package liquibase.precondition.core;
   
   import liquibase.changelog.ChangeSet;
   import liquibase.changelog.DatabaseChangeLog;
   import liquibase.database.Database;
   import liquibase.exception.PreconditionErrorException;
   import liquibase.exception.PreconditionFailedException;
   import liquibase.exception.ValidationErrors;
   import liquibase.exception.Warnings;
  import liquibase.precondition.Precondition;
  import liquibase.snapshot.DatabaseSnapshotGeneratorFactory;
  import liquibase.util.StringUtils;
  
  public class ViewExistsPrecondition implements Precondition {
      private String schemaName;
      private String viewName;
  
      public String getSchemaName() {
          return schemaName;
      }
  
      public void setSchemaName(String schemaName) {
          this.schemaName = StringUtils.trimToNull(schemaName);
      }
  
      public String getViewName() {
          return viewName;
      }
  
      public void setViewName(String viewName) {
          this.viewName = viewName;
      }
  
      @Override
      public Warnings warn(Database database) {
          return new Warnings();
      }
  
      @Override
      public ValidationErrors validate(Database database) {
          return new ValidationErrors();
      }
  
      @Override
      public void check(Database database, DatabaseChangeLog changeLog, ChangeSet changeSet)
              throws PreconditionFailedException, PreconditionErrorException {
          try {
              if (!DatabaseSnapshotGeneratorFactory.getInstance().getGenerator(database)
                      .hasView(getSchemaName(), getViewName(), database)) {
                  throw new PreconditionFailedException("View "
                          + database.escapeTableName(getSchemaName(), getViewName()) + " does not exist", changeLog, this);
              }
          } catch (PreconditionFailedException e) {
              throw e;
          } catch (Exception e) {
              throw new PreconditionErrorException(e, changeLog, this);
          }
      }
  
      @Override
      public String getName() {
          return "viewExists";
      }
  }