Java Plug-in Software 1.3 Troubleshooting FAQ

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        General Troubleshooting Issues
        Troubleshooting Installation Issues
        Troubleshooting Security Issues

General Troubleshooting Issues   back to top  

Q: How do I get Netscape to find my plugin when I've downloaded and installed the J2SE, including the Plugin?

A: Just set the NPX_PLUGIN_PATH environment variable to the location of the Java Plug-in (the directory in which the file is located): NPX_PLUGIN_PATH=$JAVAHOME/jre/plugin/sparc

Q: I can't get Java Plug-in 1.3 software to install via an intranet by placing it on our Netscape Enterprise 3.0 SuiteSpot web server. Why not?

A: We've got reports that the Netscape Enterprise 3.0 SuiteSpot Webserver is unable, at least in some circumstances, to serve up .exe files. One workaround that has seemed to work is to configure the HTML so that the Java Plug-in product is installed by a Visigenic Orb Gatekeeper, which also functions as a web server.

Q: I'm having trouble debugging with Java Plug-in Software. Do you have any tips?

A: In some circumstances, Java Plug-in Software will use a different debug connection address than expected. This occurs when Java Plug-in Software is loaded into the Explorer.exe process running in one of the following configurations:

  • Windows 95/NT running Active Desktop with IE4 or later
  • Windows 98
  • Windows 2000 (currently tested with RC1)

Java Plug-in Software is loaded into the Explorer.exe process when an HTML page containing the OBJECT tag is viewed in the following ways:

  • via preview in an Explorer folder, if the desktop settings allow web content to be viewed in folders (in other words, if the View->As Web Page menu option is checked)
  • via Internet Explorer, if the Microsoft Internet settings for "Launch browser windows in a separate process" or "Browse in a new process" are not set
  • via a webpage shown on the Active Desktop

This can cause problems when debugging Java applets, since no two processes should use the same debug connection address (found on the Advanced tab of the Java Plug-in Software control panel under Debug Settings). If the Explorer.exe process has already claimed the debug connection address, and the Netscape.exe or Iexplorer.exe tries to use it, debugging problems may result.

Java Plug-in Software avoids this complication when loaded into the Explorer.exe process by prepending the debug connection address specified in the control panel witht he string Explorer.

For example, if the default connection address set at the time of Java Plug-in Software installation is 2502, when running under Explorer.exe it is actually set to Explorer:2502.

When running JDB from the Java 2 SDK, you should specify


jdb -attach Explorer:2502

to attach to the JVM loaded into the Explorer.exe process.

Q: Why can I not get the examples or the control panel to work for Java Plug-in Software?

A: In order to use the control panel or the example applets, you need to enable Javascript in your browser.

Q: My applet no longer works in Internet Explorer with Java Plug-in Software 1.3. Why?

A: With Java Plug-in Software 1.3 a new PARAM scriptable tag was introduced. This tag must be included and given a value of "true" in order for an applet to be scriptable. See the HTML Specification for more information.

Q: Why am I having problems using some standard extensions/optional packages?

A: In Java Plug-in Software 1.3, only extensions installed in the <jre>\lib\ext directory will be added to the classpath. Extensions installed in directories pointed to by the java.ext.dirs system property will not be added.

Q: Java Plug-in Software 1.3 used to work with my Navigator 4.0.x browser. But when I upgraded to Navigator 4.5 and re-installed Java Plug-in Software 1.3, Java Plug-in Software does not work with Navigator 4.5. Why?

A: It has been reported that Navigator 4.5 may not install the user profile properly during installation. As a result, Java Plug-in Software may not read the correct user profile setting. To make sure the user profile setting is correct, please check the following:

  • HKEY_LOCAL_MACHINE\Software\Netscape\Netscape Navigator\Users\CurrentUser
  • HKEY_LOCAL_MACHINE\Software\Netscape\Netscape Navigator\Users\<UserName>\DirRoot

Q: It has been reported that Java Plug-in Software 1.1. x does not work well with Navigator 4.5 because of a system resource conflict. Is this problem resolved in Java Plug-in Software 1.3?

