JAVA APPLET读本地文件权限问题及解决办法一

http://hi.baidu.com/shiliangshuai/blog/item/3026134cecd46ffbd62afcd9.html

综合网络上的资料有2中方法：
1，使用数字签名。
2，修改策略文件。

这里使用的方法是修改策略文件：

首先要确定IE所使用的Jre安装在哪个目录下。但没有找到比较好的方法，一般默认是C:\Program Files\Java\下。从IE的Internet选项中可以看到目前使用的版本，那就进入C:\Program Files\Java\中对应版本的文件夹。本机是C:\Program Files\Java\j2re1.4.2_05\

然后，进入到.\lib\security下，打开java.policy文件。在grant的括号中填写
permission java.io.FilePermission "<<ALL FILES>>", "read,write";
本机修改的结果就是：

// Standard extensions get all permissions by default

grant codeBase "file:${java.home}/lib/ext/*" {
permission java.security.AllPermission;
};

// default permissions granted to all domains

grant {
// Allows any thread to stop itself using the java.lang.Thread.stop()
// method that takes no argument.
// Note that this permission is granted by default only to remain
// backwards compatible.
// It is strongly recommended that you either remove this permission
// from this policy file or further restrict it to code sources
// that you specify, because Thread.stop() is potentially unsafe.
// See " http://java.sun.com/notes " for more information.
permission java.lang.RuntimePermission "stopThread";

// allows anyone to listen on un-privileged ports
permission java.net.SocketPermission "localhost:1024-", "listen";

// "standard" properies that can be read by anyone

permission java.util.PropertyPermission "java.version", "read";
permission java.util.PropertyPermission "java.vendor", "read";
permission java.util.PropertyPermission "java.vendor.url", "read";
permission java.util.PropertyPermission "java.class.version", "read";
permission java.util.PropertyPermission "os.name", "read";
permission java.util.PropertyPermission "os.version", "read";
permission java.util.PropertyPermission "os.arch", "read";
permission java.util.PropertyPermission "file.separator", "read";
permission java.util.PropertyPermission "path.separator", "read";
permission java.util.PropertyPermission "line.separator", "read";

permission java.util.PropertyPermission "java.specification.version", "read";
permission java.util.PropertyPermission "java.specification.vendor", "read";
permission java.util.PropertyPermission "java.specification.name", "read";

permission java.util.PropertyPermission "java.vm.specification.version", "read";
permission java.util.PropertyPermission "java.vm.specification.vendor", "read";
permission java.util.PropertyPermission "java.vm.specification.name", "read";
permission java.util.PropertyPermission "java.vm.version", "read";
permission java.util.PropertyPermission "java.vm.vendor", "read";
permission java.util.PropertyPermission "java.vm.name", "read";
permission java.io.FilePermission "<<ALL FILES>>", "read,write";

};

这样就可以让applet读写本地文件了。

http://www.iteye.com/topic/334220

代码没有问题,是java.policy配置文件没配置好.修改配置文件就行.打开java.policy文件,在最后添加上如下代码就OK:
文件一般在下面目录下:jre/lib/security/java.policy
添加代码:
permission java.security.AllPermission;
permission java.net.SocketPermission "200.200.200.66:8000","accept,connect,listen,resolve";
就OK.因为applet有它设置的安全级别.如果你没有允许的话,就不允许你操作你电脑上的文件和其它东西.