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/*
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  DBPool : Java Database Connection Pooling 
  Copyright (c) 2001-2013 Giles Winstanley. All Rights Reserved.

  This is file is part of the DBPool project, which is licensed under
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  4. Redistributions of modified versions of the source code, must be
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  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER "AS IS" AND ANY EXPRESS OR
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 */
package snaq.db;

import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * {@link ConnectionValidator} implementation that validates database
 * connections by issuing a SQL query, and simply checking if the query
 * succeeded or failed.
 * By default it does not check if any results are returned.
 * This class is provided as a convenience for providing
 * connection validation.
 *
 * @author Giles Winstanley
 */
public class SimpleQueryValidator extends QueryValidator
{
  /** SQL query string to be issued to the database for connection validation. */
  private String query = null;
  /** Flag determining whether to check for returned results. */
  private boolean checkHasResults = false;

  /**
   * Creates a new {@code SimpleQueryValidator} instance using the
   * specified SQL query string. The created instance will not check for
   * existence of returned results, only that the query succeeded.
   * @param query SQL query to issue for validation
   */
  public SimpleQueryValidator(final String query)
  {
    this.query = query;
  }

  /**
   * Creates a new {@code SimpleQueryValidator} instance using the
   * specified SQL query string.
   * @param query SQL query to issue for validation
   * @param checkHasResults whether to check if any results are returned
   */
  public SimpleQueryValidator(String query, boolean checkHasResults)
  {
    this.query = query;
    this.checkHasResults = checkHasResults;
  }

  /**
   * Returns the SQL query string to be issued to the database.
   * @return query string in SQL syntax
   */
  @Override
  public String getQueryString()
  {
    return query;
  }

  /**
   * Checks the results of the SQL query to see if it indicates a valid connection.
   * This implementation simply comprises:
   *    *     return checkHasResults ? results.next() : true;
   * 
   * such that if results-checking was specified when the instance was created
   * then the connection is only validated if some results are returned,
   * otherwise the simply fact of the statement being executed successfully
   * is used for validation.
   * @param results {@code ResultSet} instance produced from SQL query
   * @return boolean indicating whether checked results indicated a valid connection
   * @throws SQLException if checking the results throws such an exception
   */
  @Override
  public boolean checkResults(ResultSet results) throws SQLException
  {
    return checkHasResults ? results.next() : true;
  }
}