A: Yes. The system resource conflict has been resolved in Java 2 SDK, Standard Edition/JRE v 1.3 which includes Java Plug-in Software 1.3.

Q: My Swing applet used to work in Java Plug-in Software 1.1. x. After I upgraded to Java Plug-in Software 1.3, it doesn't work any more. Why?

A: Java Plug-in Software 1.1.1 includes Swing 1.0.3, which supports the package name com.sun.swing.*. Now Java Plug-in Software 1.3 includes Swing 1.1 which supports the new package javax.swing.*. As a result, any attempt to run the old Swing applet in Java Plug-in Software 1.3 will result in java.lang.NoClassDefFoundError. This problem can be resolved by migrating your Swing applet to the new javax.swing package name.

Q: We are trying to use Java 3D with Java Plug-in Software, but it doesn't work at all. Why?

A: Java 3D comes with various packages. Installing it incorrectly may inadvertently disable Java Plug-in Software or cause it to fail. Follow these general instructions for using Java 3D and Java Plug-in Software:

  1. Install Java Plug-in Software first.
  2. Install Java 3D in a new directory. Do not install it over the existing Java 2 SDK, Standard Edition/JRE. See this page for installation instructions.
  3. In the Java Plug-in Software control panel, switch the JRE to the one that came with Java 3D.
  4. Download the HTML Converter 1.3 and convert the Java 3D demo pages.

Q: Some web/proxy server require users to login for authentication. When I used the browser to access this server with Java Plug-in Software, two login dialog boxes appeared. Why?

A: Normally Java Plug-in Software will download the applet or Bean using its own connection. If the web/proxy server requires a login, the browser will first encounter the request and bring up a login dialog box. After the HTML page is downloaded, Java Plug-in Software will try to download the class or jar files for the applet. However, since Java Plug-in Software has no access to the login information that the browser previously obtained, it will bring up its own login dialog box.

Q: My signed applet is working fine in Java 2 SDK, Standard Edition/JRE AppletViewer. However, after I start using Java Plug-in Software in Internet Explorer or Netscape Navigator, it stops working. What's going on? 

A: AppletViewer and Java Plug-in Software look for the identitydb.obj file in different locations. Please make sure the identitydb.obj file is in the right location when running Java Plug-in Software.

In other cases, the applet fails in Java Plug-in Software because Java Plug-in Software runs applets in untrusted mode. To test this properly in AppletViewer, always specify an http URL if possible. If this is not possible, make sure the applet classes are not in your CLASSPATH and use a file URL.

Q: When I tried to deploy Java Plug-in Software in the intranet and put the binaries in the internal web server, IE doesn't download and install Java Plug-in Software when it encounters the converted page. What's going on? 

A: You may want to check that the CODEBASE in the OBJECT tag actually has the correct URL for the Java Plug-in Software. Also, turning off execute privileges on the directory in which you put the Java Plug-in Software executable may help.

Q: I am experiencing problems getting an applet to render using Java Plug-in Software. What is the cause of this?

A: While this may be due to a variety of circumstances unique to your operating environment, two frequent causes of this problem and the requisite workarounds are provided below:

Scenario 1: Security Exception

I am using Java Plug-in Software and each time I try to load an applet on a web page that specifies the Java Plug-in Software, when the applet is loaded, a SecurityException is triggered.

Problem: Your network does not support DNS (Domain Name Service). In order to perform certain security checks, the Applet SecurityManager needs to be able to find the IP address from which your applet was downloaded. If DNS is not available, these security checks may fail.

Workaround: When visiting the target web page, specify an IP address rather than a hostname in the URL. For example, use "".

Scenario 2: Applet does not start using IE 3.02 and NT 4.0

I am using Java Plug-in Software to run the demos on Sun's web site, using Internet Explorer 3.02 on Windows NT 4.0. Instead of rendering the applet, the browser displays a message that says "Your browser understands the <APPLET> tag but is not running the applet for some reason"

Problem: This is caused by an installation bug in Internet Explorer 3.02. When you install Internet Explorer 3.02 on Windows NT 4.0, some of the settings are stored in the HKEY_CURRENT_USER in the Windows registry. However, when you login to Windows NT using another user account, these settings in the registry can no longer be accessed because they are in a different user account.

