java - servlet 中后台的路径

Question

//下面的行是我的 HTML 表单的元素，它呈现由下面进一步编写的 servlet 发送的图像。

  <img style="margin-left:91px; margin-top:-6px;" class="image" src="http://www.abcd.com/captchaServlet"> 

我在 java 中使用以下代码生成验证码。

public class captchaServlet extends HttpServlet {


  protected void processRequest(HttpServletRequest request, 
                                HttpServletResponse response) 
                 throws ServletException, IOException {

    int width = 150;
    int height = 50;
    int charsToPrint = 6;

     String elegibleChars = "ABCDEFGHJKLMPQRSTUVWXYabcdefhjkmnpqrstuvwxy1234567890";

     char[] chars = elegibleChars.toCharArray();
StringBuffer finalString = new StringBuffer();

   for ( int i = 0; i < charsToPrint; i++ ) {
     double randomValue = Math.random();
     int randomIndex = (int) Math.round(randomValue * (chars.length - 1));
     char characterToShow = chars[randomIndex];
     finalString.append(characterToShow);
   }
   System.out.println(finalString);

    BufferedImage bufferedImage = new BufferedImage(width, height, 
                  BufferedImage.TYPE_INT_RGB);

    Graphics2D g2d = bufferedImage.createGraphics();

    Font font = new Font("Georgia", Font.BOLD, 18);
    g2d.setFont(font);

    RenderingHints rh = new RenderingHints(
           RenderingHints.KEY_ANTIALIASING,
           RenderingHints.VALUE_ANTIALIAS_ON);

    rh.put(RenderingHints.KEY_RENDERING, 
           RenderingHints.VALUE_RENDER_QUALITY);

    g2d.setRenderingHints(rh);

    GradientPaint gp = new GradientPaint(0, 0, 
    Color.BLUE, 0, height/2, Color.black, true);

    g2d.setPaint(gp);
    g2d.fillRect(0, 0, width, height);

    g2d.setColor(new Color(255, 255, 0));

    Random r = new Random();
    int index = Math.abs(r.nextInt()) % 5;
    char[] data=new String(finalString).toCharArray();
    String captcha = String.copyValueOf(data);
    int x = 0; 
    int y = 0;

    for (int i=0; i<data.length; i++) {
        x += 10 + (Math.abs(r.nextInt()) % 15);
        y = 20 + Math.abs(r.nextInt()) % 20;
        g2d.drawChars(data, i, 1, x, y);
    }

    g2d.dispose();

    response.setContentType("image/png");
    OutputStream os = response.getOutputStream();
    ImageIO.write(bufferedImage, "png", os);
    os.close();
  } 


  protected void doGet(HttpServletRequest request, 
                       HttpServletResponse response)
                           throws ServletException, IOException {
      processRequest(request, response);
  } 


  protected void doPost(HttpServletRequest request, 
                        HttpServletResponse response)
                            throws ServletException, IOException {
      processRequest(request, response);
  }
}

但在上面的代码中，我猜测背景也是使用 setPaint 方法生成的。我希望背景是来 self 的本地计算机的一些图像，我应该能够提及该图像

URL url=this.getClass().getResource("Desktop/images.jpg");
BufferedImage bufferedImage = ImageIO.read(url);

我写上面两行只是为了让读者更好地理解问题所在。不想使用完全相同的命令。我想要的只是生成的验证码的背景应该是我选择的图像。

Answer 1

而不是调用

g2d.setPaint(gp);
g2d.fillRect(0, 0, width, height);

您可能需要调用类似以下内容的内容:

g2d.drawImage(bufferedImage, 0, 0, null);