＆＃34;当前语句的至少一个参数未初始化＆＃34;

Question

我收到了数据库错误，我无法弄清楚原因。

错误消息是：＆＃34;当前语句的至少一个参数未初始化＆＃34;

我认为这与这一行有关：

PreparedStatement stmt = cn.prepareStatement("INSERT INTO Ärende (ärendeid,kategori,budgeteradtid,status,kommentar)"
                        + "VALUES (?,?,?,?,?)");
        stmt.setString(1, getÄrendeID());
        stmt.setString(2, getKategori());
        stmt.setString(3, getbudgeteradtid());
        stmt.setString(4, getStatus());
        stmt.setString(5, getKommentar());

任何提示？

JFrame代码：

import java.awt.HeadlessException;
import java.io.IOException;
import java.sql.SQLException;
import java.util.ArrayList;
import javax.swing.DefaultListModel;
import javax.swing.JOptionPane;

/**
*
* @author lrofke
*/
public class JFrameFormTest extends javax.swing.JFrame {
DefaultListModel listModel = new DefaultListModel();

/**
 * Creates new form JFrameFormTest
 */
public JFrameFormTest() {
    initComponents();
    initÄrendeList();
}

private void initÄrendeList(){
    lstÄrende.setModel(listModel);
    //Töm lista
    listModel.clear();
    //Ladda listan med poster från db
    Ärende s = new Ärende();
    //Hämta lista med studenter
    ArrayList <Ärende> ärendeList;
    try {
        ärendeList = s.getÄrende();
        //Ladda lista med studenter
        for (Ärende st : ärendeList){
            listModel.addElement(st.toString());
        }
    } catch (SQLException ex) {
        JOptionPane.showMessageDialog(this, "FEL! " + ex.getMessage());
    }
    //Justera om "tabort"-knappen ska vara tillgänglig
    int index = listModel.getSize();
    if (index > 0){ //enable delete .
        btnDelete.setEnabled(true);
    }
}
/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jPanel1 = new javax.swing.JPanel();
    jLabel1 = new javax.swing.JLabel();
    txtKategori = new javax.swing.JTextField();
    jLabel2 = new javax.swing.JLabel();
    txtBudgeteradTid = new javax.swing.JTextField();
    jLabel3 = new javax.swing.JLabel();
    txtStatus = new javax.swing.JTextField();
    btnAdd = new javax.swing.JButton();
    jLabel4 = new javax.swing.JLabel();
    txtKommentar = new javax.swing.JTextField();
    txtÄrendeID = new javax.swing.JTextField();
    jLabel5 = new javax.swing.JLabel();
    jPanel2 = new javax.swing.JPanel();
    jScrollPane1 = new javax.swing.JScrollPane();
    lstÄrende = new javax.swing.JList();
    btnDelete = new javax.swing.JButton();
    jButton1 = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jPanel1.setBorder(javax.swing.BorderFactory.createTitledBorder("Student"));

    jLabel1.setText("Kategori:");

    txtKategori.setText("Kategori");
    txtKategori.setName(""); // NOI18N
    txtKategori.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            txtKategoriActionPerformed(evt);
        }
    });

    jLabel2.setText("Budgeterad tid:");

    txtBudgeteradTid.setText("Budgeterad tid");
    txtBudgeteradTid.setToolTipText("");
    txtBudgeteradTid.setName(""); // NOI18N
    txtBudgeteradTid.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            txtBudgeteradTidActionPerformed(evt);
        }
    });

    jLabel3.setText("Status");

    txtStatus.setHorizontalAlignment(javax.swing.JTextField.LEFT);
    txtStatus.setText("Status");
    txtStatus.setName(""); // NOI18N
    txtStatus.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            txtStatusActionPerformed(evt);
        }
    });

    btnAdd.setText("Lägg till ärende");
    btnAdd.setToolTipText("");
    btnAdd.setName(""); // NOI18N
    btnAdd.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnAddActionPerformed(evt);
        }
    });

    jLabel4.setText("Kommentar");