Workaround: Either reinstall Internet Explorer 3.02 in the current user account, or install Internet Explorer 4.

Q: I changed my browser setting while Java Plug-in Software was running, but it still uses the old settings after the change. Why?

A: The browser settings are read in by Java Plug-in Software when it is started. These settings are valid throughout the lifetime of the browser session. To make Java Plug-in Software read in the new settings, simply restart your browser. If you running Active Desktop with Java Plug-in Software, you need to restart the machine.

Q: Using Navigator, when I print a web page that contains an applet using Java Plug-in Software, the applet does not show up in the printout. Why?

A: This is caused by a bug in the Java Plug-in Software API in Navigator 4.0 and later. There is currently no workaround to this problem.

Q: When I loaded my applet, it said "noninit" or "applet not initialized" in the browser's status bar. How can I identify the cause of the problem?

A: Follow these steps:

  1. Select Java Console from the Java Plug-in Software Control Panel and run the applet again.
  2. Look at the error message in the Java Console.
  3. If you are accessing the applet through the network, make sure the proxy info shown in the Java Console is correct.
  4. Make sure all the class/JAR files are in the right directory.
  5. Make sure the converted HTML page is correct.
  6. Try the unconverted page with AppletViewer on the same machine. If it works, please recheck 3, 4, and 5 again.

Q: After I install Java Plug-in Software, why won't the Win32 Java Plugin Software load in Navigator?

A: It may be that installation of Java Plug-in Software didn't complete successfully. Make sure the file NPJava32.dll is in the Plugin directory. Otherwise, just copy it from the PlugJava Plugin Software/bin directory, and it should work.

Q: When using Java Plug-in Software 1.3 or the HTML Converter 1.3 on a Japanese version of Windows98, the system is unstable. Is there a solution?

A: This problem is caused by bugs in the Input Method Editor (IME) that comes with Windows98. Install the Input Method Editor Service Release 1 (IME-SR1) for Windows98 from Microsoft before running Java Plug-in Software 1.3 or the HTML Converter 1.3.

Q: When I try to use the AppletClassLoader with Java Plug-in Software 1.3, it crashes with a null pointer exception in IE4, but works fine in Netscape. Why does this happen? Is there a way to make it work correctly in IE4?

A: Java Plug-in Software 1.3 in IE4 tries to load < YourAppletName>BeanInfo.class even if your applet is not a bean. There is a bug in Java 2 SDK, Standard Edition v 1.3 in the AppletClassLoader that occurs when trying to load nonexistent classes. To prevent this problem, create an empty < YourAppletName>BeanInfo.class.

Q: Why does Java Plug-in Software sometimes crash Internet Explorer, but not Netscape Navigator?

A: In certain circumstances, bad HTML will cause the browser to crash. One example is the absence of an </XMP> tag. Please make sure your HTML is correct.

Another possibility is that the plug-in was disabled using the control panel before you accessed a plug-in enabled page. Please check your settings to make sure the plug-in is enabled.

Q: My applet used to create a top level frame that would remain visible through page switches. When I upgraded to Java Plug-in Software 1.3 this no longer occurs. Why?

A: In Java Plug-in Software, applets are stopped and destroyed during page switches. All the visible components should be destroyed as well. There has been an enhancement in Java 2 SDK, Standard Edition/JRE 1.3 that makes sure that all of the resources of the applet are properly released, including the top level frame.

Troubleshooting Installation Issues   back to top  

Q: When I unzip the HTML Converter, all the files are 0 bytes. What is going on?

A: Unzipping the HTML Converter requires the latest version of Winzip (6.2 or later). Using earlier versions of Winzip may not unzip the Converter properly.

Q: I cannot unzip the HTML Converter zip file. Why not?

A: This file is actually a jar file. To uncompress the file type jar -xvf zip file at the command line. If you want to use a compression program, we recommend the latest version of WinZip.

