java.sql.SQLException : Access denied for user 'root' @'localhost' (using password: YES) 异常

Question

为什么你认为这个函数给我的总是空值？？使用另一个具有相同代码结构的登录程序，效果非常好。我的 DBURL 是 jdbc:mysql://localhost:8889/database

    public String retrieveUserPassword(String userName, String password) {

    String query = "SELECT UserPassword FROM Access where UserName='"+userName+"'";
    String dbresult=null; //this might be the problem, but I must define it

    try {
      Class.forName("com.mysql.jdbc.Driver");

    }catch (ClassNotFoundException ex1) {

      System.out.println("Driver could not be loaded: " + ex1);
      Logger.getLogger(DatabaseModel.class.getName()).log(Level.SEVERE, null, ex1);
    }
    try {

          //These are private variables declared at the top of the class 
          //and used by various functions   
          con = DriverManager.getConnection(DatabaseURL, userName, password);   
          st = con.createStatement(); 
          rs = st.executeQuery(query);

            if(rs.next()){

                dbresult= rs.getString(3);
            }

     }catch (SQLException e) {

      e.printStackTrace();
     }    

  return dbresult;

}

Access表由三列组成:用户 ID、用户名、用户密码

Answer 1

java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES)

正如您所提到的，问题在于与数据库本身建立连接。声明

con = DriverManager.getConnection(DatabaseURL, userName, password);

正在抛出被捕获的异常

catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }   

之后，您将返回已初始化为 null 的 dbresult(您必须这样做，因为它是一个局部变量)。所以问题是由于身份验证，您无法连接到您的数据库。

在你的机器上(在你的情况下是本地主机)从控制台运行以下命令

GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' IDENTIFIED BY 'root' WITH GRANT OPTION;