    txtKommentar.setText("Ange kommentar");
    txtKommentar.setToolTipText("");
    txtKommentar.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            txtKommentarActionPerformed(evt);
        }
    });

    txtÄrendeID.setText("ÄrendeID");
    txtÄrendeID.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            txtÄrendeIDActionPerformed(evt);
        }
    });

    jLabel5.setText("ÄrendeID");
    jLabel5.setToolTipText("");

    javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
    jPanel1.setLayout(jPanel1Layout);
    jPanel1Layout.setHorizontalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel1Layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                .addGroup(jPanel1Layout.createSequentialGroup()
                    .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(jLabel1)
                        .addComponent(jLabel3))
                    .addGap(14, 14, 14)
                    .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                        .addComponent(txtKategori, javax.swing.GroupLayout.DEFAULT_SIZE, 76, Short.MAX_VALUE)
                        .addComponent(txtStatus))
                    .addGap(4, 4, 4)
                    .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                            .addComponent(jLabel5, javax.swing.GroupLayout.PREFERRED_SIZE, 86, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(txtÄrendeID, javax.swing.GroupLayout.PREFERRED_SIZE, 139, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                            .addComponent(jLabel2)
                            .addGap(39, 39, 39)
                            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                .addComponent(btnAdd, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.PREFERRED_SIZE, 120, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addComponent(txtBudgeteradTid, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.PREFERRED_SIZE, 139, javax.swing.GroupLayout.PREFERRED_SIZE)))))
                .addGroup(jPanel1Layout.createSequentialGroup()
                    .addComponent(jLabel4)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addComponent(txtKommentar)))
            .addGap(519, 519, 519))
    );

    jPanel1Layout.linkSize(javax.swing.SwingConstants.HORIZONTAL, new java.awt.Component[] {btnAdd, txtBudgeteradTid});

    jPanel1Layout.setVerticalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel1Layout.createSequentialGroup()
            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel1)
                .addComponent(txtKategori, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel2)
                .addComponent(txtBudgeteradTid, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(jPanel1Layout.createSequentialGroup()
                    .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                        .addComponent(jLabel3)
                        .addComponent(txtStatus, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(txtÄrendeID, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jLabel5))
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addComponent(jLabel4)
                    .addContainerGap())
                .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                    .addGap(22, 22, 22)
                    .addComponent(txtKommentar, javax.swing.GroupLayout.DEFAULT_SIZE, 110, Short.MAX_VALUE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(btnAdd))))
    );

    txtKategori.getAccessibleContext().setAccessibleName("");

    jPanel2.setBorder(javax.swing.BorderFactory.createTitledBorder("Objektorienterad programutveckling"));

    lstÄrende.setModel(new javax.swing.AbstractListModel() {
        String[] strings = { " " };
        public int getSize() { return strings.length; }
        public Object getElementAt(int i) { return strings[i]; }
    });
    lstÄrende.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION);
    lstÄrende.setName("lstÄrende"); // NOI18N
    jScrollPane1.setViewportView(lstÄrende);

    btnDelete.setText("Ta bort");
    btnDelete.setEnabled(false);
    btnDelete.setName("btnRemove"); // NOI18N
    btnDelete.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnDeleteActionPerformed(evt);
        }
    });

    jButton1.setText("Starta webapp");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
    jPanel2.setLayout(jPanel2Layout);
    jPanel2Layout.setHorizontalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel2Layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 388, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jButton1)
                .addComponent(btnDelete))
            .addContainerGap(40, Short.MAX_VALUE))
    );
    jPanel2Layout.setVerticalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel2Layout.createSequentialGroup()
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                .addGroup(jPanel2Layout.createSequentialGroup()
                    .addComponent(btnDelete)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jButton1))
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 112, javax.swing.GroupLayout.PREFERRED_SIZE)))
    );

