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calling a dll from an applet via jni using -'java,applet,jni'


calling a dll from an applet via jni  using -'java,applet,jni'

I have a "proof of concept" piece of work that crosses over into some unfamiliar territory.
I'm tasked with connecting an EFTPOS machine to an application running as an applet in a browser on our intranet.

I've ignored the EFTPOS dll for the moment and created a simple JNI decorated DLL in my language of choice (Delphi) that just logs a string to a text file in c:\ and I can call it successfully from a local Java application.

However, when I create an applet to do the same thing, compile it into a .JAR, sign the JAR & try to call the method in the applet via Javascript on a web page it fails.

A senior Java guy I'm working with doesn't think it will be possible to get this to work because it's inherently "evil" to allow an applet to do this.

There is an entry you can put in a java.policy file to allow loadLibrary. as well as allPermission & I've tried a whole host of variations along those lines all to no avail producing the following error trace in the Java Console:

java.lang.ExceptionInInitializerError
  at app.TestApplet.LogAString(Unknown Source)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  at java.lang.reflect.Method.invoke(Unknown Source)
  at sun.plugin.javascript.JSInvoke.invoke(Unknown Source)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  at java.lang.reflect.Method.invoke(Unknown Source)
  at sun.plugin.javascript.JSClassLoader.invoke(Unknown Source)
  at sun.plugin.com.MethodDispatcher.invoke(Unknown Source)
  at sun.plugin.com.DispatchImpl.invokeImpl(Unknown Source)
  at sun.plugin.com.DispatchImpl$1.run(Unknown Source)
  at java.security.AccessController.doPrivileged(Native Method)
  at sun.plugin.com.DispatchImpl.invoke(Unknown Source)
Caused by: java.security.AccessControlException: access denied (java.lang.RuntimePermission loadLibrary.DLoggerImpl)
  at java.security.AccessControlContext.checkPermission(Unknown Source)
  at java.security.AccessController.checkPermission(Unknown Source)
  at java.lang.SecurityManager.checkPermission(Unknown Source)
  at java.lang.SecurityManager.checkLink(Unknown Source)
  at java.lang.Runtime.loadLibrary0(Unknown Source)
  at java.lang.System.loadLibrary(Unknown Source)
  at app.DLogger.<clinit>(Unknown Source)
  ... 16 more
java.lang.Exception: java.lang.ExceptionInInitializerError
  at sun.plugin.com.DispatchImpl.invokeImpl(Unknown Source)
  at sun.plugin.com.DispatchImpl$1.run(Unknown Source)
  at java.security.AccessController.doPrivileged(Native Method)
  at sun.plugin.com.DispatchImpl.invoke(Unknown Source)


The key line seems to be "Caused by: java.security.AccessControlException: access denied (java.lang.RuntimePermission loadLibrary.DLoggerImpl)" which implies a permissions problem.  It could be that I'm getting the policy file wrong - or the signing wrong - or stuff like that or it could be that Java is hardwired to not allow those sort of permissions for an Applet because of the security risk.

My question is am I wasting my time?  Can it be done & if so, how?

Thanks in anticipation

Mike
    

asked Sep 7, 2015 by rajesh
0 votes
9 views



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