code: public void setFromJson(final byte[] persisted) {
      try {
        SessionState decoded = JACKSON.readValue(persisted, SessionState.class);
        decoded.foreachPartition(new Action1<PartitionState>() {
          int i = 0;
  
          @Override
          public void call(PartitionState dps) {
            partitionStates.set(i++, dps);
          }
        });
      } catch (Exception ex) {
        throw new RuntimeException("Could not decode SessionState from JSON.", ex);
      }
    }
docs: Recovers the session state from persisted JSON.
  
  @param persisted the persisted JSON format.