load: class MyApplet not found : java.lang.ClassNotFoundException. Why am i getting this,when the class file is there in the package?

问题

I get the following exception when i try to run the applet :

load: class MyApplet not found.
java.lang.ClassNotFoundException: MyApplet
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)
Caused by: java.net.SocketTimeoutException: Read timed out
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at java.io.BufferedInputStream.fill(Unknown Source)
at java.io.BufferedInputStream.read1(Unknown Source)
at java.io.BufferedInputStream.read(Unknown Source)
at sun.net.www.http.HttpClient.parseHTTPHeader(Unknown Source)
at sun.net.www.http.HttpClient.parseHTTP(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.HttpURLConnection.getResponseCode(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.getBytes(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.access$000(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
... 9 more
Exception: java.lang.ClassNotFoundException: MyApplet

applet code :

import javax.swing.*;
import java.awt.*;

public class MyApplet extends JApplet {

public JFrame frame;
public JPanel panel;
public JButton button;

public void init() {
    frame = new JFrame();
    panel = new JPanel();
    button = new JButton("click me ");
    panel.setBackground(Color.RED);
    panel.add(button);
    frame.add(panel);
    frame.setSize(300,300);
    frame.setVisible(true);
}   
}

html code :

<applet code="MyApplet" codebase="AppletPackage" archive="JAR.jar" height="800" width="800">

JAR.jar file contains a package Appletpackage and this package contains a class file named MyApplet.class

Why do i get this exception ? Whare have i made the mistake ?

回答1:

The archive parameter is resolved relative to the codebase parameter. So in your case the plugin will look for a file MyApplet.class included in a file AppletPackage/JAR.jar.

You should change this to the following:

<applet code="AppletPackage.MyApplet" archive="JAR.jar" height="800" width="800">

This will resolve to AppletPackage/MyApplet.class inside JAR.jar in the same directory as the HTML file.

回答2:

This is an attempt to address the error message reported in a comment to my first answer:

java.lang.NoClassDefFoundError: AppletPackage/MyApplet (wrong name: MyApplet)

Looking at the sources, I see that this “wrong name” error message is an indication of a mismatch between file name and class name. You claim that your class is inside AppletPackage, and the file name AppletPackage/MyApplet.class fits that. But the source code you quoted above didn't contain a line

package AppletPackage;

You should add that line, so that the class file contains the fully qualified name of the class. Then you should be able to load it.

来源：https://stackoverflow.com/questions/11396646/load-class-myapplet-not-found-java-lang-classnotfoundexception-why-am-i-gett

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java

html

jar

applet

classnotfoundexception