Java 如何在JFrame上刷新数据库查询？

你好

我在向JTable框架显示数据库的更新版本时遇到问题

JFrame中的所有内容都是刚刚生成的，我只需按照此链接中的说明进行操作：

它可以正常工作，直到我为数据库的更新添加了一个新的JFrame，当我点击按钮查看库存时（JFrame由显示MySQL数据的JTable组成），它不会显示数据库的更新版本

但是，在关闭应用程序并运行ViewInventory JFrame之后。。它已经更新了

请帮忙。。。这是生成的代码：

public class ViewInventory extends javax.swing.JFrame {

    public ViewInventory() {
        initComponents();
        setLocation(300, 120);
    }
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {
        bindingGroup = new org.jdesktop.beansbinding.BindingGroup();

        inventoryPUEntityManager = java.beans.Beans.isDesignTime() ? null : javax.persistence.Persistence.createEntityManagerFactory("inventoryPU").createEntityManager();
        itemsQuery = java.beans.Beans.isDesignTime() ? null : inventoryPUEntityManager.createQuery("SELECT i FROM Items i");
        itemsList = java.beans.Beans.isDesignTime() ? java.util.Collections.emptyList() : itemsQuery.getResultList();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();
        jLabel1 = new javax.swing.JLabel();
        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jTable1.setAutoCreateRowSorter(true);
        jTable1.setAlignmentX(1.0F);
        jTable1.setAlignmentY(2.0F);
        jTable1.setAutoResizeMode(javax.swing.JTable.AUTO_RESIZE_ALL_COLUMNS);
        jTable1.setSelectionMode(javax.swing.ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);

        org.jdesktop.swingbinding.JTableBinding jTableBinding = org.jdesktop.swingbinding.SwingBindings.createJTableBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ_WRITE, itemsList, jTable1);
        org.jdesktop.swingbinding.JTableBinding.ColumnBinding columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${id}"));
        columnBinding.setColumnName("Id");
        columnBinding.setColumnClass(Integer.class);
        columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${itemName}"));
        columnBinding.setColumnName("Item Name");
        columnBinding.setColumnClass(String.class);
        columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${category}"));
        columnBinding.setColumnName("Category");
        columnBinding.setColumnClass(String.class);
        columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${QBox}"));
        columnBinding.setColumnName("QBox");
        columnBinding.setColumnClass(Integer.class);
        columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${unitPriceBox}"));
        columnBinding.setColumnName("Unit Price Box");
        columnBinding.setColumnClass(Double.class);
        columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${subTotalBox}"));
        columnBinding.setColumnName("Sub Total Box");
        columnBinding.setColumnClass(Double.class);
        columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${QPc}"));
        columnBinding.setColumnName("QPc");
        columnBinding.setColumnClass(Integer.class);
        columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${unitPricePc}"));
        columnBinding.setColumnName("Unit Price Pc");
        columnBinding.setColumnClass(Double.class);
        columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${subTotalPc}"));
        columnBinding.setColumnName("Sub Total Pc");
        columnBinding.setColumnClass(Double.class);
        columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${grandTotal}"));
        columnBinding.setColumnName("Grand Total");
        columnBinding.setColumnClass(Double.class);
        bindingGroup.addBinding(jTableBinding);

        jScrollPane1.setViewportView(jTable1);

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

        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(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 514, Short.MAX_VALUE)
                    .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 329, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jButton1, javax.swing.GroupLayout.Alignment.TRAILING))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 275, Short.MAX_VALUE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 14, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(14, 14, 14)
                .addComponent(jButton1)
                .addContainerGap())
        );

        bindingGroup.bind();

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

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        new Menu().setVisible(true);
        setVisible(false);
    }                                        

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new ViewInventory().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.persistence.EntityManager inventoryPUEntityManager;
    private java.util.List<inventory.Items> itemsList;
    private javax.persistence.Query itemsQuery;
    private javax.swing.JButton jButton1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable jTable1;
    private org.jdesktop.beansbinding.BindingGroup bindingGroup;
    // End of variables declaration                   
}

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我个人不喜欢Netbeans gui设计器有很多原因。这对于原型设计和小项目来说非常好，对于大项目和回去做维护来说非常糟糕。但这是另一次的咆哮

问题是，您从JPA查询返回了一个静态列表。您需要让GUI在编辑事件之后重新运行查询以获得更新的列表。我在gui设计器中实现这类功能的方法是在“自定义创建代码”中将集合更改为可观察列表：

---

我这样做是因为我是通过EJB远程会话bean获取列表的，很久以前我在netbeans 6.5或7（上次我使用GUI设计器创建新表单）中就这样做了。显然，现在有一个“可修改包装器””和“可观察的””可以对查询结果进行设置。这可能会满足您的需要，否则按上述手动方式进行。

我编辑了您的帖子，如果不是，请还原…，只需一个通知-对于DB语句，您必须添加finally块，在该块中，您还必须关闭连接和ResultSet

try {
            Class.forName(Connect.DRIVER);
            Connection con = DriverManager.getConnection(Connect.CONNECTION_STRING,
                    Connect.USERNAME, Connect.PASSWORD);

            Statement stat = con.createStatement();

            ResultSet rs = stat.executeQuery("SELECT id, category,"
                    + "q_box, unit_price_box, sub_total_box, q_pc, "
                    + "unit_price_pc, sub_total_pc, grand_total from items WHERE "
                    + "item_name = '" + item_name_combobox.getSelectedItem() + "';");

            String category;
            int q_box, q_pc;
            double unit_price_box, sub_total_box, unit_price_pc, sub_total_pc,
                    grand_total;

            if (rs.next()) {
                q_box = rs.getInt("q_box");
                category = rs.getString("category");
                unit_price_box = rs.getDouble("unit_price_box");
                sub_total_box = rs.getDouble("sub_total_box");
                q_pc = rs.getInt("q_pc");
                unit_price_pc = rs.getDouble("unit_price_pc");
                sub_total_pc = rs.getDouble("sub_total_pc");
                grand_total = rs.getDouble("grand_total");

                double new_sub_total_box = q_box * Integer.parseInt(new_unit_price_box_txtfld.getText());
                double new_sub_total_pc = q_pc * Integer.parseInt(new_unit_price_pc_txtfld.getText());
                grand_total = new_sub_total_box + new_sub_total_pc;

            stat.executeUpdate("UPDATE items SET unit_price_box = " + new_unit_price_box_txtfld.getText()
                    + ", unit_price_pc = " + new_unit_price_pc_txtfld.getText()
                    + ", sub_total_box = " + new_sub_total_box
                    + ", sub_total_pc = "+ new_sub_total_pc
                    + ", grand_total = "+ grand_total
                    + " WHERE item_name = '"
                    + item_name_combobox.getSelectedItem() + "';");

                sub_total_box_txtfld.setText(Double.toString(new_sub_total_box));
                sub_total_pc_txtfld.setText(Double.toString(new_sub_total_pc));
                grand_total_txtfld.setText(Double.toString(grand_total));

                lblmsg.setText("Record Saved!");

                con.close();
            }
        } catch (Exception e) {
            lblmsg.setText("Error: "+ e.getMessage());
            System.out.println("Error: "+ e.getMessage());
        }

someList = Beans.isDesignTime() ? java.util.Collections.emptyList() : ObservableCollections.observableList(new ArrayList<Something>());

someList.clear();
someList.add(query.getResultList());