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 am trying to use JsfUnit to create automated tests. I can get ahold of the UICompoment objects from within the test methods. However, I couldn't find a way to check the Html generated by the component.

Rinna

Do you want to analyze it manually? If so then just inspect the html from your browser using for example Firebug; If not, then - what are you really trying to do? – Orling

@dratewka, I have improved my question so you can understand what I am trying to achieve. – Rinna

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();
// ...

Sinistrodextral

perfect BalusC! I have used this code on the test environment and it works! Thanks a lot. – Rinna

great answer, as usual, thanks. Could you please elaborate on "when sitting in render response phase, this needs to be done differently"? – Umiak

Answer 2

Solution by BalusC to invoke UIComponent#encodeAll()generally works, but I had a problem with unicode characters when using utf-8 encoding. All non-ascii characters in ajax response were damaged after I modified current context's response writer.

Instead of modifying response writer on current context retrieved by FacesContext.getCurrentInstance(), I created a wrapper over current context by extending FacesContextWrapper, so that original context is left unmodified:

StringWriter writer = new StringWriter();
FacesContext context = new FacesContextWrapper() {
    private ResponseWriter internalWriter = getWrapped()
        .getRenderKit().createResponseWriter(writer, "text/html", "UTF-8");

    @Override
    public FacesContext getWrapped() {
        return FacesContext.getCurrentInstance();
    }

    @Override
    public ResponseWriter getResponseWriter() {
        return internalWriter;
    }

};

component.encodeAll(context);
String output = writer.toString();

Urba