If your experience problems unzipping the files, make sure you have the most recent version of your compression utility. Older versions may not be able to handle long filenames.

Q: The file Java Runtime Environment 1.3.1_0x (an ActiveX Control) in the WINNT/Downloaded Program Files directory says it's "Damaged." What does this mean? What can I do about it?

A: This is a cosmetic bug; you won't run into any actual problems with the Java Runtime Environment. It does not mean that anything is damaged or that the installation failed. However, if you would still like to make it read "installed" instead of "damaged", you can edit the windows registry. First double-click on the ActiveX Control that is "damaged" ( Java Runtime Environment 1.3.1_0x) and check the ID value. Go to Start->Run, type regedit and hit "Ok". Traverse to the following registry key: HKEY_LOCALE_MACHINE//Software//Microsoft//Code Store
Database//Distribution Units//{ID}//DownloadInformation
, where ID is the value of the ID. Double click on the INF registry string, delete the string contents, and hit "Ok". The status of the previously "damaged" ActiveX control should now say "installed".

Q: I am trying to install the Java Plug-in Software in a network drive. However, it doesn't install. Why? 

A: If your network drive is protected or read-only, you will not be able to install the Java Plug-in Software. Please contact your system administrator for more details.

Q: I am trying to install Java Plug-in Software. However, whenever the install program tries to install the Java Plug-in Software for Netscape Navigator, it displays an error. My Navigator is on a network drive. Is there a way to fix this? 

A: If your Navigator is installed on a network drive, you may not have the permission to install the plugin DLL into the Navigator Plugins directory. Please contact your system administrator for more details.

Q: I'm having trouble installing the Java Plug-in Software on my Win32 machine. I see the error: "An application error has occurred and an application error log is being generated. Exception: access violation ..." What might be the problem? 

A: The Win32 installation (using Installshield's installer) may not work if you have Quarterdeck's Cleansweep product running in the background.

Q: When I reboot after I uninstalling Java Plug-in software, I get a dialog box warning that a .cplfile has been removed. What is this?

A: If the control panel is open while you are uninstalling the plug-in, plugincpl.cpl will not be removed as it is locked when the control panel folder is open.

Q: When I uninstall Java Plug-in Software, the Win32 plugin seems to stay in the machine. How can I remove that? 

A: Delete the NPJava32.dll from the Plugin directory.

Troubleshooting Security Issues   back to top  

Q: I have some security related issues in my applet. How do I debug it?

A: You can enable the /tt> property to enable trace messages from the security system. Please read the Java Plug-in online documentation for more information.

Q: When downloading applets from the Internet through Java Plug-in an AccessControlExcpetion is thrown. However, when the applet is located on the intranet, it works. Why?

A: To prevent DNS spoofing, a security check in Java Plug-in requires the host name to be resolved into an IP address, before any connection is made from the applet. However, the side-effect of this security check is to require the intranet DNS server to be able to resolve any external host name from the Internet. For some customers, this is not the way their DNS servers are setup within the enterprise, and it causes Java Plug-in to fail. To resolve this issue, there are several options:

  1. Modify the HTML page of the applet, so the codebase and document base of the applet contains IP addresses instead of host names. This will avoid Java Plug-in performing a DNS lookup for the host name.
  2. Set trustProxy to true in Java Plug-in. By setting this property, Java Plug-in will trust the proxy to perform a proper DNS lookup and return materials to Java Plug-in from trusted hosts. For intranet customers whose proxy servers are setup internally and can be trusted, this property may be used. This property may be specified as "-DtrustProxy=true" in the Java Plug-in Control Panel.

    Notice that this property should be set by administrator, as setting this property improperly with an untrusted proxy server may expose the client machines to DNS spoofing. This property is similar to the security.lower_java_network_security_by_trusting_proxies property supported by Netscape Navigator's JVM.

Q: I keep getting a ClassFormatError exception when my webpage that uses Java Plug-in Software 1.3 is loaded with HTTPS in Netscape Navigator. Why?

