在浏览器中调试 Java 小程序 - 可在 Eclipse 中运行，但不能在浏览器中运行 [英] Debugging java applet in browser - works in Eclipse but not browser
问题描述
我创建了一个小程序，它打开一个 JFileChooser 以通过点击 JButton 来选择一个文件.当我在 Eclipse 中运行它时它工作正常.当我将它嵌入带有小程序标记的 HTML 页面时，当我单击按钮时没有任何反应.
I have created an applet that opens a JFileChooser to select a file on the click of a JButton. It works fine when I run it in Eclipse. When I embed it in an HTML page with the applet tag nothing happens when I click the button.
关于为什么 JFileChooser 没有在浏览器中打开的任何建议将不胜感激，但我的主要问题是我将如何调试?我还没有能够在 Google 上找到有关如何将 Java 控制台添加到 Firefox 3.6 或 Chrome 的任何信息.有没有办法获取有关 JFileChooser 为何无法打开的某种信息?
Any suggestions as to why the JFileChooser does not open in the browser would be appreciated, but my main question is how would I debug this? I haven't been able to find anything on Google about how to add a Java console to Firefox 3.6 or Chrome. Is there a way to get some kind of information as to why the JFileChooser does not open?
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，我猜这是因为我没有签署"小程序.就签署小程序而言，开发过程应该是怎样的?在我可以在浏览器中测试它之前，我是否必须使用有效 CA 颁发的证书对其进行签名，或者您可以在测试时做一些简单的事情吗?
So the console says there is an access denied exception, which I'm guessing is because I have not "signed" the applet. What should the development process be as far as signing an applet goes? Do I have to sign it with a certificate issued by a valid CA before I can test it in a browser, or is there some simple thing you can do while just testing?
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;
}
}
这里有一个例外:
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)
推荐答案
只是一个旁注.远程调试小程序相当容易.
Just a side note. It's rather easy to remote debug applets.
配置 Java 插件以允许远程调试.你在不同的平台上以不同的方式做这件事，但在 Windows 上会是这样.启动控制面板，选择java.单击周围直到找到 VM 选项，然后添加这些 VM 参数:
Configure the Java plugin to allow remote debugging. You do it in different ways in different platforms, but it will be something like this on windows. Start the control panel, select java. Click around till you find VM options, and add these VM arguments:
-Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,address=6789,suspend=n
6789 将是调试端口.
6789 will be the debug port.
在 Eclipse 中启动远程调试是通过做类似的事情来完成的.调试配置、远程 Java 应用程序、创建新配置.连接类型选择标准(Socket Attach)，地址输入locahost，端口输入6789.
Starting the remote debugging in Eclipse is done by doing something similar to. Debug configurations, Remote Java Application, Create a new configuration. Select Standard (Socket Attach) as connection type, and enter locahost as address and 6789 as port.
这篇关于在浏览器中调试 Java 小程序 - 可在 Eclipse 中运行，但不能在浏览器中运行的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
