Java applet 错误...出了什么问题？
Java小程序代码
package M257Applet
import java.applet.*;
import javax.swing.*;
import java.awt.*;
public class HellowApplet extends JApplet {
public void init(){
Container cp = getContentPane();
JLabel lb = new JLabel("Hellowwwww");
cp.add(lb);
}
}
html文件
<html>
<head>
<title>Applet</title>
</head>
<body>
<APPLET CODE = HellowApplet.class WIDTH = 400 HEIGHT = 400 >
</APPLET>
</body>
</html>
错误
Java Plug-in 1.6.0_22
Using JRE version 1.6.0_22-b04 Java HotSpot(TM) Client VM
User home directory = C:\Users\pc
----------------------------------------------------
c: clear console window
f: finalize objects on finalization queue
g: garbage collect
h: display this help message
l: dump classloader list
m: print memory usage
o: trigger logging
q: hide console
r: reload policy configuration
s: dump system and deployment properties
t: dump thread list
v: dump thread stack
x: clear classloader cache
0-5: set trace level to <n>
----------------------------------------------------
java.lang.NoClassDefFoundError: HellowApplet (wrong name: M257Applet/HellowApplet)
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 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$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Exception: java.lang.NoClassDefFoundError: HellowApplet (wrong name: M257Applet/HellowApplet)
Java applet code
package M257Applet
import java.applet.*;
import javax.swing.*;
import java.awt.*;
public class HellowApplet extends JApplet {
public void init(){
Container cp = getContentPane();
JLabel lb = new JLabel("Hellowwwww");
cp.add(lb);
}
}
html file
<html>
<head>
<title>Applet</title>
</head>
<body>
<APPLET CODE = HellowApplet.class WIDTH = 400 HEIGHT = 400 >
</APPLET>
</body>
</html>
Error
Java Plug-in 1.6.0_22
Using JRE version 1.6.0_22-b04 Java HotSpot(TM) Client VM
User home directory = C:\Users\pc
----------------------------------------------------
c: clear console window
f: finalize objects on finalization queue
g: garbage collect
h: display this help message
l: dump classloader list
m: print memory usage
o: trigger logging
q: hide console
r: reload policy configuration
s: dump system and deployment properties
t: dump thread list
v: dump thread stack
x: clear classloader cache
0-5: set trace level to <n>
----------------------------------------------------
java.lang.NoClassDefFoundError: HellowApplet (wrong name: M257Applet/HellowApplet)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Exception: java.lang.NoClassDefFoundError: HellowApplet (wrong name: M257Applet/HellowApplet)
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评论（2）
问题出在包裹上。您需要更改小程序的代码属性，并且根据您放置 HTML 的位置，还需要更改代码库属性。您必须将 HellowApplet.class 放在名为 M257Applet 的目录中（因为这是您提供的包），并且 applet 标记应如下所示：
为此，您的 HTML 必须与 M257Applet 位于同一目录中（而不是M257Applet 内）。或者，您可以指定代码库属性。例如，具有以下目录结构：
小程序将运行。但是，如果您有
，则必须像这样指定 codebase 属性：
因此，您应该让
codebase指向包含您的包的目录，并且code必须具有您的包名也在里面。编辑：
请注意，即使
code="HellowApplet.class"可以工作，指定小程序的正确方法是末尾不带“.class”。Problem is with the package. You need to change the code attribute of applet, and based on where you have placed your HTML, the codebase attribute too. You have to place HellowApplet.class in a directory called M257Applet (because that is the package you have given), and the applet tag should look something like:
For this to work, your HTML has to be in the same directory as M257Applet (not inside M257Applet). Alternatively, you can specify the codebase attribute. For eg, with the following directory structure:
the applet will work. If however, you had
then you will have to specify codebase attribute like so:
So, you should have
codebasepointing to the directory containing your package, andcodehas to have your package name also in it.Edit:
Please note, even though
code="HellowApplet.class"will work, the correct way of specifying the applet is without the ".class" at the end.您的课程在一个包中。它的文件名应该匹配。
（遵循约定是个好主意。包名称应该全部小写。）
Your class is in a package. It's file name should match.
(It's a good idea to follow conventions. Package names should be all lower case.)