docs: @Override
    public void registerXAResource(String uniqueName, XAResource xaResource) {
      Ehcache3XAResourceProducer xaResourceProducer = producers.get(uniqueName);
  
      if (xaResourceProducer == null) {
        xaResourceProducer = new Ehcache3XAResourceProducer();
        xaResourceProducer.setUniqueName(uniqueName);
        // the initial xaResource must be added before init() can be called
        xaResourceProducer.addXAResource(xaResource);
  
        Ehcache3XAResourceProducer previous = producers.putIfAbsent(uniqueName, xaResourceProducer);
        if (previous == null) {
          xaResourceProducer.init();
        } else {
          previous.addXAResource(xaResource);
        }
      } else {
        xaResourceProducer.addXAResource(xaResource);
      }
    }