Is there a way to get the generated HTML as a String from a UIComponent object?

Question

I have a UIComponent object. I would like to get the HTML code generated by this component at runtime so I can analyze it.

Is there a way to achieve this?

I

Answer 1

Just do the same what JSF does under the covers: invoke UIComponent#encodeAll(). To capture the output, set the response writer to a local buffer by FacesContext#setResponseWriter().

E.g. (assuming that you're sitting in invoke application phase; when sitting in render response phase, this needs to be done differently):

FacesContext context = FacesContext.getCurrentInstance();
ResponseWriter originalWriter = context.getResponseWriter();
StringWriter writer = new StringWriter();

try {
    context.setResponseWriter(context.getRenderKit().createResponseWriter(writer, "text/html", "UTF-8"));
    component.encodeAll(context);
} finally {
    if (originalWriter != null) {
        context.setResponseWriter(originalWriter);
    }
}

String output = writer.toString();
// ...