Question

我正在尝试从applet编写示例文件但是无法正常工作。以下是代码。

小程序

public class PasteImageApplet extends JApplet {

    Clipboard clipboard;
    Toolkit toolkit;
    JLabel lbl;

    public String getClipboardImageURL(String server) {
        lbl.setText("pasting image");

        String url = "";
        try {
            DataFlavor dataFlavor = DataFlavor.imageFlavor;
            System.out.println(dataFlavor.getDefaultRepresentationClass());
            Object object = null;

            try {
                object = clipboard.getContents(null)
                        .getTransferData(dataFlavor);
                JOptionPane.showMessageDialog(null,"Image found.");
                try
                {
                Writer output = null;
                String text = "Test Write File";
                File file = new File("write.txt");
                output = new BufferedWriter(new FileWriter(file));
                output.write(text);
                output.close();
                }
                catch(Exception ex)
                {
                    JOptionPane.showMessageDialog(null,"Error writing file"+ex);
                    return "" ;
                }
                //return "";
            } catch (Exception e) {
                JOptionPane.showMessageDialog(null, "No image found.");
                return "";
            }
        } catch (Exception e) {
            JOptionPane.showMessageDialog(null, "Error."+e);
            return "";
        }

         return url;
    }

    public void init() {
        lbl = new JLabel("");
        lbl.setText("applet started");
        add(lbl);
        toolkit = Toolkit.getDefaultToolkit();
        clipboard = toolkit.getSystemClipboard();
    }
}

HTML

<html>
    <head>
        <title>Clipboard image demo</title>

        <script type="text/javascript">
            function loadApplet() {
                // Deferred load to display text first
                document.getElementById("applet").innerHTML = '<object id="paste-image" classid="java:PasteImageApplet.class" type="application/x-java-applet" archive="tst.jar" width="1" height="1"></object>';
            }

            function getImage() {
                obj = document.getElementById('paste-image');
                postTo = "http://localhost/PasteImageApplet/PasteImageApplet/Web/shoot.php"; // Change this to your URL

                image = obj.getClipboardImageURL(postTo);

                if (image) {
                    url = "shots/" + image;

                    document.getElementById("target").src = url;
                    document.getElementById("url").value = document.getElementById("target").src; // to get full path, hack, I know ;)
                    document.getElementById("container").style.display = "";
                }
            }
        </script>

        <body onload="loadApplet();">

            <p>
                Copy some image data to your clipboard, accept the applet (it only accesses the clipboard) and click the button :-)
                <a href="http://lassebunk.dk/2009/07/19/using-the-clipboard-to-post-images/">See a blog post about this demo</a>
            </p>

            <p>
                <div id="applet"></div>
                <input type="button" value="Paste it!" onclick="getImage();">
            </p>

            <div id="container" style="display: none;">
                <input type="text" id="url" style="width: 700px;"><br />
                <iframe id="target" width="700" height="400"></iframe>
            </div>

    </body>
</html>

我也没有收到任何错误。请指教。

Answer 1

那是因为applet存在自己的沙箱，在那里他们需要特殊的权限来执行某些操作，比如读取或写入客户机的磁盘。请记住，applet在客户端计算机的上下文中执行，他们是访客，需要遵守内部规则

查看What Applets can and cannot do了解详情

Answer 2

小程序无法在服务器上建立File。这不是服务器的工作方式。如果服务器接受上传，它必须提供特定的功能来启用它，并且applet必须使用该功能。

只要接受上传的功能在同一台服务器上，applet就可以保持沙盒状态。

Answer 3

你可以通过（windows）任务栏看到applet的控制台，你右键单击java图标（当applet运行时它应该出现在右下方）并右键单击＆gt;打开控制台，你可以在那里调试，这是applet的堆栈跟踪的地方。

小程序 - 无法写入文件

3 个答案: