Hello, I have this very strange error with h:graphicImage

This code works fine :-

<h:graphicImage value="/Common/Images/#{item.templatePicName}"/>

And this one doesn't :-

<h:graphicImage alt="${app:getCommonImagePath(item.templatePicName)}"  value="${app:getCommonImagePath(item.templatePicName)}" />

It only shows alt value /Common/Images/Sunset.jpg which is perfectly fine and works in 1st case. Then why doesn't it work in 2nd case? There are no problems with my images. They are present in right directory.

here getCommonImagePath is my custom EL function, whose definition is :

package Common;


public final class AppDeployment {

    private AppDeployment(){ //hide constructor

    }

    private static String commonImageFolderPath = "/Common/Images/";
    public static String getCommonImagePath(String picName){
        return commonImageFolderPath + picName;
    }
}