java JDBC ArrayIndexOutOfBoundsException 时删除，更新

Question

所以我尝试创建一个 JTable，它通过 JBDC 连接到 SQL server 数据库，并具有插入、删除和编辑数据等功能。它适用于插入但更新、删除。你们能告诉我为什么我得到ArrayIndexOutOfBoundsException: -1 以及如何解决它。这是我的代码。这里的书是一个扩展JFRAME的类

public Book() {
    initComponents();

    model.addColumn("ID");
    model.addColumn("Name");
    model.addColumn("Type");

    jTable1.setModel(model);
    displayTable();
    jTable1.getSelectionModel().addListSelectionListener(new ListSelectionListener() {
        @Override
        public void valueChanged(ListSelectionEvent e) {
            int row = jTable1.getSelectedRow();

            txtName.setText(jTable1.getValueAt(row, 1).toString());
            txtType.setText(jTable1.getValueAt(row, 2).toString());

        }
    });

}

public void displayTable() {
    try {
        model.setRowCount(0);
        ConnectToSQL sql = new ConnectToSQL();
        connection = sql.getConnection();
        st = connection.createStatement();
        ResultSet result = st.executeQuery("SELECT * FROM BOOK");
        while (result.next()) {
            model.addRow(new Object[]{result.getInt("id"), result.getString("name"), result.getString("type")});
        }

    } catch (SQLException ex) {
        Logger.getLogger(Book.class.getName()).log(Level.SEVERE, null, ex);
    }
}

private void btnUpdateActionPerformed(java.awt.event.ActionEvent evt) {
    // TODO add your handling code here:
    int row = jTable1.getSelectedRow();
    String id = jTable1.getValueAt(row, 0).toString();
    try {
        // TODO add your handling code here:
        st.executeUpdate("Update Book set name ='" + txtName.getText() + "',type='" + txtType.getText() + "' where id =" + id);
        displayTable();

    } catch (SQLException ex) {
        Logger.getLogger(Book.class.getName()).log(Level.SEVERE, null, ex);
    }

}

private void btnDeleteActionPerformed(java.awt.event.ActionEvent evt) {
    // TODO add your handling code here:
    int row = jTable1.getSelectedRow();
    String id = jTable1.getValueAt(row, 0).toString();
    try {
        // TODO add your handling code here:
        st.executeUpdate("Delete from book where id =" + id);
        displayTable();

    } catch (SQLException ex) {
        Logger.getLogger(Book.class.getName()).log(Level.SEVERE, null, ex);
    }

}

Answer 1

你得到这个错误，因为你没有选择任何行，所以为了避免这个问题你必须使用：

if(jTable1.getSelectedRow() != -1){
   int row = jTable1.getSelectedRow();
   String id = jTable1.getValueAt(row, 0).toString();
   //rest of your code here
}else{
   //show an error for example, no row is selected
}

---

注意

而不是：

st.executeUpdate("Update Book set name ='" + txtName.getText() + "',type='" + txtType.getText() + "' where id =" + id);

你必须使用 PreparedStatement 来避免任何语法错误或 SQL 注入

例如：

String query = "Update Book set name = ?, type=? where id =?";

try (PreparedStatement update = connection.prepareStatement(query)) {

    update.setString(1, txtName.getText());
    update.setString(2, txtType.getText());
    update.setInt(3, id);

    update.executeUpdate();
}

另外，你的 id 是 int，所以你不能像你必须设置一个 int 那样为你的查询设置一个字符串：

String id = jTable1.getValueAt(row, 0).toString();

相反，您必须使用：

int id = Integer.parseInt(jTable1.getValueAt(row, 0).toString());