How to check if JSF resource exists before loading view

Question

In a project using JSF, we have JavaScript files located here:

MyProject/view/javascript/*.js

In the xhtml file, I include these resources as

<script type="text/javascript" src="javascript/#{myBean.jsFileName}.js" />

This works fine, but it's possible that #{myBean.jsFileName}.js doesn't exist, in which case I want to load "Default.js".

In myBean (or in the xhtml file itself), how can I first check for the existence of a js file before setting the #{myBean.jsFileName} value? I've tried variations of this:

File f = new File("javascript/myFile.js");
if (!f.exists){ jsFileName="Default"};

But I don't think that's right. Am I on the right track?

That did it. I tried something similar before but didn't get it quite right. I was helpful to see my particular example. — Joe, Nov 26 '13 at 16:43

score 11 · Accepted Answer · edited Jun 20 '20 at 09:12

You can use ExternalContext#getResource() to obtain a web resource as URL. It will return null if resource doesn't exist. It takes a path relative to the web root and should preferably always start with /.

So. this should do in bean:

String fullPath = "/view/javascript/myFile.js";
URL resource = FacesContext.getCurrentInstance().getExternalContext().getResource(fullPath);
if (resource == null) { 
    fullPath = "/view/javascript/default.js";
}

Or, equivalently, this in the view, which is IMO somewhat hacky:

<c:set var="available" value="#{not empty facesContext.externalContext.getResource(bean.fullPath)}" />
<script src="#{available ? bean.fullPath : bean.fullDefaultPath}" />

How to check if JSF resource exists before loading view

1 Answers1

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