jsp中嵌入applet找不到类的问题解决
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下一篇 2012-04-19 00:34:32
/ 个人分类：jsp
背景：eclipse + tomcat +
webProject
问题：webProject首页中使用了applet嵌入，结果提示applet类无法查找
解决方案：在应用程序根目录下新建
applet 文件夹，将编译好的 applet.class 文件考到该文件夹下。
详细情况：
1、新建项目 MyApplet, index.jsp
源码：
- <%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
- <%
- String path = request.getContextPath();
- String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
- %>
-
- <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
- <html>
- <head>
- <base href="<%=basePath%>">
-
- <title>HelloWorld! Applet</title>
- <meta http-equiv="pragma" content="no-cache">
- <meta http-equiv="cache-control" content="no-cache">
- <meta http-equiv="expires" content="0">
- <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
- <meta http-equiv="description" content="This is my page">
-
-
-
- </head>
-
- <body>
- This is my JSP page. <br>
- <applet code="com.defonds.applet.HelloApplet.class" width=200 height=100 ></applet>
- </body>
- </html>
2、新建 applet 类 HelloApplet 源码：
- package com.defonds.applet;
-
- import java.applet.Applet;
- import java.awt.Graphics;
-
- public class HelloApplet extends Applet {
- public void paint(Graphics g) {
- g.drawString("Hello,Defonds!", 5, 35);
- }
- }
3、将 MyApplet 部署到 tomcat 容器下。启动 tomcat，访问
MyApplet。页面提示错误信息如下：
- 载入：找不到类 com.defonds.applet.HelloApplet.class。
- java.lang.ClassNotFoundException: com.defonds.applet.HelloApplet.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:9999/MyApplet/com/defonds/applet/HelloApplet/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: com.defonds.applet.HelloApplet.class
分析：applet 的 class 文件最好不要放在 web-inf 目录下，因为这是个特殊目录，所以http://localhost:9999/MyApplet/不能找到 com.defonds.applet.HelloApplet.class 这个文件。可以在 /webapps/MyApplet/
下新建一个文件夹，将 applet 的 class 文件放在里面，在重新设置 codebase 属性。
这样，新的目录结构如下：
测试用的
jsp /webapps/MyApplet/index.jsp
jsp 中插入的applet class
/webapps/MyApplet/applet/com/defonds/applet/HelloApplet.class
URL
http://localhost:9999/MyApplet/index.jsp
新的 index.jsp 源码如下：
- <%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
- <%
- String path = request.getContextPath();
- String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
- %>
-
- <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
- <html>
- <head>
- <base href="<%=basePath%>">
-
- <title>HelloWorld! Applet</title>
- <meta http-equiv="pragma" content="no-cache">
- <meta http-equiv="cache-control" content="no-cache">
- <meta http-equiv="expires" content="0">
- <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
- <meta http-equiv="description" content="This is my page">
-
-
-
- </head>
-
- <body>
- This is my JSP page. <br>
- <applet code="com.defonds.applet.HelloApplet.class" width=200 height=100 codebase="/MyApplet/applet/"></applet>
- </body>
- </html>
redeploy 一下 tomcat，重新访问 MyApplet 项目，发现 applet
已经成功嵌入。
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