Using Client-Side Libraries on AEM as a Cloud Service using-client-side-libraries

Digital experiences rely heavily on client-side processing driven by complex JavaScript and CSS code. AEM Client-Side Libraries (clientlibs) allow you to organize and centrally store these client-side libraries within the repository. Coupled with the front-end build process in the AEM Project archetype, managing your front-end code for your AEM project becomes simple.

Advantages of using clientlibs in AEM include:

Clientlibs are the built-in solution for delivering CSS and JavaScript from AEM.

What Are Client-Side Libraries what-are-clientlibs

Sites require JavaScript and CSS and static resources such as icons and web fonts to be processed client-side. A clientlib is AEM’s mechanism to reference (by category if necessary) and serving such resources.

AEM collects the site’s CSS and JavaScript into a single file, in a central location, to ensure that only one copy of any resource is included in the HTML output. This maximizes the efficiency of delivery and allows such resources to be maintained centrally in the repository via proxy, keeping access secure.

Front-End Development for AEM as a Cloud Service fed-for-aemaacs

All JavaScript, CSS, and other front-end assets should be maintained in the ui.frontend module of the AEM Project Archetype. The flexibility of the archetype lets you use your modern web tools of choice to create and manage these resources.

The archetype can then compile the resources into single CSS and JS files, embedding them automatically into a cq:clientLibraryFolder in the repository.

Client-Side Library Folder Structure clientlib-folders

A client-side library folder is a repository node of type cq:ClientLibraryFolder. Its definition in CND notation is

[cq:ClientLibraryFolder] > sling:Folder
  - dependencies (string) multiple
  - categories (string) multiple
  - embed (string) multiple
  - channels (string) multiple

Each cq:ClientLibraryFolder is populated with a set of JS and/or CSS files, along with a few supporting files (see below). Important properties of the cq:ClientLibraryFolder are configured as follows:

If the client library folder contains one or more source files that, at runtime, they are merged into a single JS and/or CSS file. The name of the generated file is the node name with either the .js or .css file name extension. For example, the library node named cq.jquery results in the generated file named cq.jquery.js or cq.jquery.css.

Client library folders contain the following items:

Creating Client-Side Library Folders creating-clientlib-folders

Client libraries must be located under /apps. This rule necessary to better isolate code from content and configuration.

In order for the client libraries under /apps to be accessible, a proxy servelt is used. The ACLs are still enforced on the client library folder, but the servlet allows for the content to be read via /etc.clientlibs/ if the allowProxy property is set to true.

Serving Client-Side Libraries serving-clientlibs

Once your client library folder is configured as required, your clientlibs can be requested via proxy. As an example:

The allowProxy property lets you request:

Loading Client Libraries via HTL loading-via-htl

Once your clientlibs are successfully stored and managed in their client library folder, they can be access via HTL.

Client libraries are loaded through a helper template provided by AEM, which can be accessed through data-sly-use. Helper templates are available in this file, which can be called through data-sly-call.

Each helper template expects a categories option for referencing the desired client libraries. That option can be either an array of string values, or a string containing a comma separated values list.

See the HTL documentation for more details on loading clientlibs via HTL.

Client Libraries on Author versus Publish clientlibs-author-publish

Most clientlibs are required on the AEM publish instance. That is, most clientlibs’ purposes are to produce the end-user experience of the content. For clientlibs on publish instances, front-end build tools can be used and deployed via client library folders as described above.

However there are times when client libraries may be necessary to customize the authoring experience. For example, customizing a dialog might require deploying small bits of CSS or JS to the AEM authoring instance.

Managing Client Libraries on Author clientlibs-on-author

If you need to use client libraries on author, you can create your client libraries under /apps using the same methods as for publish, but write it directly under /apps/.../clientlibs/foo instead of creating an entire project to manage it.

You can then “hook” into the authoring JS by adding your client libraries to an out-of-the-box client library category.

Debugging Tools debugging-tools

AEM provides several tools for debugging and testing client library folders.

Discover Client Libraries discover-client-libraries

The /libs/cq/granite/components/dumplibs/dumplibs component generates a page of information about all client library folders on the system. The /libs/granite/ui/content/dumplibs node has the component as a resource type. To open the page, use the following URL (changing the host and port as required):

https://<host>:<port>/libs/granite/ui/content/dumplibs.test.html

The information includes the library path and type (CSS or JS), and the values of the library attributes, such as categories and dependencies. Subsequent tables on the page show the libraries in each category and channel.

See Generated Output see-generated-output

The dumplibs component includes a test selector that displays the source code that is generated for ui:includeClientLib tags. The page includes code for different combinations of js, css, and themed attributes.

Additional Client Library Folder Features additional-features

There are several other features that are supported by client library folders in AEM. However, these are not required on AEM as a Cloud Service and as such their use is discouraged. They are listed here for completeness.

Adobe Granite HTML LIbrary Manager html-library-manager

Additional client library settings can be controlled through the Adobe Granite HTML Library Manager panel of the System Console at https://<host>:<port>/system/console/configMgr).

