difference between parsys and iparsys.

Answer 37

parsys – It is a placeholder called “Paragraph System”, where we can drag and drop or add other components or scripts at page level. iparsys - The inherited paragraph system is a paragraph system that also allows you to inherit the created paragraphs from the parent. it is similar to parsys except that it allows to inherits parent page “paragraph system” at template level. You can also cancel paragraph inheritance at a level at any time. It has two checkbox options to cancel/disable the inheritance. Cancel Inheritance - If selected, the components in this paragraph system are not passed down to the child pages. Disable Inheritance - If selected, components of this paragraph system on this page are not inherited from the parent page.

Question 38

What is parbase?

Answer 38

Parbase is a key component as it allows components to inherit attributes from other components.

Question 39

Difference between jcr:primaryType and jcr:mixinTypes

Answer 39

jcr: primaryType - Required on initial creation and is the user defined node type, sort of like a class in Java. jcr: mixinTypes - An additional type that exists in addition to the primaryType and supports additional properties/child nodes.

Question 40

Difference between allowedPaths, allowedChildren and allowedParents?

Answer 40

allowedPaths - Path of a page that is allowed to be based on this template. allowedChildren - Path of a template that is allowed to be a child of this template. allowedParents - Path of a template that is allowed to be a parent of this template.

Question 41

What is componentGroup, cq:isContainer and cq:noDecoration property?

Answer 41

componentGroup - Group under which the component can be selected in the Sidekick. cq: isContainer - Checks if this component is a container component. For example a paragraph system component. cq: noDecoration - If true, the component is not rendered with automatically generated div and css classes.

Question 42

What is serviceFactory?

Answer 42

An OSGi service factory is a special class ServiceFactory, which can create individual instances of service objects for different bundles. Sometimes a service needs to be differently configured depending on which bundle uses the service. For example, the log service needs to be able to print the logging bundle’s id, otherwise the log would be hard to read.

Question 43

What are advantages of services?

