private boolean evalBooleanExpression(String param, boolean defaultValueIfNull) {
        String paramValue = context.getExternalContext().getInitParameter(param);
        if (paramValue == null) {
            return defaultValueIfNull;
        }
        else {
            ELContext elContext = context.getELContext();
            ExpressionFactory expressionFactory = context.getApplication().getExpressionFactory();
            ValueExpression expression = expressionFactory.createValueExpression(elContext, paramValue, String.class);
            String expressionValue = expression.getValue(elContext);
            return expressionValue == null || Boolean.parseBoolean(expressionValue);
        }
    }
Overrides eventually set ignoreAutoUpdate from client.
May be used e.g. combined with server-side update via <code>PrimeFaces.current().ajax().update("xxx")</code>
@param ignoreAutoUpdate
primefaces/src/main/java/org/primefaces/context/PrimeRequestContext.java