无法恢复 URL 存储在 MySQL 数据库中

Question

我正在编写一个应用程序，将用户的头像存储在mysql数据库中，由于BLOB和CLOB数据类型带来的性能下降，我决定不使用它们，而是存储数据库 table 中的图像 url 作为 varchar 值。

问题是：当我尝试使用 ResultSet.getURL() 方法甚至 resultSet.getString() 检索 url 时。我收到 MalformedURLException- "Protocol :C not recognised"。我该如何解决这个问题，请帮忙。

这是我的代码；

 try {
        sqlConnectionObject = DriverManager.getConnection(jdbcUrl,"root","");
    } catch (SQLException ex) {
        Logger.getLogger(Androbot.class.getName()).log(Level.SEVERE, null, ex);
    }
    fileChooser = new JFileChooser();
    FileFilter fileFilter = new FileNameExtensionFilter("pic", "jpg");
    fileChooser.addChoosableFileFilter(fileFilter);

    obtainURLFromDBButton.addActionListener(
            new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent event) {
            try {
                JOptionPane.showMessageDialog(null, obtainImageUrl("userName"));
                File file = new File(obtainImageUrl("userName").toString()); //the obtain image url 
                                                                             //function is called  here
                                                                             //and passed to File
                                                                             //file is used to creat image
                Image img = ImageIO.read(file);
                thisButton.setIcon(new ImageIcon(img));
            } catch (FileNotFoundException e) {
                JOptionPane.showMessageDialog(null, "ERROR" + e.getMessage());
            } catch (IOException e) {
                JOptionPane.showMessageDialog(null, "ERROR" + e.getMessage());
            }
        }
    }
    );

//Allows user to set profile
    addImagButton.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent event) {
            int ret = fileChooser.showDialog(null, "Add Profile Picture");
            if (ret == JFileChooser.APPROVE_OPTION) {
                // fileChooser.getSelectedFile().getPath();
                try {
                    // file = new File("C:\Users\user\Pictures\EmmaBeib\12553040_133350150376029_4407158756206009973_n.jpg");
                    String fileUrl = fileChooser.getSelectedFile().getPath();
                    JOptionPane.showMessageDialog(null,"URL = "+fileUrl);
                    addURLRow("userName", fileUrl);
                    image = ImageIO.read(fileChooser.getSelectedFile());

                    addImagButton.setIcon(new ImageIcon(image));
                  //  addPictureToDB(fileChooser.getSelectedFile());
                } catch (FileNotFoundException e) {
                    System.err.println(e);
                } catch (IOException e) {
                    System.out.println(e);
                }catch(SQLException e){
                    JOptionPane.showMessageDialog(null,"ERROR"+e.getMessage());
                }

            } else if (ret == JFileChooser.CANCEL_OPTION) {
                int opt = JOptionPane.showConfirmDialog(null, "Apopprove cancel?", "", JOptionPane.OK_CANCEL_OPTION);
                if (opt == JOptionPane.CANCEL_OPTION) {
                    fileChooser.showDialog(null, "Add Profile Picture");
                }
            } else if (ret == JFileChooser.ERROR_OPTION) {
                JOptionPane.showMessageDialog(null, "An ERROR occured try again later");

            }
        }
    }
    );

//Obtain picture from the database
public Object obtainImageUrl(String userName) throws MalformedURLException {
    try (Connection connect = DriverManager.getConnection("jdbc:mysql://localhost:3306/picturedb", "root", "")) {
        Statement mysqlStm = connect.createStatement();
        String SELECT_QUERY = "SELECT * FROM picture WHERE userName IN ('" + userName + "');";
        ResultSet cursor = mysqlStm.executeQuery(SELECT_QUERY);
        while (cursor.next()) {
            imageUrl = cursor.getObject("picUrl");
        }
        URL url = new URL(imageUrl.toString());
        // File imageFile = new File(imageUrl);
        try {
            Image img = ImageIO.read(url);

        } catch (IOException ex) {
            JOptionPane.showMessageDialog(null, "ERROR" + ex.getMessage());
        }

    } catch (SQLException e) {
        JOptionPane.showMessageDialog(null, "ERROR" + e.getMessage());
    }
    return imageUrl;
}
 //insert image url in the db
public void addPictureToDB(File file) {
    imageUrl = file.getAbsolutePath();
    try (Connection connect = DriverManager.getConnection(jdbcUrl, "root", "")) {
        Statement mysqlStmt = connect.createStatement();
        String INSERT_QUERY = "INSERT INTO picture VALUES('"
                + imageUrl + "','"
                + "BETTY KIPPO');";
        mysqlStmt.execute(INSERT_QUERY);
        JOptionPane.showMessageDialog(null, "Image Added Succefully");
    } catch (SQLException e) {
        JOptionPane.showMessageDialog(null, "ERROR" + e.getMessage());
    }
}

Answer 1

通过研究和实验，我发现当我使用

JFileChooser fileChooser = new JFileChooser();
fileChooser.getSelectedFile().getPath().toString();

这样发送到数据库的路径字符串是有效的url，因此我不需要更改正在使用 onRetrieve 的协议。

无法恢复 URL 存储在 MySQL 数据库中

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