package liquibase.executor;
   
   import liquibase.database.Database;
   import liquibase.exception.UnexpectedLiquibaseException;
   import liquibase.servicelocator.ServiceLocator;
   
   import java.util.Map;
   import java.util.concurrent.ConcurrentHashMap;
   
  public class ExecutorService {
  
      private static ExecutorService instance = new ExecutorService();
  
      private Map<Database, Executor> executors = new ConcurrentHashMap<Database, Executor>();
  
      private ExecutorService() {
      }
  
      public static ExecutorService getInstance() {
          return instance;
      }
  
      public Executor getExecutor(Database database) {
          if (!executors.containsKey(database)) {
              try {
                  Executor executor = (Executor) ServiceLocator.getInstance().newInstance(Executor.class);
                  executor.setDatabase(database);
                  executors.put(database, executor);
              } catch (Exception e) {
                  throw new UnexpectedLiquibaseException(e);
              }
          }
          return executors.get(database);
      }
  
      public void setExecutor(Database database, Executor executor) {
          executors.put(database, executor);
      }
  
      public void clearExecutor(Database database) {
          executors.remove(database);
      }
  
      public void reset() {
          executors.clear();
      }
  }