Java 更改用户JDBC连接

我正在尝试更改连接到我的数据库的用户，但它不起作用，我只能使用第一个。我该怎么做

public class Model {
    private String user;
    private String passwd;
    private String url;
    private String matricule;
    private static Model model;
    private Connection connect; 
    private DoctorsModel doctorsModel;
    private ConnexionModel connexionModel;
    private MedicineModel medicineModel;
    private VisitorsModel visitorsModel;
    private ReportModel reportModel;
    private NewReportModel newReportModel;

    private Model(String user, String passwd){
        this.user = user;
        this.passwd = passwd;
        url="myurl";

        try {
            Class.forName("com.mysql.jdbc.Driver");
            System.out.println("Driver OK");

            this.connect = DriverManager.getConnection(url, user, passwd);
            this.connexionModel = new ConnexionModel(connect,url,user,passwd);
            this.doctorsModel = new DoctorsModel(connect);
            this.medicineModel = new MedicineModel(connect);
            this.visitorsModel = new VisitorsModel(connect);
            this.reportModel = new ReportModel(connect);
            this.newReportModel = new NewReportModel(connect,matricule);
        }

        catch (Exception e){
            Alert error = new Alert(Alert.AlertType.WARNING);
            error.setTitle("Erreur");
            error.setHeaderText(null);
            error.setContentText("Une erreur a été rencontrée, veuillez réessayer plus tard.");
            error.showAndWait();
            System.exit(0);
            e.printStackTrace();
        }
    }
    public static Model getInstance()
    {
        if (model==null)
        {
            model = new Model("firstuser","passwd");
        }
        return model;
    }

    public ConnexionModel getConnexionModel()
    {
        return connexionModel;
    }

    public DoctorsModel getDoctorsModel()
    {
        return doctorsModel;
    }

    public MedicineModel getMedicineModel()
    {
        return medicineModel;
    }

    public VisitorsModel getVisitorsModel()
    {
        return visitorsModel;
    }

    public ReportModel getReportModel()
    {
        return reportModel;
    }

    public NewReportModel getNewReportModel()
    {
        return newReportModel;
    }

    public void setUser(String user)
    {
        this.user = user;
    }

    public void setPasswd(String passwd)
    {
        this.passwd = passwd;
    }
    public void setConnection()
    {
        try
        {
            connect = DriverManager.getConnection(url,user,passwd);
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }
    public void getConnection()
    {
        System.out.println(connect);
    }

    public void setMatricule(String matricule)
    {
        this.matricule = matricule;
    }

    public String getMatricule(String matricule)
    {
        return matricule;
    }}

---

我在我的

ConnectionController

上调用

setConnection（）

，没什么特别的，我在前后打印了

连接，打印了用户、密码，一切都正确更改了。。。在再次设置之前，我尝试关闭连接，但它只是告诉我连接已关闭，我无法再进行任何访问。
您是否检查了异常消息？请将其附在您保留模型对象中第一个连接的引用的问题上
this.doctorsModel=new doctorsModel（connect）。。。好吧，我很笨。除息的