在线等待：jsp编程中遇到java.lang.ClassNotFoundException:

答案:4 悬赏:40

解决时间 2021-12-13 11:26

提问者网友：喵星人荷西
2021-12-13 03:26

首先是showmsg.java文件：
import java.awt.*;
import java.applet.*;
pulic class showmsg extends Applet
{
String msg1,msg2,msg3;
public void init()
{
msg1=getParameter("msg1");
msg2=getParameter("msg2");
msg3=getParameter("msg3");
}
public void paint(Graphics g)
{
Font font = new Font("SanSerif",Font.BOLD,30);
g.getFont(font);
g.setColor(Color.blue);
g.drawString(msg1,20,40);
g.drawString(msg2,20,70);
g.drawString(msg3,20,100);
}
}
然后是usingPlugin.jsp文件
<%@page contentType="text/html" %>
<%@page pageEncoding="GB2312" import="java.awt.*,java.applet.*" %>
<html>
<head>
<title>演示 plugin</title>
</head>
<body>
<jsp:plugin type="applet" code="showmsg.class" height="200" width="200">
<jsp:params>
<jsp:param name="msg1" value="C++" />
<jsp:param name="msg2" value="Java" />
<jsp:param name="msg3" value="C#" />
</jsp:params>
</jsp:plugin>
</body>
</html>
在IE里输入http://localhost:8080/usingPlugin.jsp后，错误，原因如下：
载入：找不到类 showmsg.class。
java.lang.ClassNotFoundException: showmsg.class
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.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.io.IOException: open HTTP connection failed:http://localhost:8080/showmsg/class.class
at sun.plugin2.applet.Applet2ClassLoader.getBytes(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.access$000(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
... 7 more
异常：java.lang.ClassNotFoundException: showmsg.class
载入：找不到类 showmsg.class。
java.lang.ClassNotFoundException: showmsg.class
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.io.IOException: open HTTP connection failed:http://localhost:8080/showmsg/class.class
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)
... 7 more
异常：java.lang.ClassNotFoundException: showmsg.class
请大家指教

最佳答案

二级知识专家网友：随心随缘不随便
2021-12-13 04:50

看一下showmsg.java这个类大小写
import java.awt.*;
import java.applet.*;
public class showmsg extends Applet
{
String msg1,msg2,msg3;
public void init()
{
msg1=getParameter("msg1");
msg2=getParameter("msg2");
msg3=getParameter("msg3");
}
public void paint(Graphics g)
{
Font font = new Font("SanSerif",Font.BOLD,30);
g.setFont(font);
g.setColor(Color.blue);
g.drawString(msg1,20,40);
g.drawString(msg2,20,70);
g.drawString(msg3,20,100);
}
}
这个类你仔细看看写错了两个地方 public 和 setFont()
然后javac一下把class文件和jsp放到root下就OK了

全部回答

1楼网友：转身后的回眸
2021-12-13 07:50

看一下showmsg.java这个类大小写 import java.awt.*; import java.applet.*; public class showmsg extends applet { string msg1,msg2,msg3; public void init() { msg1=getparameter("msg1"); msg2=getparameter("msg2"); msg3=getparameter("msg3"); } public void paint(graphics g) { font font = new font("sanserif",font.bold,30); g.setfont(font); g.setcolor(color.blue); g.drawstring(msg1,20,40); g.drawstring(msg2,20,70); g.drawstring(msg3,20,100); } } 这个类你仔细看看写错了两个地方 public 和 setfont() 然后javac一下把class文件和jsp放到root下就ok了cindyzhangl考虑采纳一下。有空到365testing,测评网,

2楼网友：甜野猫
2021-12-13 06:53

查检一个类名，这个异常说的是地，没有发现类异常：没有发现showmsg.class 你看看有没有这个类。

3楼网友：迷人小乖乖
2021-12-13 05:16

code="showmsg.class" 这里检查下你的jsp和class文件是否放在一个目录下。注意是编译后的class文件，不是java源文件。如果是有用eclipse，你可以直接在类里面右键选择Run as Applet来调试程序。

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