我创建了一个小程序，打开JFileChooser以点击JButton选择文件。当我在Eclipse中运行它时，它工作正常。当我将它嵌入带有applet标签的HTML页面时，单击按钮时没有任何反应。
关于为什么JFileChooser无法在浏览器中打开的任何建议都会受到赞赏，但我的主要问题是我该如何调试？我一直无法找到Google上有关如何将Java控制台添加到Firefox 3.6或Chrome的任何内容。有没有办法获得有关JFileChooser无法打开的原因的某种信息？
调试在下面的评论中回答
所以控制台说有一个访问被拒绝的异常，我猜是因为我没有“签署”applet。在签署applet时，开发过程应该是什么？在我可以在浏览器中测试之前，是否必须使用由有效CA颁发的证书对其进行签名，或者在测试时是否可以执行一些简单的操作？
这是我的代码：
package com.putapplet;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.net.URL;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.SwingUtilities;
@SuppressWarnings("serial")
public class PutToS3Applet extends JApplet {
private static long maxFileSizeInBytes = 1048576;
private static String listenerUrl = "xxx";
private String listenerQueryString;
private String signedPutUrl;
private JProgressBar progressBar;
private JButton button;
private JLabel messageField;
public void init() {
setMaxFilesize(1);
try {
SwingUtilities.invokeAndWait(new Runnable() {
public void run() {
createGUI();
}
});
} catch (Exception e) {
System.err.println("createGUI didn't complete successfully");
}
}
private void createGUI() {
button = new JButton("Choose File...");
button.addActionListener(new ButtonListener());
progressBar = new JProgressBar(0, 100);
progressBar.setStringPainted(true);
messageField = new JLabel();
//messageField.setPreferredSize(new Dimension(300, 20));
FlowLayout layout = new FlowLayout();
layout.setAlignment(FlowLayout.LEFT);
JPanel topPanel = new JPanel();
topPanel.setLayout(layout);
JPanel bottomPanel = new JPanel();
bottomPanel.setLayout(layout);
topPanel.add(button);
topPanel.add(progressBar);
bottomPanel.add(messageField);
setLayout(new GridLayout(2,1));
add(topPanel);
add(bottomPanel);
}
class ButtonListener implements ActionListener {
public void actionPerformed(ActionEvent ae) {
JFileChooser fileChooser = new JFileChooser();
int showOpenDialog = fileChooser.showDialog(null, "Upload File");
if (showOpenDialog != JFileChooser.APPROVE_OPTION) return;
final File fileToUpload = fileChooser.getSelectedFile();
if (fileToUpload.length() > PutToS3Applet.maxFileSizeInBytes) {
messageField.setText("Your file must be smaller than " + getHumanReadableMaxFilesize());
return;
}
listenerQueryString = "query[filename]=" + fileToUpload.getName();
//get signed PUT url for s3
try {
URL listener = new URL(listenerUrl + listenerQueryString);
BufferedReader in = new BufferedReader(new InputStreamReader(listener.openStream()));
signedPutUrl = in.readLine().replace("http://", "https://");
messageField.setText(signedPutUrl);
} catch (Exception e) {
messageField.setText("Oops, there was a problem connecting to the server. Please try again.");
e.printStackTrace();
}
}
}
private String getHumanReadableMaxFilesize() {
return Long.toString((PutToS3Applet.maxFileSizeInBytes / 1024 / 1024)) + "MB";
}
private void setMaxFilesize(int sizeInMegaBytes) {
PutToS3Applet.maxFileSizeInBytes = PutToS3Applet.maxFileSizeInBytes * sizeInMegaBytes;
}
}
以下是例外：
Exception in thread "AWT-EventQueue-1" java.security.AccessControlException: access denied (java.util.PropertyPermission user.home read)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:374)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.SecurityManager.checkPropertyAccess(SecurityManager.java:1285)
at java.lang.System.getProperty(System.java:650)
at javax.swing.filechooser.FileSystemView.getHomeDirectory(FileSystemView.java:393)
at javax.swing.plaf.metal.MetalFileChooserUI.installComponents(MetalFileChooserUI.java:253)
at javax.swing.plaf.basic.BasicFileChooserUI.installUI(BasicFileChooserUI.java:136)
at javax.swing.plaf.metal.MetalFileChooserUI.installUI(MetalFileChooserUI.java:126)
at javax.swing.JComponent.setUI(JComponent.java:662)
at javax.swing.JFileChooser.updateUI(JFileChooser.java:1763)
at javax.swing.JFileChooser.setup(JFileChooser.java:360)
at javax.swing.JFileChooser.<init>(JFileChooser.java:333)
at javax.swing.JFileChooser.<init>(JFileChooser.java:286)
at com.putapplet.PutToS3Applet$ButtonListener.actionPerformed(PutToS3Applet.java:82)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
at java.awt.Component.processMouseEvent(Component.java:6289)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
at java.awt.Component.processEvent(Component.java:6054)
at java.awt.Container.processEvent(Container.java:2041)
at java.awt.Component.dispatchEventImpl(Component.java:4652)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4482)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4238)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
at java.awt.Container.dispatchEventImpl(Container.java:2085)
at java.awt.Component.dispatchEvent(Component.java:4482)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:644)
at java.awt.EventQueue.access$000(EventQueue.java:85)
at java.awt.EventQueue$1.run(EventQueue.java:603)
at java.awt.EventQueue$1.run(EventQueue.java:601)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
at java.awt.EventQueue$2.run(EventQueue.java:617)
at java.awt.EventQueue$2.run(EventQueue.java:615)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:614)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
答案 0 :(得分：11)
只是旁注。远程调试applet相当容易。
配置Java插件以允许远程调试。你可以在不同的平台上以不同的方式实现它，但在Windows上它会是这样的。启动控制面板，选择java。单击“开始”直到找到VM选项，然后添加这些VM参数：
-Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,address=6789,suspend=n
6789将是调试端口。
在Eclipse中启动远程调试是通过执行类似的操作来完成的。调试配置，远程Java应用程序，创建新配置。选择Standard（Socket Attach）作为连接类型，输入locahost作为地址，输入6789作为端口。
答案 1 :(得分：2)
考虑启用Java控制台，这将允许您查看所有异常堆栈跟踪，希望您可以更轻松地进行调试。
此外，“appletviewer”旨在测试浏览器之外的applet，包括允许您查看异常。
答案 2 :(得分：1)
你的SecurityManager很可能不允许它。
在FireFox中，您可以转到工具＆gt;查看java控制台。 Java控制台。 Firefox应该已经设置好了。
答案 3 :(得分：0)
答案 4 :(得分：0)
当您在html页面中嵌入applet时，您必须在applet jar文件中签名 请参阅文档 oracle docs
创建您的证书然后使用 然后在命令提示符下键入以下命令
jarsigner jarfilename.jar yourcertificatename