package main.java.com.qianfeng.review; import java.io.IOException; import java.sql.*; import java.util.*; public class JDBCUtils {
      private static Properties properties;     private static String url;     private static String driverClass;     private static String username;     private static String password;     private static Connection connection = null;     private static PreparedStatement pstmt ;     static {
          properties = new Properties();         try {
              // properties.load(new FileInputStream(new File("db.properties")));             properties.load(JDBCUtils.class.getResourceAsStream("db.properties"));             url = properties.getProperty("url");             driverClass = properties.getProperty("driverClass");             username = properties.getProperty("username");             password = properties.getProperty("password");         } catch (IOException e) {
              e.printStackTrace();         }     }     //得到连接     public static Connection getConnection(){
          try {
              Class.forName(driverClass);             connection = DriverManager.getConnection(url,username,password);         } catch (ClassNotFoundException e) {
              e.printStackTrace();         } catch (SQLException e) {
              e.printStackTrace();         }         return connection;     }     //关闭所有连接     public static void closeAll(Connection conn, Statement statement, ResultSet resultSet){
              try {
                  if (resultSet!=null){
                  resultSet.close();                 }                 if (conn!=null){
                      conn.close();                 }                 if (statement!=null){
                      statement.close();                 }             } catch (SQLException e) {
                  e.printStackTrace();             }     }     //增加，删除，修改     public static boolean updateByPreparedStatement(String sql, List