Answer 43

``` Separates interface from implementation Lookup is based on Interface name Direct method invocation Good design practice Enables reuse, substitutability, loose coupling and late binding. ```

Question 44

How do you create a service class?

Answer 44

@component - defines the class as a component @service - defines the service interface that is provided by the component

Question 45

What are the annotations used in OSGi?

Answer 45

@Component - annotates an implementation class and is used to declare it as a component type. It is the only required annotation. If this annotation is not declared for a Java class, the class is not declared as a component. @Service - defines whether and which service interfaces are provided by the component. This is a class annotation. @Reference - defines references to other services made available to the component by the Service Component Runtime. @Property - defines properties which are made available to the component through the ComponentContext.getProperties() method. These tags are not strictly required but may be used by components to defined initial configuration. Additionally properties may be set here to identify the component if it is registered as a service, for example the service.description and service.vendor properties.

Question 46

What are the difference between OSGI components and services?

Answer 46

Component - Components can't reference other components, they can only reference services. Components are consumers Service - Services are components but they provide function to components and can be injected into them. Services are providers

Question 47

How do you call a service?

Answer 47

Use SCR annotations to let SCR inject the service in your component:(Generally in Servlet)      @Reference       private MyService myService; Use sling.getService() method(Generally in JSP)       MyService service=sling.getService(MyService.class); ``` Use SlingScriptHelper.getService() method (into Java Use-API class ie Handler class )       MyService service=getSlingScriptHandler().getService(MyService.class); ```

Question 48

What is ServiceFactory?

Answer 48

It's a class that can create individual instances of service objects for different bundles.

Question 49

What is a PID?

Answer 49

The PID is a globally unique string that can be used to identify services in the Felix console

Question 50

How to register a servlet using Java annotations?

Answer 50

There are two ways. Use @SlingServlet annotation Use @Property(name = "sling.servlet.resourceTypes", value = "sling/servlet/default") Both define the values of the properties resourceTypes, selectors, extensions, and methods

Question 51

How do you register a servlet in AEM?

Answer 51

There are two standard approaches. By path @SlingServlet( paths={"/bin/customservlet/path"} ) By resourceType @SlingServlet( resourceTypes = "sling/servlet/path") If the path property is set, the resourceType property is ignored.

Question 52

What is the difference between binding a Servlet by resource type rather than paths?

Answer 52

By resourcetype: Registering a Servlet by resource type is the preferred approach in Sling in order to wire rendering logic to requested resources ("resource comes first" approach) Access to JCR ACLs Suffix handling By path: Statically mapped to a path Paths need to be explicitly allowed

Question 53

Why configure a Sling Servlet to be called on a resource type instead of a path?

Answer 53

The path may be impacted by dispatcher rules around permissions. A resource type allows for Sling inheritance. Access to JCR ACLs Suffix handling

Question 54

How to get session in Servlet?

Answer 54

There are two approaches. Get session from SlingHttpServletRequest. Session session = slingHttpServletRequest.getResourceResolver().adaptTo(Session.class) Get session from ResourceResolverFactory. resolver = resourceResolverFactory.getServiceResourceResolver(param); Session session = resolver.adaptTo(Session.class);

Question 55

What is a Resource object?

Answer 55

Resources are pieces of content on which Sling acts

Question 56

What is ResourceResolver object?

Answer 56

The ResourceResolver defines the service API which may be used to resolve Resource objects.

Question 57

What is a Session object?

Answer 57

The Session object provides read and write access to the content of a particular workspace in the repository.

Question 58

What is a client library?

Answer 58

A library for your clients A feature of AEM that allows you to manage client side resources like Javascript, CSS, images, fonts etc... It also allows for debugging, minifying, and merging client-side code.

Question 59

How do you debug client library files in a web browser?

Answer 59

Add this to the end of your URL: ?debugClientLibs=true

Question 60

How do you rebuild client libraries?

Answer 60

Yes, via url: /libs/granite/ui/content/dumplibs.rebuild.html, we can invalidate or rebuild the clientlibs.

Question 61

Is there a console where I can see all client libraries and their dependencies?

Answer 61

Yes: http://server/libs/cq/ui/content/dumplibs.html

Question 62

What are categories, dependencies, embed and allowProxy properties in AEM?

Answer 62

Categories - the list of identifiers to publish a clientlib under Dependencies - specifies other client libraries the current one depends on (causes your page to have extra requests to other clientlibs) embed - Embeds code from other libraries into the current one. If node F embeds nodes G and H, the resulting HTML will be a concatenation of content from nodes G and H. allowProxy - If a client library is located under /apps, this property allows access to it via proxy servlet.

Question 63

Where are the generated client library files stored/cached in CQ?

Answer 63

They are in /var/clientlibs

Question 64

If the builds were being deployed manually, what would you suggest as a change?

Answer 64

Set up Jenkins to use for automated deployments.

Question 65

What is the dispatcher?

Answer 65

Dispatcher is AEM's caching and/or load balancing tool. It essentially acts like a reverse proxy server, fielding http requests from a client (typically a web browser) and sending responses back

Question 66

Have you seen the dispatcher used with any web server other than Apache? For example, nginx.

Answer 66

(Answer will vary depending on experience)

Question 67

What is Sightly/HTL?

Answer 67

HTL stands for HTML Template Language and is was formerly known as Sightly. It was introduced in AEM 6.0 and takes the place of JSP.

Question 68

What is advantages of sightly/HTML Template Language?

Answer 68

Increased Security - HTL is well protected against cross site scripting (XSS) by having HTML tag context-aware escaping of variables to prevent injection. Simplified Development - Its features are purposely limited to ensure that it stays simple and straight-forward. Wider range of implicit objects as compared to JSP. Reduced Costs - Increased security, simplified development and improved team collaboration, translates for AEM projects in reduced effort, faster time to market (TTM), and lower total cost of ownership (TCO).

Question 69

What are the Use-API in sightly?

Answer 69

Java Use-API - Enables an HTL file to access helper methods in a custom Java class. This allows all complex business logic to be encapsulated in the Java code, while the HTL code is embedded into the HTML JavaScript Use-API - Enables an HTL file to access helper code written in JavaScript. This allows all complex business logic to be encapsulated in the JavaScript code, while the HTL code is embedded into the HTML

Question 70

What is the use of unwrap in sightly?

Answer 70

Unwrap attribute - Remove the outer elements (i.e. HTML Tags) leaving just the output of the expression

Question 71

What are the implicit objects present in sightly?

Answer 71

Enumerable Objects: properties: properties of the current resource pageProperties: properties of the current page inheritedPageProperties: inherited properties of the current page ``` Java-backed Objects: component currentDesign currentPage request resource resourceDesign resourcePage wcmmode ```

Question 72

Are you a back-end, front-end, or full-stack developer? What is a typical development process and how do you fit in?

Answer 72

A creative design team typically provides wireframes and design comps. A front-end developer slices-and-dices the comps into front-end code (HTML, CSS, and javascript), often after discussing with an AEM Lead howt o break down a page into modular components (to determine what is part of each component on a page and what can be leveraged across multiple pages) A back-end AEM developer creates template, component stubs, and skeletons. A front-end or back-end developer gets the front-end code into AEM. A back-end developer implements Sling Models, OSGi components, and any other back-end functionality needed. A developer implements any authoring functionality needed (e.g. component dialogs, customizations to OOTB AEM authoring tools).

Question 73

How do you create a login functionality?

Answer 73

Submit button POST form / ajax Verify against user table Return request

Question 74

What technology have you worked on in AEM?

Answer 74

(Your answer will vary depending on your own experience.)

Question 75

What workflows or event handlers have you developed?

Answer 75

(Your answer will vary depending on your own experience.)

Question 76

What OSGi services have you worked on?

Answer 76

(Your answer will vary depending on your own experience.)

Question 77

Explain the changes in AEM 6.4 for Sling model.

Answer 77

Sling nested multi-fields

Question 78

Define what a Template is in AEM

Answer 78

A template enables you to define a consistent style for the pages in your application. A template is comprised of nodes that specify the page structure.

Question 79

Where is the content stored from cq:dialog or dialog nodes?

Answer 79

Design dialog data is stored under /etc./designs folder. | Dialog data is stored under /content folder.

Question 80

What is REST?

Answer 80

It's the representational State Transfer architecture. It provides interoperability between computer systems on the internet in a loosely coupled fashion.