code: public String getMainAttribute(String attributeName, String defaultValue) {
  		Attributes attributes = this.manifest.getMainAttributes();
  		String attributeValue = (attributes != null ? attributes.getValue(attributeName) : null);
  
  		return (attributeValue != null ? attributeValue : defaultValue);
  	}
docs: Gets a manifest's main attribute.
  
  @param attributeName the attribute name to get.
  @param defaultValue the default value to return in case the attribute undefined.
  @return the found attribute value or the submitted default value in case the attribute is undefined.