Java中的用户名和密码不匹配错误消息

Question

The below form , retrieves MySQL database username and password and check them with user's input.

Error messages on password or username incorrect is not showing. I tried many methods but not working as expected.

How can I code that functionality?

private void mysettingChangebtnActionPerformed(java.awt.event.ActionEvent evt) {                                                   

    String val1 = usernametxt.getText();
    String val2 = passwordtxt.getText();

    if( val1.equals("") || val2.equals("")){
           JOptionPane.showMessageDialog(null, "Fill all fields and try again .... ");
           usernametxt.setText("");
           passwordtxt.setText("");


    }

    try{

        String sql1 = "SELECT username FROM logininfo WHERE username LIKE '"+val1+"'" ;
        String sql2 = "SELECT password FROM logininfo WHERE password LIKE '"+val2+"'" ;

        pst1 = conn.prepareStatement(sql1);
        pst2 = conn.prepareStatement(sql2);


         rs1 = pst1.executeQuery();
         rs2 = pst2.executeQuery();

        while(rs1.next()){
            String uname=rs1.getString("username");
            //System.out.println(uname);

        while(rs2.next()){
           String pwd=rs2.getString("password");
            //System.out.println(pwd);



         if(val1.equals(uname) && val2.equals(pwd)){

            chg2.setVisible(true);
            this.setVisible(false);
        } else{
             JOptionPane.showMessageDialog(null, "Login Information is Incorrect. Try Again.... ");
        }

        if(!(val1.equals(uname)) || !(val2.equals(pwd))){
             JOptionPane.showMessageDialog(null, "Login Information is Incorrect. Try Again.... ");


                }
        }}




    }catch(SQLException | HeadlessException e){
        JOptionPane.showMessageDialog(null, "errrrrr"+e);

    }

}

Answer 1

you can do it using one query by passing 2 params

 "SELECT username FROM logininfo WHERE username  = '"+val1+"' 
  and password =  '"+val2+"' " ;

You need to take care of sql injection as well..Pass the parameters using preparedstatement and bind them to the query.

In your case

 while(rs1.next()){
        String uname=rs1.getString("username");
        //System.out.println(uname);
     }  // <-- close it...

      while(rs2.next()){
       String pwd=rs2.getString("password");
        //System.out.println(pwd);
    }  <--- close it..

remove the two }} at the end and try again...

Answer 2

我有这样的问题，我解决了从安全文件中删除md5加密的问题，但是也许您的数据库使用了md5加密，而您的应用程序却不尝试这样做

Answer 3

Make user that String val2 = passwordtxt.getText(); is not returning an encrypted value. Java password field might not be returning the plain text value.

Answer 4

You might need to look up the user by username AND password:

String username = usernametxt.getText();
String password = passwordtxt.getText();
// avoid SQL injection by setting query parameters with '?'
String sql = "SELECT * FROM logininfo WHERE username = ? AND password = ?";
PreparedStatement st = conn.prepareStatement(sql);
st.setString(1, username);
st.setString(2, password );
ResultSet rs = st.executeQuery();    
if (!rs.next()) {
    // no records found, login  failed
    JOptionPane.showMessageDialog(null, "Login Information is Incorrect.");
}
else {
    // record found, login succeeded
    // assuming here that there is a unique constraint in the database
    // on (username, password), otherwise multiple records could be found
    chg2.setVisible(true);
    this.setVisible(false);
}