Ajax实现下拉框三级联动

package util; import java.sql.*; public final class DatabaseConnection { public static Connection getConnection(String driver, String url, String user, String pwd) { Connection connection = null; try { Class.forName(driver); connection = DriverManager.getConnection(url, user, pwd); } catch (Exception e) { e.printStackTrace(); } return connection; } public static Connection getConnection() { String strDriver = "com.microsoft.sqlserver.jdbc.SQLServerDriver"; String strUrl = "jdbc:sqlserver://127.0.0.1:1433;databaseName=teacherdb"; String strUser = "sa"; String strPwd = ""; return getConnection(strDriver, strUrl, strUser, strPwd); } public static void close(Connection connection) { try { if (connection != null) { connection.close(); } } catch (SQLException sqle) { sqle.printStackTrace(); } } public static void close(Connection connection, Statement statement) { try { if (statement != null) { statement.close(); } if (connection != null) { connection.close(); } } catch (SQLException sqle) { sqle.printStackTrace(); } } public static void close(Connection connection, Statement statement, ResultSet resultSet) { try { if (resultSet != null) { resultSet.close(); } if (statement != null) { statement.close(); } if (connection != null) { connection.close(); } } catch (SQLException sqle) { sqle.printStackTrace(); } } public static void close(Connection connection, PreparedStatement preparedStatement) { try { if (preparedStatement != null) { preparedStatement.close(); } if (connection != null) { connection.close(); } } catch (SQLException sqle) { sqle.printStackTrace(); } } public static void close(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet) { try { if (resultSet != null) { resultSet.close(); } if (preparedStatement != null) { preparedStatement.close(); } if (connection != null) { connection.close(); } } catch (SQLException sqle) { sqle.printStackTrace(); } } }