Question

我有一个编辑例程，允许我创建，编辑和保存特定数据库的记录。在这个例程中，我有一个jlable用于显示一个图像（imageIcon），在初始创建或记录编辑每个记录时从磁盘文件加载。没有probs。

我需要将imageIcon不是磁盘文件（以及该特定记录的所有相关数据）并将其存储在嵌入式数据库（图像的blob类型）中。除了图像存储之外，数据库已经创建，初始化和工作。

存储图像后，当访问每个记录时，jlable将显示存储在数据库中的图像。原始磁盘文件（JPG，PNG，ect）将无法加载。在初始创建记录之后，只有当用户希望将图像更改为其他图像时，才会使用磁盘文件。

简单地说 - 两个例程： 1.获取imageIcon，将其保存到数据库blob中。 2.检索数据库blob并将其显示到imageIcon。

Answer 1

我很抱歉回答你的问题为时已晚，因为我刚刚开始使用Derby（我在Derby之前使用过MySQL）。此代码从JButton图标中保存BLOB，该图标取自JFileChooser对话框。代码是keyfield，表的主键和 field是表示BLOB字段名称的字符串。图片从路径目录中选择：

 public void SearchAndSave(JButton tombol) throws FileNotFoundException, 
 SQLException, IOException {

    //  set default directory from JFileChooser 

    JFileChooser fc = new JFileChooser(Path);
    fc.setAccessory(new ImagePreviewComponent(fc));      
    int returnVal = fc.showOpenDialog(null);
    if (returnVal == JFileChooser.APPROVE_OPTION) {
        File file = fc.getSelectedFile();
        String dir = file.getAbsolutePath();
        ImageIcon icon = new ImageIcon(dir);
        String fname = file.getName();                                                       
        tombol.setText("");  // tombol is JButton                 
        tombol.setIcon(icon);                                
        fileinputstream = new FileInputStream(file);
        String simpan = JOptionPane.showInputDialog("Save image ? ((y/n))");
        if (simpan.equals("y")) {
            PreparedStatement ps = null;
            Connection con = Database.getConnection();
            String SQL = "INSERT INTO " + namatabel; // name of table

            SQL = SQL + " (" + keyfield + "," +field + ") ";                        
            SQL = SQL + "VALUES (?,?)";
            ps = con.prepareStatement(SQL);

            try {               
                ps.setString(1, code);
                Blob blob = con.createBlob();                  
                ObjectOutputStream oos;
                oos = new ObjectOutputStream(blob.setBinaryStream(1));
                oos.writeObject(icon);
                oos.close();
                ps.setBlob(2, blob);                      
                if (ps.executeUpdate() > 0)                       
                    JOptionPane.showMessageDialog(null, "Image is saved");                                       
                else
                    JOptionPane.showMessageDialog(null, "Not saved");     
                blob.free();
                ps.close();
            } 
            catch(SQLException e) {   
                if (e.getErrorCode() == 1406) {
                    String msg = "Image size is too big";                  
                    JOptionPane.showMessageDialog(null, msg);
                }
                e.printStackTrace();                
            }
        }                         
    }        
 }

这是ImagePreviewcomponent类：

 package util;
 import java.awt.Dimension;
 import java.awt.Graphics;
 import java.awt.Image;
 import java.beans.PropertyChangeEvent;
 import java.beans.PropertyChangeListener;
 import java.io.File;
 import javax.swing.ImageIcon;
 import javax.swing.JComponent;
 import javax.swing.JFileChooser;
 public class ImagePreviewComponent extends JComponent implements 
 PropertyChangeListener {
 ImageIcon thumbnailImage = null;
 File file = null;
 Double widthBox = 100.0;
 Double heightBox = 100.0;

public ImagePreviewComponent(JFileChooser fc) {
    setPreferredSize(new Dimension(widthBox.intValue(), heightBox.intValue()));
    fc.addPropertyChangeListener(this);
}

public double getBestScale(ImageIcon imageIcon) {
    double bestScale;
    if ((widthBox >= imageIcon.getIconWidth()) && (heightBox >= imageIcon.getIconHeight())) {
        bestScale = 1;
    } else {
        double widthScale = widthBox / imageIcon.getIconWidth();
        double heightScale = heightBox / imageIcon.getIconHeight();

        if (widthScale > heightScale) {
            bestScale = heightScale;
        } else {
            bestScale = widthScale;
        }
    }
    return bestScale;
}

public void propertyChange(PropertyChangeEvent e) {
    String prop = e.getPropertyName();
    if (JFileChooser.DIRECTORY_CHANGED_PROPERTY.equals(prop)) {
        file = null;
    } else if (JFileChooser.SELECTED_FILE_CHANGED_PROPERTY.equals(prop)) {
        file = (File) e.getNewValue();
    }

    if (file == null) {
        thumbnailImage = null;
    } else {
        ImageIcon imageIcon = new ImageIcon(file.getPath());
        double bestScale = getBestScale(imageIcon);
        thumbnailImage = new ImageIcon(imageIcon.getImage().getScaledInstance(
                (int) ((double) imageIcon.getIconWidth() * bestScale),
                (int) ((double) imageIcon.getIconHeight() * bestScale),
                Image.SCALE_DEFAULT));
    }
    repaint();
}

@Override
protected void paintComponent(Graphics g) {
    if (thumbnailImage != null) {
        int x = getWidth() / 2 - thumbnailImage.getIconWidth() / 2;
        int y = getHeight() / 2 - thumbnailImage.getIconHeight() / 2;
        thumbnailImage.paintIcon(this, g, x, y);
    }
}
}

您可以尝试使用此网站检索BLOB：http://www.jguru.com/faq/view.jsp?EID=1325#。

检索并更新java derby数据库博客项

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