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";

     }

 }