xp演示如何将映像返回到java的<xp:image>url而不保存到磁盘

Question

java方面的工作很少，有必要向xpages添加验证码。 java中有一个代码：

public static void getImage() {
                    String text = "Hello";
                    BufferedImage img = new BufferedImage(1, 1, BufferedImage.TYPE_INT_ARGB);
                    Graphics2D g2d = img.createGraphics();
                    Font font = new Font("Arial", Font.PLAIN, 48);
                    g2d.setFont(font);
                    FontMetrics fm = g2d.getFontMetrics();
                    int width = fm.stringWidth(text);
                    int height = fm.getHeight();
                    g2d.dispose();

                    img = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
                    g2d = img.createGraphics();
                    g2d.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
                    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
                    g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
                    g2d.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
                    g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
                    g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
                    g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
                    g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);
                    g2d.setFont(font);
                    fm = g2d.getFontMetrics();
                    g2d.setColor(Color.BLACK);
                    g2d.drawString(text, 0, fm.getAscent());
                    g2d.dispose();
                    try {
                        ImageIO.write(img, "png", new File("c:\\Text.png"));
                    } catch (IOException ex) {
                        ex.printStackTrace();
                    }

应该对插入到<xp:image>中的图像执行什么操作

Answer 1

您可以创建一个XAgent，它调用getImage（）方法将URL返回到xp:image

下面是一个XAgent的示例：

<?xml version="1.0" encoding="UTF-8"?>
<xp:view xmlns:xp="http://www.ibm.com/xsp/core" xmlns:xc="http://www.ibm.com/xsp/custom" rendered="false" viewState="nostate">

    <xp:this.beforeRenderResponse><![CDATA[#{javascript:
        com.company.getImage();
    }]]></xp:this.beforeRenderResponse>

</xp:view>

您需要修改getImage（）方法以流式返回图像。下面是一个示例（未测试）：

public static void getImage() {
    try {
        HttpServletResponse response = (HttpServletResponse) FacesContext.getCurrentInstance().getExternalContext().getResponse();
        ServletOutputStream responseStream = response.getOutputStream();

        // Add your existing code to create your image here

        // Write the image to the responseStream
        ImageIO.write(img, "png", responseStream);

        FacesContext.getCurrentInstance().responseComplete();
        responseStream.close();
    } catch (IOException ioe) {
        ioe.printStackTrace();
    }
}

然后在xp:image中使用XAgent，如下所示（假设它被称为image.xsp）：

<xp:image>
    <xp:this.url><![CDATA[#{javascript:"/image.xsp"}]]></xp:this.url>
</xp:image>