code: public void setPrefix(String prefix) {
  		this.prefix = prefix;
  		if (this.prefix != null && this.prefix.isEmpty())
  			this.prefix = null;
  	}
docs: prefix prepended to the name of headers preserved.
  
  <p>Example: "{@code X-Archive-Orig-}".
  Empty String is translated to {@code null}.
  Default value is {@code null}.</p>
  @param prefix header name prefix