I've done tutorial about Facelets templating.
Now I've tried to create a page that isn't in same directory as the template. I've got problems with page style, because of styles are referenced with relative path like so:
<link rel="stylesheet" href="style_resource_path.css" />
I can use absolute referencing by starting with /:
<link rel="stylesheet" href="/project_root_path/style_resource_path.css" />
But this will bring me troubles when I'll be moving application to a different context.
So I'm wondering what is best way to reference CSS (and JS and image) resources in Facelets?
The proper way is using <h:outputStylesheet>, <h:outputScript> and <h:graphicImage> with a name referring the path relative to webapp's /resources folder. This way you don't need to worry about the context path.
Drop the CSS/JS/image files in /resources folder of the public webcontent as below (just create one if not already exist at the same level as /WEB-INF and /META-INF).
src
`-- main
|-- java
|-- resources
`-- webapp
|-- resources
| |-- css
| | |-- other.css
| | `-- style.css
| |-- images
| | |-- background.png
| | |-- favicon.ico
| | `-- logo.png
| `-- js
| `-- script.js
|-- META-INF
| `-- MANIFEST.MF
|-- WEB-INF
| |-- faces-config.xml
| `-- web.xml
`-- page.xhtml
Do note that it's in /main/webapp/resources and thus not /main/resources. The /main/resources is for Java resources (properties/xml/text/config files) which must end up in runtime classpath. The /main/webapp/resources is for Web resources. See also Maven and JSF webapp structure, where exactly to put JSF resources.
Ultimately, those resources are available as below everywhere without the need to fiddle with relative paths:
<h:head>
...
<h:outputStylesheet name="css/style.css" />
<h:outputScript name="js/script.js" />
</h:head>
<h:body>
...
<h:graphicImage name="images/logo.png" />
...
</h:body>
The name attribute must represent the full path relative to the /resources folder. It does not need to start with /. You do not need the library attribute as long as you aren't developing a component library like PrimeFaces or a common module JAR file which is shared by multiple webapps.
You can reference the <h:outputStylesheet> anywhere, also in <ui:define> of template clients without the need for an additional <h:head>. It will via the <h:head> component of master template automatically end up in generated <head>.
<ui:define name="...">
<h:outputStylesheet name="css/style.css" />
...
</ui:define>
You can reference <h:outputScript> also anywhere, but it will by default end up in the HTML exactly there where you declared it. If you want it to end up in <head> via <h:head>, then add target="head" attribute.
<ui:define name="...">
<h:outputScript name="js/script.js" target="head" />
...
</ui:define>
Or, if you want it to end up at the end of <body> (right before </body>, so that e.g. window.onload and $(document).ready() etc isn't necessary) via <h:body>, then add target="body" attribute.
<ui:define name="...">
<h:outputScript name="js/script.js" target="body" />
...
</ui:define>
HeadRendererIn case you're using PrimeFaces, it's important to know that it unfortunately comes along with a custom renderer for <h:head>. It will messup the standard JSF <h:head> ordering of scripts as described above. You're basically forced to force the order via PrimeFaces-specific <f:facet name="first|middle|last">, which may end up in untemplateable code (you cannot anymore safely add scripts at expected locations from your own custom components/composites). You may want to turn off the PrimeFaces HeadRenderer as described in this answer.
The proper way to add component library specific themes/scripts is using a SystemEventListener on PostAddtoViewEvent of <h:head>, not using a custom HeadRenderer. See also How to load a JavaScript file on all pages programmatically
You can even package the resources in a JAR file. See also Structure for multiple JSF projects with shared code.
You can in EL use the #{resource} mapping to let JSF basically print a resource URL like /context/jakarta.faces.resource/folder/file.ext.xhtml?ln=library so that you could use it as e.g. CSS background image or favicon. The only requirement is that the CSS file itself should also be served as a JSF resource, otherwise EL expressions won't evaluate. See also How to reference JSF image resource as CSS background image url.
.some {
background-image: url("#{resource['images/background.png']}");
}
Here's the @import example.
@import url("#{resource['css/other.css']}");
Here's the favicon example. See also Add favicon to JSF project and reference it in <link>.
<link rel="shortcut icon" href="#{resource['images/favicon.ico']}" />
In case you're using a SCSS compiler such as Dart, then keep in mind that the SCSS processor might interpret # as a special character. In that case you would need to escape it with \.
.some {
background-image: url("\#{resource['images/background.png']}");
}
Third party CSS files loaded via <h:outputStylesheet> which in turn reference fonts and/or images may need to be altered to use #{resource} expressions as described in previous section, otherwise an UnmappedResourceHandler needs to be installed in order to be able to serve those using JSF. See also a.o. Bootsfaces page shows up in browser without any styling and How to use 3rd party CSS libraries such as Font Awesome with JSF? Browser can't find font files referenced in the CSS file.
Better yet is to investigate if these third party CSS files aren't already available as so-called "web jars", this way you can simply include them as a Maven dependency instead of copying the physical files into the project. Start at webjars.org site and/or org.webjars Maven group. It covers jQuery, Bootstrap, Font Awesome and many more. For example Font Awesome can simply be installed as follows:
<dependency>
<groupId>org.webjars</groupId>
<artifactId>font-awesome</artifactId>
<version>6.5.1</version>
</dependency>
And be referenced as follows:
<h:outputStylesheet library="webjars" name="font-awesome/6.5.1/css/all.min-jsf.css" />
The associated fonts/images are already correctly referenced.
If you intend to hide the resources from public access by moving the whole /resources folder into /WEB-INF, then you can since JSF 2.2 optionally change the webcontent-relative path via a new web.xml context parameter as follows:
<context-param>
<param-name>jakarta.faces.WEBAPP_RESOURCES_DIRECTORY</param-name>
<param-value>/WEB-INF/resources</param-value>
</context-param>
In older JSF versions this is not possible.