Chapter 2

Using the Conventional Applet Tag

Support for the APPLET Tag

Java Plug-in now supports the HTML APPLET tag for launching applets. Users may configure their browsers so that JRE 1.4.0 is the default runtime environment for handling APPLET tags.

For developers, the Java Plug-in enhancements enable you to deploy your applet web pages without the need for an HTML Converter or the use of OBJECT tags, while still being able to ensure that your users will have the latest JRE/Java Plug-in for running your code.

Even though Java Plug-in now supports the APPLET tag, it does not support applets that make use of proprietary technologies. Examples of such technologies are

CAB files
Authenticode signing
Java Moniker

Compatibility with the OBJECT Tag

This release of Java Plug-in supports the use of APPLET tags for launching applets. However, it is also fully backward compatible with previous Java Plug-in releases in its support of the OBJECT tag for launching applets. Developers have the option of using the HTML Converter to set up their applet web pages to use the OBJECT tag as before.

Supported Browsers

Java Plug-in provides support for the APPLET tag on the following web browsers:

Internet Explorer 4.0 (4.01 recommended), 5.0 (5.01 recommended), 5.5 (Service Pack 2 recommended), 6.0
Netscape 6.0, 6.1

Updating Old Class Files

In some cases, the new Java Runtime Environment associated with this Java Plug-in release will not run class files that were generated with old compilers. The usual symptom is a java.lang.ClassFormatError that the virtual machine throws when it attempts to load such a class file. This failure has nothing specifically to do with the changes in this release. Rather, old bytecode compilers did not strictly adhere to proper class-file format in all situations when generating class files. Recent virtual machines are implemented to be strict in enforcing proper class file format, and this can lead to errors when they attempt to load old, improperly formatted class files. Some typical problems in some older class files are (this list is not exhaustive):

There are extra bytes at the end of the class file;
The class file contains method or field names that do not begin with a letter;
The class attempts to access private members of another class;
The class file has other format errors, including illegal constant pool indices and illegal UTF-8 strings;
Some early (third-party) bytecode obfuscators produced class files that violated proper class-file format.

You can avoid this type of problem by recompiling your classes with the Javac bytecode compiler from the current Java 2 SDK. If you choose to use a third-party obfuscator, be sure to use one that produces class files that respect proper class-file format.


	Chapter 2 Using the Conventional Applet Tag Support for the APPLET Tag Java Plug-in now supports the HTML APPLET tag for launching applets. Users may configure their browsers so that JRE 1.4.0 is the default runtime environment for handling APPLET tags. For developers, the Java Plug-in enhancements enable you to deploy your applet web pages without the need for an HTML Converter or the use of OBJECT tags, while still being able to ensure that your users will have the latest JRE/Java Plug-in for running your code. Even though Java Plug-in now supports the APPLET tag, it does not support applets that make use of proprietary technologies. Examples of such technologies are CAB files Authenticode signing Java Moniker Compatibility with the OBJECT Tag This release of Java Plug-in supports the use of APPLET tags for launching applets. However, it is also fully backward compatible with previous Java Plug-in releases in its support of the OBJECT tag for launching applets. Developers have the option of using the HTML Converter to set up their applet web pages to use the OBJECT tag as before. Supported Browsers Java Plug-in provides support for the APPLET tag on the following web browsers: Internet Explorer 4.0 (4.01 recommended), 5.0 (5.01 recommended), 5.5 (Service Pack 2 recommended), 6.0 Netscape 6.0, 6.1 Updating Old Class Files In some cases, the new Java Runtime Environment associated with this Java Plug-in release will not run class files that were generated with old compilers. The usual symptom is a `java.lang.ClassFormatError` that the virtual machine throws when it attempts to load such a class file. This failure has nothing specifically to do with the changes in this release. Rather, old bytecode compilers did not strictly adhere to proper class-file format in all situations when generating class files. Recent virtual machines are implemented to be strict in enforcing proper class file format, and this can lead to errors when they attempt to load old, improperly formatted class files. Some typical problems in some older class files are (this list is not exhaustive): There are extra bytes at the end of the class file; The class file contains method or field names that do not begin with a letter; The class attempts to access private members of another class; The class file has other format errors, including illegal constant pool indices and illegal UTF-8 strings; Some early (third-party) bytecode obfuscators produced class files that violated proper class-file format. You can avoid this type of problem by recompiling your classes with the Javac bytecode compiler from the current Java 2 SDK. If you choose to use a third-party obfuscator, be sure to use one that produces class files that respect proper class-file format.