code: private URL getPXmlRootURL(String appName, String archiveName, Entry pxml) {
          URL pxmlUrl = pxml.getResource();
          String pxmlStr = pxmlUrl.toString();
          String pxmlRootStr = pxmlStr.substring(0, pxmlStr.length() - PERSISTENCE_XML_RESOURCE_NAME.length());
          URL pxmlRootUrl = null;
          try {
              pxmlRootUrl = new URL(pxmlRootStr);
          } catch (MalformedURLException e) {
              e.getClass(); // findbugs
              Tr.error(tc, "INCORRECT_PU_ROOT_URL_SPEC_CWWJP0025E", pxmlRootStr, appName, archiveName);
          }
          return pxmlRootUrl;
      }
docs: Determine the root of all persistence units defined in a persistence.xml. <p>
  
  This is the value that should be returned by the method getPersistenceUnitRootUrl
  on javax.persistence.spi.PersistenceUnitInfo. It is defined in the JPA 2.0
  specification as follows: <p>
  
  The jar file or directory whose META-INF directory contains the persistence.xml
  file is termed the root of the persistence unit. <p>
  
  @param appName     name of the application that contains the persistence.xml file
  @param archiveName name of the archive that contains the persistence.xml file
  @param pxml        reference to the persistence.xml file