java - 如何嵌入Java小程序？

Question

我在 NetBeans 中编写了一个简单的 Java 小程序，但在嵌入它时遇到了很大的麻烦。我将类文件复制到与 html 页面相同的目录中。我也把我的 .jar 放在那里。在 html 页面上我这样做

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

但是小程序永远不会加载。长错误的第一位是:

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

我需要做什么才能嵌入这个小程序？我的 MyApplet.java 文件的顶部是

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  {

我的 ServerStatusChecker.jar 与我试图将其包含在内的 html 文件位于同一位置。在 jar 内，我有文件夹 org/me/serverstatuschecker/MyApplet.class。

编辑:

完整的错误消息如下:

 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

目录结构

• theappletdir/
  • applet.html
  • ServerStatusChecker.jar

applet.html的内容

然后使用 Oracle 提供的脚本来部署 applet 和 JWS 应用程序。它称为 deployJava.js 并从 applet info. page 链接。 。它将:

• 检查规定的最低 JRE 版本是否可供小程序使用。
  • 如果没有，请帮助用户升级。
• 嵌入并运行小程序。

<小时/>

<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>

新错误

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

当我引用version number list时它指示代码正在编译为与 1.7 JRE 兼容，而上面的 version 属性指示代码应该能够在任何 1.6+ JRE 中加载。解决此问题的最佳方法是在编译代码时使用 source、target bootclasspath 选项。将前 2 个指定为 1.6，最后一个指定为 1.6 版本 rt.jar 的路径。