1.daoConfig.properties

userDaoClass=cn.itcast.jdbc.dao.impl.UserDaoJdbcImpl

#userDaoClass=cn.itcast.jdbc.dao.impl.UserDaoHibernateImpl

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public final class JdbcUtils {

 private static DataSource myDataSource = null;

 private JdbcUtils() {}

 static {

  try {

   // 注册驱动

   Class.forName("com.mysql.jdbc.Driver");// 推荐

   // DriverManager.registerDriver(new com.mysql.jdbc.Driver());//2

   // System.setProperty("jdbc.drivers","com.mysql.jdbc.Driver[:...:...]");//注册方式3可以注册多个驱动用“：”分隔。

   Properties prop = new Properties();

   // 读取配置文件

   InputStream is = JdbcUtils.class.getClassLoader().getResourceAsStream("dbcpconfig.properties");

   prop.load(is);

   myDataSource = BasicDataSourceFactory.createDataSource(prop);

  } catch (Exception e) {

   throw new ExceptionInInitializerError(e);

  }

 }

 public static Connection getConnection() throws SQLException {

  return myDataSource.getConnection();

 }

 public static void free(ResultSet rs, Statement st, Connection conn) {

  try {

   if (rs != null)

    rs.close();

  } catch (SQLException e) {

   e.printStackTrace();

  } finally {

   try {

    if (st != null)

     st.close();

   } catch (SQLException e) {

    e.printStackTrace();

   } finally {

    try {

     if (conn != null)

      conn.close();

     // myDataSource.free(conn);

    } catch (Exception e) {

     e.printStackTrace();

    }

   }

  }

 }

}

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使用单例模式：保证一个类仅有一个实例，并提供一个访问它的全局访问点。

public final class JdbcUtilsSing {

 private String url="jdbc:mysql://localhost:3306/jdbc";

 private String user="root";

 private String password="064417";

 private static JdbcUtilsSing instance=null;

// private static JdbcUtilsSing instance=new JdbcUtilsSing();

 private JdbcUtilsSing(){

  

 }

 public static JdbcUtilsSing getInstance(){

  if(instance==null){

   synchronized(JdbcUtilsSing.class){

    if(instance==null){

     instance=new JdbcUtilsSing();

    }

   }

  }

  return instance;

 }

 static{

  try {

//   注册驱动

   Class.forName("com.mysql.jdbc.Driver");//推荐

//   DriverManager.registerDriver(new com.mysql.jdbc.Driver());//2

//   System.setProperty("jdbc.drivers", "com.mysql.jdbc.Driver[:...:...]");//注册方式3可以注册多个驱动用“：”分隔。

  } catch (ClassNotFoundException e) {

   throw new ExceptionInInitializerError(e);

  }

 }

 public Connection getConnection() throws SQLException{

  return DriverManager.getConnection(url, user, password);

 }

 public void free(ResultSet rs,Statement st,Connection conn){

  try {

   if(rs!=null)

    rs.close();

  } catch (SQLException e) {

   e.printStackTrace();

  }finally{

   try {

    if(st!=null)

    st.close();

   } catch (SQLException e) {

    e.printStackTrace();

   }finally{

    try {

     if(conn!=null)

     conn.close();

    } catch (SQLException e) {

     e.printStackTrace();

    }

   }

  }

 }

}