Additional Folder Properties additional-folder-properties

Additional folder properties include allow control of dependencies and embeds, but are generally no longer needed and their use is discouraged:

Linking to Dependencies linking-to-dependencies

When the code in your client library folder references other libraries, identify the other libraries as dependencies. The ui:includeClientLib tag that references your client library folder causes the HTML code to include a link to your generated library file and the dependencies.

The dependencies must be another cq:ClientLibraryFolder. To identify dependencies, add a property to your cq:ClientLibraryFolder node with the following attributes:

For example, the /etc/clientlibs/myclientlibs/publicmain has a dependency on the cq.jquery library. The page that references the main client library generates HTML that includes the following code:

<script src="/etc/clientlibs/foundation/cq.jquery.js" type="text/javascript">
<script src="/etc/clientlibs/mylibs/publicmain.js" type="text/javascript">

Embedding Code From Other Libraries embedding-code-from-other-libraries

You can embed code from a client library into another client library. At runtime, the generated JS and CSS files of the embedding library includes the code of the embedded library.

Embedding code is useful for providing access to libraries that are stored in secured areas of the repository.

App-Specific Client Library Folders app-specific-client-library-folders

It is a best practice to keep all application-related files in their application folder below /apps. It is also a best practice to deny access for web site visitors to the /apps folder. To satisfy both best practices, create a client library folder below the /etc folder that embeds the client library that is below /apps.

Use the categories property to identify the client library folder to embed. To embed the library, add a property to the embedding cq:ClientLibraryFolder node, using the following property attributes:

Using Embedding to Minimize Requests using-embedding-to-minimize-requests

In some cases you may find that the final HTML generated for typical page by your publish instance includes a relatively large number of <script> elements.

In such cases, it can be useful to combine all the required client library code in to a single file so that the number of back and forth requests on page load is reduced. To do this you can embed the required libraries into you app-specific client library using the embed property of the cq:ClientLibraryFolder node.

Paths in CSS Files paths-in-css-files

When you embed CSS files, the generated CSS code uses paths to resources that are relative to the embedding library. For example, the publicly-accessible library /etc/client/libraries/myclientlibs/publicmain embeds the /apps/myapp/clientlib client library:

The main.css file contains the following style:

body {
  padding: 0;
  margin: 0;
  background: url(images/bg-full.jpg) no-repeat center top;
  width: 100%;
}

The CSS file that the publicmain node generates contains the following style, using the URL of the original image:

body {
  padding: 0;
  margin: 0;
  background: url(../../../apps/myapp/clientlib/styles/images/bg-full.jpg) no-repeat center top;
  width: 100%;
}

See Embedded Files in HTML Output see-embedded-files

To trace the origin of embedded code, or to ensure that embedded client libraries are producing the expected results, you can see the names of the files that are being embedded at runtime. To see the file names, append the debugClientLibs=true parameter to the URL of your web page. The library that is generated contains @import statements instead of the embedded code.

In the example in the previous Embedding Code From Other Libraries section, the /etc/client/libraries/myclientlibs/publicmain client library folder embeds the /apps/myapp/clientlib client library folder. Appending the parameter to the web page produces the following link in the web page’s source code:

<link rel="stylesheet" href="/etc/clientlibs/mycientlibs/publicmain.css">

Opening the publicmain.css file reveals the following code:

@import url("/apps/myapp/clientlib/styles/main.css");

Using Preprocessors using-preprocessors

AEM allows for pluggable preprocessors and ships with support for YUI Compressor for CSS and JavaScript and Google Closure Compiler (GCC) for JavaScript with YUI set as AEM’s default preprocessor.

The pluggable preprocessors allow for flexible usage including:

Usage usage

You can choose to configure the preprocessors configuration per clientlibrary or system-wide.

A preprocessor configuration on the clientlib node takes precedence over the OSGI configuration.

Format and Examples format-and-examples

Format format

config:= mode ":" processorName options*;
mode:= "default" | "min";
processorName := "none" | <name>;
options := ";" option;
option := name "=" value;

YUI Compressor for CSS Minification and GCC for JS yui-compressor-for-css-minification-and-gcc-for-js

cssProcessor: ["default:none", "min:yui"]
jsProcessor: ["default:none", "min:gcc;compilationLevel=advanced"]

Typescript to Preprocess and Then GCC to Minify and Obfuscate typescript-to-preprocess-and-then-gcc-to-minify-and-obfuscate

jsProcessor: [
   "default:typescript",
   "min:typescript",
   "min:gcc;obfuscate=true"
]

Additional GCC Options additional-gcc-options

failOnWarning (defaults to "false")
languageIn (defaults to "ECMASCRIPT5")
languageOut (defaults to "ECMASCRIPT5")
compilationLevel (defaults to "simple") (can be "whitespace", "simple", "advanced")

For more details on GCC options, see GCC documentation.

Set System Default Minifier set-system-default-minifier

YUI is set as the default minifier in AEM. To change this to GCC, follow these steps.