小程序。 java.lang.reflect.InvocationTargetException

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我有小程序使用JNA指针类。小程序code是：

进口com.sun.jna *。公共类Applet1扩展的Applet { 公共无效测试（）{ 尝试{ 指针p =新的内存（73）; }赶上（例外五）{ e.printStackTrace（）; } }}

在HTML code我宣布小程序是这样的：

＆LT;小程序 codeBase的= / PKI / code = Applet1.class 存档= / PKI / JNA-3.2.3.jar ID = Applet1 宽度= 100 高度= 100〕＆LT; /小程序＆GT;

当我打电话的document.getElementById（Applet1）。试验（+）由JavaScript的java.lang.reflect.InvocationTargetException出现。我不能叫e.getCause（）将Java类方面，由于小应用程序的try / catch不捕获的错误（我不明白为什么）。但JavaScript的try / catch语句捕获此错误。如果移动指针p =新的内存（73）; 行这将是确定。这个问题是此行。请帮助解决这个问题。

编辑：如果更换此块：

{尝试指针p =新的内存（73）;}赶上（例外五）{ e.printStackTrace（）;}

到

{尝试指针p =新的内存（73）;}赶上（Throwable的E）{ 的System.out.println（e.getCause（））;}

我java.security.AccessControlException：访问被拒绝（java.util.PropertyPermission jna.boot.library.path读）

解决方案

好了，现在我们来到了问题的根源。（您仍然可以使用了的printStackTrace - 这应该已打印的堆栈跟踪事业，也。）

未签名的Applet只有系统属性数量有限的访问 - 在 JNA 属性不是这些部分

在一个未签名的Applet无法加载本地库反正，所以没有办法用JNA（或JNI，顺便说一句）。

如果您签名Applet（并告诉插件接受签名），您的小程序必须使用JNA的必要权限。但是，任何单个运行code的权利是有效的，要求当前code所有方法的权限的交集。

Applet的方法从JavaScript叫有极其有限的权限（因为插件不能真正检查的JavaScript code具有必要的权限，如果你的浏览器，甚至有这样一个概念）。

您可以去解决这个通过包装code，它需要与你的小程序的权限运行，以在AccessController.doPrivileged（...）部分。但首先确保这个不能做任何危险的（这是很容易用JNI / JNA），由恶意的JavaScript code叫时也是如此。

I have applet which use jna Pointer class. The applet code is:

import com.sun.jna.*; public class Applet1 extends Applet{ public void test() { try { Pointer p = new Memory(73); } catch (Exception e) { e.printStackTrace(); } } }

In html code I declared applet this way:

When i call document.getElementById("Applet1").test() by javascript the java.lang.reflect.InvocationTargetException arise. I cant call e.getCause() in the java class side, because applet try/catch dont catch the error (I dont understand why). But javascript try/catch catch this error. If move Pointer p = new Memory(73); line it will be ok. The matter is this line. Please, help to fix the problem.

EDIT: if replace this block:

try { Pointer p = new Memory(73); } catch (Exception e) { e.printStackTrace(); }

try { Pointer p = new Memory(73); } catch (Throwable e) { System.out.println(e.getCause()); }

I got java.security.AccessControlException: access denied (java.util.PropertyPermission jna.boot.library.path read)

解决方案

Okay, now we come to the root of the problem. (You still could have used printStackTrace - this should have printed the stack trace of the cause, too.).

Unsigned applets have only access to a limited number of system properties - the jna properties are not part of these.

In an unsigned applet you can't load native libraries anyways, so no way to use JNA (or JNI, by the way).

If you sign the applet (and tell the plugin to accept the signature), your applet has the necessary rights to use JNA. But the rights of any single running code is effectively the intersection of the rights of all methods which called the current code.

Applet methods called from JavaScript have extremely limited permissions (since the Plugin can't really check that the JavaScript code has the necessary permissions, if your browser even has such a concept).

You can go around this by wrapping the part of the code, which needs to run with your applet's permissions, with AccessController.doPrivileged(...). But first make sure this can't do anything dangerous (which is easy with JNI/JNA), even when called from malicious JavaScript code.

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小程序。 java.lang.reflect.InvocationTargetException

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