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, 0, Short.MAX_VALUE)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(0, 3, Short.MAX_VALUE)))
            .addContainerGap())
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(6, 6, 6))
    );

    jPanel2.getAccessibleContext().setAccessibleName("Ärendelista");

    pack();
}// </editor-fold>                        

private void btnAddActionPerformed(java.awt.event.ActionEvent evt) {                                       
    // TODO add your handling code here:
    //Skapa nytt student-objekt och 
    //läs in värdena från resp. textbox i JFrame-dialogen
    Ärende s = new Ärende();
    s.setKategori(txtKategori.getText());
    s.setbudgeteradtid(txtBudgeteradTid.getText());
    s.setstatus(txtStatus.getText());
    s.setÄrendeID(txtÄrendeID.getText());
    s.setKommentar(txtKommentar.getText());

    try {    
      //Anropa metod för att lägga till student
        if (s.addÄrende().equals("success")){
            //Ladda listan med studenter från db
            initÄrendeList();
        }else{
            JOptionPane.showMessageDialog(this, "Kunde inte lägga till student!");
        }
    } catch (SQLException | HeadlessException ex) {
        JOptionPane.showMessageDialog(this, "FEL! " + ex.getMessage());
    }

}                                      

private void txtKategoriActionPerformed(java.awt.event.ActionEvent evt) {                                            
    // TODO add your handling code here:
}                                           

private void btnDeleteActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:
    JOptionPane.showMessageDialog(this, "Funktion ej implementerad!", "Meddelande", JOptionPane.WARNING_MESSAGE);
}                                         

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    // TODO add your handling code here:
    //Öppna webbläsaren med den webbapplikation ni utvecklat
    String url = "http://localhost:8080/D0007NJSFWebAppEx/";
    try {
        java.awt.Desktop.getDesktop().browse(java.net.URI.create(url));

    } catch (IOException ex) {
        JOptionPane.showMessageDialog(this, "FEL! " + ex.getMessage());
     }  

}                                        

private void txtKommentarActionPerformed(java.awt.event.ActionEvent evt) {                                             
    // TODO add your handling code here:
}                                            

private void txtStatusActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:
}                                         

private void txtBudgeteradTidActionPerformed(java.awt.event.ActionEvent evt) {                                                 
    // TODO add your handling code here:
}                                                

private void txtÄrendeIDActionPerformed(java.awt.event.ActionEvent evt) {                                            
    // TODO add your handling code here:
}                                           

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(JFrameFormTest.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(JFrameFormTest.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(JFrameFormTest.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(JFrameFormTest.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new JFrameFormTest().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JButton btnAdd;
private javax.swing.JButton btnDelete;
private javax.swing.JButton jButton1;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JLabel jLabel5;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JList lstÄrende;
private javax.swing.JTextField txtBudgeteradTid;
private javax.swing.JTextField txtKategori;
private javax.swing.JTextField txtKommentar;
private javax.swing.JTextField txtStatus;
private javax.swing.JTextField txtÄrendeID;
// End of variables declaration                   
}

班级代码

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;

/**
*
* @author dsfsf
*/
public class Ärende {
private String kategori;
private String budgeteradtid;
private String status;
private String kommentar;
private String ärendeid;


public String getKategori() {
    return kategori;
}

public void setKategori(String kategori) {
    this.kategori = kategori;
}

public String getbudgeteradtid() {
    return budgeteradtid;
}

public void setbudgeteradtid(String budgeteradtid) {
    this.budgeteradtid = budgeteradtid;
}

public String getStatus() {
    return status;
}

public void setstatus(String status) {
    this.status = status;
}

 public String getKommentar() {
    return kommentar;
}

public void setKommentar(String kommentar) {
    this.kommentar = kommentar;



}

   public String getÄrendeID() {
    return kommentar;
}

public void setÄrendeID(String ärendeid) {
    this.ärendeid = ärendeid;



}


@Override
public String toString(){
    return this.ärendeid + "     Ärende ID     " + this.kategori + "     Kategori:     " + this.budgeteradtid + "     Budgeterad tid:     " + this.status + "     Status:     " + 
            "     Kommentar:     " + this.kommentar;

