Java SE (Java Platform, Standard Edition)

I found a similar problem with applets compiled with J2SDK1.4.1, when trying to load it with IE 5.5 or 6.0 without the java plugin, always I got a "Class not found error" on the myApplet class.

I think the class produced by JDK 1.4.0 are not compatible with the MS VM.

Ok, so there's been a lot of discussion in this forum around incompatibility between jdk 1.4x and applets running in IE.

The standard solution is to deploy a new plug-in. Is there an automatic way of request the user to download the plug-in if they don't already have it?

There is a way to make an automatic request like that. Before I tell you that though, you should try the following:

Since the IE 5 & 6 use the 1.1 plugin only, you should attempt to compile your program with:

javac -target1.1 yourApplet.java

Then load it in IE. If it works, then good. If it does not, you can use an <object> tag like so:

<object classid="clsid:CAFEEFAC-0014-0000-0000-ABCDEFFEDCBA" width=100 height=100 codebase="http://java.sun.com/products/plugin/autodl/jinstall-1_4_0-win.cab#Version=1,4,0,0"><param name="code" value="HelloWorld.class"><param name="archive" value="HelloWorld.jar"><param name="type" value="application/x-java-applet;jpi-version=1.4"><param name="scriptable" value="false"><comment><embed type="application/x-java-applet;jpi-version=1.4" archive="HelloWorld.jar" code="HelloWorld.class" width=100 height=100 scriptable=false pluginspage="http://java.sun.com/products/plugin/index.html#download"></embed></comment></object>

Any person with HTML logic can figure out where to put there class names in there etc. Here's what that does: it attempts to load the 1.4 plugin, if it is not installed, the user will be asked to download the plugin. Since the plugin is 30MB, you can imagine not many people who visit your site are going to wait that long (seeing as 70% of net surfers are on 56K). So before trying the object tag, try compiling with the 1.1 target so you're viewers won't have to download another plugin.

- Cut - Ehm, the plugin is 9MB...(see http://java.sun.com/products/plugin/index-1.4.1.html). 30MB is the all J2SDK

The clsid:CAFEEFAC-0014-0000-0000-ABCDEFFEDCBA is valid only if JRE1.1 is installed on client's mashine.
The valid CLSID is 8AD9C840-044E-11D1-B3E9-00805F499D93 (for version 1.4.0 and 1.4.1!).

Compiling with target=1.1 is partial solution, because java compiler do not report warnings if you use new methods of the old classes. For example java.awt.Font.class has method deriveFont(AffineTransform trans), which is defined in version 1.2. If I start to look every class which I use in my applet for compatibility with version 1.1 where is the reason to use newer version of the JDK ?!?

I continue to think that this is a serious mistake in compatibility mode of JDKs.

Anyway - thanks a lot for the replys! They are very usefull for me.

I had the same problem many times. I believe that APPLET is one of the most crucial component of Sun's Java to attract new programmers to our side of the competition battle. C# has already took our many java gurus with years of java experience to their side. I think Sun should pay more attention to applets, clarify and resolve many issues in favor of Java's future investment in market share.