It is often helpful to have diagnostic information about the pages in our web application for analyzing and resolving issues. Aside from the usual error reporting mechanism of our web container, the JSF framework lacks a reliable means of obtaining detailed and precise error information about the pages in our JSF application.
Fortunately, the Facelets framework provides comprehensive diagnostic information to simplify debugging our JSF pages. For example, Facelets can provide detailed information about invalid EL expressions in our views. First, we must set the
facelets.DEVELOPMENT initialization parameter to true in
web.xml to enable detailed error reporting.
The following Facelets page example contains an unbalanced ...