A: This is caused by an applet specifying a nonexistent .jar or .class file in the EMBED tag. Due to limitation of what information can be returned via HTTPS in Navigator, the web server's "File Not Found" HTML page is returned instead of the appropriate status. This HTML page is treated as a .class file which causes the exception.

Q: When my applet tries to make an HTTPS connection, it fails silently in IE, but a security dialog appears in Netscape. Why?

A: There are two problems:

  1. In HTTPS, a security certificate must be provided on the web server, so the browser will be able to verify if the machine can be trusted. If the security certificate has expired or if the certificate is used with the wrong machine (different host name), the browser will pop up a warning dialog and ask if the user wants to continue. You should verify that the security certificate is setup properly in HTTPS.
  2. In Java Plug-in, if there are problems with a security certificate in HTTPS, Netscape Navigator will by default pop up the warning dialog. However, in Internet Explorer, the warning dialog pop up only if URLConnection.setDefaultAllowUserInteraction() is set to true (the default is false). In the applet, if URLConnection.setDefaultAllowUserInteraction is set to true, you should see the warning dialog popup from IE.

Q: I tried to run an RSA signed applet with Java Plug-in, but it is being treated as an untrusted applet. What is the problem?

A: There are several possibilities:

  • Your applet is not signed properly. Please us the signtool to verify it.
  • Your RSA certificate and its certificate chain may have expired.

Q: Why does RSA signing not work in Internet Explorer 3.x?

A: RSA Applet signing is not supported in Internet Explorer 3.02 due to the limitation of the API implementation with this particular browser. In order to have the RSA signing technology work, the plugin is required to have the Crypto 2.0 API installed and to be able to open and use the Internet Explorer codestore to store, verify and retrieve certificates. Unfortunately, Internet Explorer 3.0x does not not provide access to its codestore through the Crypto 2.0 API.

Q. Why don't my signed applets work with Java Plug-in Software?

A: Signed applets using the Java 2 SDK, Standard Edition javakey mechanism are supported in Java Plug-in Software.

The most common problem is that the identitydb.obj file is not in the expected home directory. To check where Java Plug-in Software expects to find the user's home directory, you can use the Java Control Panel to enable the Java Console. Then when Java Plug-in Software starts up it will print out the user's home directory as the third line on the console.

Make sure that your identitydb.obj file is in that directory.

Q: In Java Plug-in Software 1.1. x, there was an option called "Network Access" in the Java Plug-in Software control panel. In Java Plug-in Software 1.3, this option seems to be disabled. Why?

A: Java Plug-in Software 1.3 comes with Java 2 SDK, Standard Edition/JRE 1.3, which does not support the "Network Access" option. To allow applets to connect to other hosts, use signed applets or change the policy file. See the Java 2 SDK, Standard Edition v 1.3 documentation for more information.

Q: Why do I get a yellow banner across my applet frame when using Java Plug-in Software?

A: When an applet creates a free-standing Frame, Java Plug-in Software adds a yellow warning banner so users will realize they are dealing with an untrusted applet window.

Q: Can I disable the yellow warning banner on frames? 

A: The yellow warning banner is an important security feature. It cannot be disabled by untrusted applets.

If you use a signed applet, where the signing key is trusted by the end user, then the warning banner will not be shown.

Q: How do I prevent the warning banner covering my GUI state? 

A: You should use the getInsets() method to find the size of your frame's decorative border. This includes the warning banner. For example, if you create a Frame with size 100x100, you might find it has insets [top=42,left=5,bottom=5,right=6] giving you a drawable area of 89x53. You need to position your work within the drawable area.

If you need to create a drawable area of a particular size, first create and show the Frame, then use getInsets to find the insets' sizes, then figure out the desired frame size by adding your desired size to the insets, then use frame.setSize() to set your frame to that size.

Q: Why does InetAddress.getLocalHost().getHostName() return "localhost"?

A: This is a deliberate security feature in the Java 2 platform. Untrusted applets will not be given the real host name.

Trusted applets (such as signed applets) will be given the real host name.

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