mysql - 如何将 MySQL 中的数据插入数组，然后在 Netbeans 中显示在条形图上？

Question

单击按钮时，我的 graph() 方法需要循环以下行:

ddataset.setValue(new Double(unitsSold), cat, brand + " " + name);

循环次数基于我的数据库的类别列中的项目数。第一项是“电缆”，其中有七项。我想将这些项目中的每一个存储到一个数组中(来自数据库)，然后使用 for 循环 在单个条形图上显示所有这些项目。执行此操作的正确语法是什么？

这是我的graph()方法编码:

public void graph()
    {
        //variable to get the row count
        int x = 0;
        try
        {
            //declaring the type of category in the column
            String text = "Cable";
            //Select statement getting the row count
         String sql = "select count(category) from dbsales where category ='" + text + "'";
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = (Connection)
            DriverManager.getConnection("jdbc:mysql://localhost:3306/salventri","root","password");
            Statement stmt=con.createStatement();
            ResultSet rs = stmt.executeQuery(sql); 

            while(rs.next())
            {
                //setting 'x' with the row count
               x = rs.getInt("count(category)");
                           DefaultCategoryDataset ddataset = new DefaultCategoryDataset();
            //loop the data according to x value
            for(int i = 0; i < x; i++)
            { 
                    ddataset.setValue(new Double(unitsSold), cat, brand + " " + name);
             }
             JFreeChart chart = ChartFactory.createBarChart3D("Annual Sales Performance", cat, "Number of Units Sold", ddataset);
            chart.getTitle().setPaint(Color.RED);
            CategoryPlot p = chart.getCategoryPlot();
            p.setRangeGridlinePaint(Color.BLUE);
            ChartFrame frame2 = new ChartFrame("Annual Sales", chart);
            frame2.setVisible(true);
            frame2.setSize(450,350);
        } 

Answer 1

这是唯一对我有意义的事情。不需要计数查询或将类别放入数据中，因为整个图表都是针对该类别的。除非您想对所有年份求和，否则年份确实需要包含在数据中。

PreparedStatement stmt = con.prepareStatement("select * from dbsales where category=?");
stmt.setString(1, text);
ResultSet rs = stmt.executeQuery();
DefaultCategoryDataset ddataset = new DefaultCategoryDataset();
while (rs.next()) {
    ddataset.setValue(new Double(rs.getDouble("usold")),
            rs.getString("pbrand") + " " + rs.getString("pname"),
            rs.getString("syear"));
}
JFreeChart chart = ChartFactory.createBarChart3D("Annual Sales Performance", text, "Number of Units Sold", ddataset);
chart.getTitle().setPaint(Color.RED);
CategoryPlot p = chart.getCategoryPlot();
p.setRangeGridlinePaint(Color.BLUE);
ChartFrame frame2 = new ChartFrame("Annual Sales", chart);
frame2.setVisible(true);
frame2.setSize(450, 350);

应该产生这样的东西: