code: @Override
      public void setIsolationLevel(IsolationLevel level) throws IllegalStateException {
          if(level != IsolationLevels.SNAPSHOT){
              throw new IllegalStateException("Only IsolationLevels.SNAPSHOT level supported.");
          }else{
              super.setIsolationLevel(level);
          }
      }
docs: sets transaction isolationlevel (only IsolationLevels.SNAPSHOT supported)
  
  @param level
  @throws IllegalStateException