用数字签名的applet解决客户端文件读写

rautinee

浏览: 96213 次
来自: 成都四川

最近访客更多访客>>

u012363178

wangyy

bigbirdzk

itshu

博主相关

博客

微博

相册

留言

关于我

文章分类

社区版块

存档分类

JavaScript 编程 Yahoo F#Flash

最近有个java的B/S项目，要求能在客户端读写文件，查了下资料，解决方案一般是写activex和applet，由于项目是跨浏览器的，所以activex不能满足要求，out了，只能用applet，要解决applet在客户端读写的问题，需要给applet数字签名，最后经过几番尝试，终于调试通过，现发出来给大家共享。

首先写applet了

package com.shiningway.applet;

import java.applet.Applet;
import java.io.*;
import java.awt.*;
import java.util.*;
public class ShowMe extends Applet{
	public File f=null;
	public String text="";//请注意此处的public   
	Date dd=null;
	int n=0;


	/**
	 * Called by the browser or applet viewer to inform
	 * this applet that it is being reclaimed and that it should destroy
	 * any resources that it has allocated. The <code>stop</code> method
	 * will always be called before <code>destroy</code>. <p>
	 *
	 * A subclass of <code>Applet</code> should override this method if
	 * it has any operation that it wants to perform before it is
	 * destroyed. For example, an applet with threads would use the
	 * <code>init</code> method to create the threads and the
	 * <code>destroy</code> method to kill them. <p>
	 */
	public void destroy() {
		// Put your code here
	}

	 public void paint(Graphics g ) {
		 if(text!=null && !text.equals(""))
		 {
			 setTxt(text);
		 }
		 //g.drawString(text, 40, 50);
		 text="";
    }
	 
	 public void setText(String st)
	 {
		 
		 text=st;
	 }



	public void init() {
		f=new File("D:\\lala.txt");
		if (!f.exists())
		{
			try
			{
				f.createNewFile();
			}
			catch(Exception ex)
			{
				System.out.println(ex.getMessage());
			}
			
		}
		
	}
	
	public void setTxt(String tt)
	{
		
	
			try
			{
				RandomAccessFile raf = new RandomAccessFile(f, "rw"); 
				raf.seek(raf.length());
				raf.writeBytes("\n"+tt);
				raf.close();
			}
			catch (Exception ex)
			{
				System.out.println(ex.getMessage());
			}
			finally
			{
			
			}
			
			
		
	}

	public void start() {
	
	}

	/**
	 * Called by the browser or applet viewer to inform
	 * this applet that it should stop its execution. It is called when
	 * the Web page that contains this applet has been replaced by
	 * another page, and also just before the applet is to be destroyed. <p>
	 *
	 * A subclass of <code>Applet</code> should override this method if
	 * it has any operation that it wants to perform each time the Web
	 * page containing it is no longer visible. For example, an applet
	 * with animation might want to use the <code>start</code> method to
	 * resume animation, and the <code>stop</code> method to suspend the
	 * animation. <p>
	 */
	public void stop() {
		// Put your code here
	}

}

关于applet的数字签名，网上资料很多，自己可以去查，可以参考一下这个帖子http://www.blogjava.net/beansoft/archive/2008/05/11/199801.html
（其实这个帖子里面已经是包含了我这边的大部分内容了）
showMe.html的文件代码
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <title>My applet 'ShowMe' starting page</title>

    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="this is my page">
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">

</head>
<script>
function setTxt()
{
document.lama.setText(document.getElementById("txtbaby").value);
document.lama.repaint();
}
</script>
<body>


<object
    classid = "clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
    codebase = "http://java.sun.com/update/1.5.0/jinstall-1_5-windows-i586.cab#Version=1,5,0,0"
    WIDTH = "300" HEIGHT = "400" NAME = "lama" >
    <PARAM NAME = CODE VALUE = "com.shiningway.applet.ShowMe.class" >
    <PARAM NAME = ARCHIVE VALUE = "test.jar" >
    <PARAM NAME = NAME VALUE = "lama" >
    <PARAM NAME = MAYSCRIPT VALUE = true >
    <param name = "type" value = "application/x-java-applet;version=1.5">
    <param name = "scriptable" value = "false">

    <comment>
<embed
            type = "application/x-java-applet;version=1.5" \
            CODE = "com.shiningway.applet.ShowMe.class" \
            ARCHIVE = "test.jar" \
            NAME = "lama" \
            WIDTH = "300" \
            HEIGHT = "400" \
            MAYSCRIPT = true
    scriptable = false
    pluginspage = "http://java.sun.com/products/plugin/index.html#download">
    <noembed>

            </noembed>
</embed>
    </comment>
</object>




<input type="text" name="txtbaby" id="txtbaby">
<input type="button" onclick="setTxt()" value="添加内容">
</body>
</html>

这个例子的效果是在showMe.html中的输入框中输入内容，然后点击添加内容按钮，改内容回自动保存在客户端D盘的lala.txt文件中
总结一下，知识点主要是以下几点

applet编程
applet数字签名
java文本文件的读写操作
javascript如何与applet通信

疑问：
网页中javascript不能直接调用applet中文件读写的方法setTxt，查看java控制台信息提示无权限，即使用了签名也是如此，后来只有写在paint方法里面，在javascript中用repaint来调用。有没有遇到这个问题的，你们是如何解决的，欢迎来信讨论,email：rautinee@yahoo.com.cn

applet客户端读写.rar (4.9 KB)
下载次数: 196

分享到：

户外知识教程：教大家如何用炉头转接头 | 沉默了很久，要重新更新我的博客了！

2010-01-24 13:21
浏览 2224
评论(4)
论坛回复 / 浏览 (3 / 3901)
分类:编程语言
查看更多

4 楼 jiao_zg22 2012-04-17

遇到相同问题，我用JavaScript读取文件，获得的值传到applet中作为二进制数组获取时报错，也就是二进制数组无法从js传到applet里面，能否解决这个问题？

3 楼 fyland 2010-05-24

现在很少有人用applet
一般都是用flash，98%的装机率，无可比拟的优势

2 楼 ivy013 2010-05-24

rautinee 写道

//在你的Showme类中加入下面的代码就ok了，
static {
		System.setSecurityManager(null);
	}

1 楼 cuixiping 2010-01-26

我也借鉴一下。
暂时还没遇到这种需求。
一般我都弄成导入导出的功能，让用户上传和保存有关文件。

发表评论

您还没有登录,请您登录后再发表评论

最近访客更多访客>>

博主相关

文章分类

社区版块

存档分类

最新评论