}
public String addÄrende() throws SQLException {
    //konrollera status på SQL-exekveringen
    String sRet = "failure";
    Connection cn = null;
    try{
        //Laddar db-library (derby) till applikationens minne
        Class.forName("org.apache.derby.jdbc.ClientDriver");
        //specificerar uppgifter som behövs för att koppla upp sig mot databasen
        cn = DriverManager.getConnection("jdbc:derby://localhost:1527/Fiktivt_AB;create=true;user=fiktivt;password=fiktivt");            
        //Kontrollera uppkoppling mot db
        if (cn == null){
            throw new SQLException("Uppkoppling mot databas saknas!");
        }
        //specificerar vilket SQL-uttryck som ska köras mot db
        PreparedStatement stmt = cn.prepareStatement("INSERT INTO Ärende (ärendeid,kategori,budgeteradtid,status,kommentar)"
                        + "VALUES (?,?,?,?,?)");
        stmt.setString(1, getÄrendeID());
        stmt.setString(2, getKategori());
        stmt.setString(3, getbudgeteradtid());
        stmt.setString(4, getStatus());
        stmt.setString(5, getKommentar());
        //Kör SQL-uttryck
        int i = stmt.executeUpdate();
        //Kontrollera resultat av SQL-uttryck
        if (i > 0) 
            sRet = "success";
        return sRet; //returnera status från SQL-exekvering
    }
    catch (ClassNotFoundException | SQLException ex) {
        throw new SQLException("Problem med db:" + ex.getMessage());
    }finally{
        if (cn!=null) 
            cn.close();
    }
}
public ArrayList<Ärende> getÄrende() throws SQLException{
    //Läs in information om db-uppkoppling
    Connection cn = null;
    //håller en lista med ett student-objekt för varje post i db
    ArrayList ärendeList = new ArrayList<>();
    try{
        //Laddar db-library (derby) till applikationens minne
        Class.forName("org.apache.derby.jdbc.ClientDriver");
        //specificerar uppgifter som behövs för att koppla upp sig mot databasen
        cn = DriverManager.getConnection("jdbc:derby://localhost:1527/Fiktivt_AB;create=true;user=fiktivt;password=fiktivt"); 
        //Kontrollera uppkoppling mot db
        if (cn == null){
            throw new SQLException("Uppkoppling mot databas saknas!");
        }
        PreparedStatement stmt = cn.prepareStatement("SELECT kategori,budgeteradtid,status, kommentar FROM ärende "
                        + "WHERE ärendeid = ?");

        //Kör SQL-uttryck och ladda upp posterna i ResultSet variabel rs 
        ResultSet rs = stmt.executeQuery();
        //Ladda lista med data från ResultSet (rs)
        while (rs.next()){
            //För varje post i db skapas ett student-objekt
            Ärende s = new Ärende();
            s.setKategori(rs.getString("kategori"));
            s.setbudgeteradtid(rs.getString("budgeteradtid"));
            s.setstatus(rs.getString("status"));
             s.setKommentar(rs.getString("kommentar"));
            //Lägg till student-objekt i arraylist
            ärendeList.add(s);
        }
        return ärendeList;
    }catch (ClassNotFoundException | SQLException ex) {
        throw new SQLException("Problem med db:" + ex.getMessage());
    }finally{
        if (cn!=null) 
            cn.close();
    }

}
}

Answer 1

确保get方法都没有返回null。您需要使用setNull显式设置空值。

此外，我会避免使用öäå字符，但评论和Strings除外，因为在编码更改时可能会破坏。

Answer 2

在此代码中：

    PreparedStatement stmt = cn.prepareStatement("SELECT kategori,budgeteradtid,status, kommentar FROM ärende "
                    + "WHERE ärendeid = ?");

    //Kör SQL-uttryck och ladda upp posterna i ResultSet variabel rs 
    ResultSet rs = stmt.executeQuery();

在执行查询之前，您似乎没有为WHERE子句设置参数的值。