How to embed a Java applet?

Question

I wrote a simple java applet in NetBeans and am having real trouble getting it embedded. I take my class file and copy that to the same directory as my html page. I also put my .jar there. On the html page I do

<applet code="ServerStatus.class" width="200" height="200">
Your browser does not support the <code>applet</code> tag.
</applet> 

But the applet never loads. The first bit of the long error is:

load: class ServerStatusChecker.jar not found.
java.lang.ClassNotFoundException: ServerStatusChecker.jar

What do I have to do to embed this applet? The top of my MyApplet.java file is

package org.me.serverstatuschecker;

import java.applet.*;
import java.awt.*; 
import java.awt.event.*;
import java.io.*;
import java.net.*;

public class MyApplet extends Applet implements ActionListener  {

My ServerStatusChecker.jar is in the same place as the html file im trying to include it in. Inside the jar i have folders org/me/serverstatuschecker/MyApplet.class.

EDIT:

The full error message is as follows:

 Java Plug-in 1.6.0_31
 Using JRE version 1.6.0_31-b05 Java HotSpot(TM) Client VM

 ----------------------------------------------------


    java.lang.UnsupportedClassVersionError: org/me/serverstatuschecker/ServerStatusChecker : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.defineClassHelper(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.access$100(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.plugin2.applet.Plugin2ClassLoader.findClassHelper(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
    Exception: java.lang.UnsupportedClassVersionError: org/me/serverstatuschecker/ServerStatusChecker : Unsupported major.minor version 51.0
    java.lang.UnsupportedClassVersionError: org/me/serverstatuschecker/ServerStatusChecker : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.defineClassHelper(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.access$100(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.plugin2.applet.Plugin2ClassLoader.findClassHelper(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
    Exception: java.lang.UnsupportedClassVersionError: org/me/serverstatuschecker/ServerStatusChecker : Unsupported major.minor version 51.0
    java.lang.UnsupportedClassVersionError: org/me/serverstatuschecker/ServerStatusChecker : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.defineClassHelper(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.access$100(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.plugin2.applet.Plugin2ClassLoader.findClassHelper(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
    Exception: java.lang.UnsupportedClassVersionError:      org/me/serverstatuschecker/ServerStatusChecker : Unsupported major.minor version 51.0
    java.lang.UnsupportedClassVersionError: org/me/serverstatuschecker/ServerStatusChecker :   Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.defineClassHelper(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.access$100(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.plugin2.applet.Plugin2ClassLoader.findClassHelper(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
    Exception: java.lang.UnsupportedClassVersionError:          org/me/serverstatuschecker/ServerStatusChecker : Unsupported major.minor version 51.0

Answer 1

Directory Structure

• theappletdir/
  • applet.html
  • ServerStatusChecker.jar

Content of applet.html

Then use the script supplied by Oracle to deploy applets and JWS apps. It is called deployJava.js and linked from the applet info. page. It will:

• Check the minimum stated JRE version is available for use by applets.
  • If not, help the user to upgrade it.
• Embed & run the applet.

---

<html>
<head>
<!-- ... -->
<script src="http://www.java.com/js/deployJava.js"></script>
</head>
<body>
<!-- ... -->
<script>
    var attributes = {codebase:'.',
                      code:'org.me.serverstatuschecker.MyApplet',
                      archive:'ServerStatusChecker.jar',
                      width:200, height:200};
    var parameters = {};
    var version = '1.6';  // or whatever version the code was compiled for 
    deployJava.runApplet(attributes, parameters, version);
</script>
</body>
</html>

New Error

UnsupportedClassVersionError: org/me/serverstatuschecker/MyApplet : 
    Unsupported major.minor version 51.0

When I refer to the version number list it indicates the code is being compiled compatible for a 1.7 JRE, whereas the version attribute above indicates the code should be able to be loaded in any 1.6+ JRE. The best way to fix this is to use the source, target bootclasspath options when compiling the code. Specify the first 2 as 1.6 and the last as a path to a 1.6 version rt.jar.

Answer 2

Have you tried the HtmlConverter Tool?

http://java.sun.com/products/plugin/1.3/docs/htmlconv.html

It creates a HTML code that tries to load your applet properly with the Java Plugin.