登錄表單錯誤+ JDBC CONNECTIVITY（JAVA-MYSQL）

Question

我有一個具有JDBC連接（JAVA-MYSQL）的項目，該項目具有登錄表單。 但是編碼不起作用。（這意味着它始終顯示“ WRONG PASSWORD”（錯誤密碼），盡管我確定它是正確的）。

請找到錯誤。 （因為它沒有顯示）。

 private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { String S; String email = jTextField3.getText(); try { Class.forName("java.sql.Driver"); Connection con = DriverManager.getConnection("jdbc:Mysql://localhost/nami", "root", "123456"); Statement st = con.createStatement(); S = "SELECT password FROM signup WHERE email =" + "'" + email + "'" + ";"; st.executeQuery(S); String pass = new String(jPasswordField2.getPassword()); if (pass.equals("S")) { jOptionPane1.showMessageDialog(null, "YOU HAVE SUCCESSFULLY LOGGED IN"); MAINPAGE at = new MAINPAGE(); jDesktopPane1.add(at); at.show(); } else { jOptionPane1.showMessageDialog(null, "WRONG PASSWORD!!"); } } catch (Exception e) { jOptionPane2.showMessageDialog(null, "Error" + e.getMessage()); } } 

Answer 1

pass.equals("S")表示您的密碼應始終為S才能成功登錄。

您需要從數據庫中查詢，然后進行比較。

Result rs = st.executeQuery(S);
String queryPass = null;
if(rs.next()){
   queryPass = rs.getString("password");
}

if (pass.equals(queryPass)) {
  jOptionPane1.showMessageDialog(null, "YOU HAVE SUCCESSFULLY LOGGED IN");
  MAINPAGE at = new MAINPAGE();
  jDesktopPane1.add(at);
  at.show();

} else {
  jOptionPane1.showMessageDialog(null, "WRONG PASSWORD!!");
}

順便說一句，將參數直接傳遞到sql中是一個壞主意，您需要使用PreparedStatement而不是Statement來避免SQL注入

Answer 2

＃＃ 嘗試這個 ＃＃

 String email=request.getParameter("email");
   String pass=request.getParameter("pass");



                     Class.forName("com.mysql.jdbc.Driver");
                     Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/users_record","root","root");
                     Statement st1=con.createStatement();
                     ResultSet obj1=st1.executeQuery("select * from registration where email='" +email+ "'");

                     System.out.println(email);        
                     while(obj1.next())
                        {

                             String p2=obj1.getString(5);
                             if(p2.equals(pass))
                                 {

                                     response.sendRedirect("home1.jsp?msg=YOU HAVE SUCCESSFULLY LOGGED IN ");


                                 }
                             else
                                 {
                                       response.sendRedirect("login1.jsp?msg=Invalid password");
                                 }
                        }