I have a web app that needs to be able open a file locally on a client machine, with the ability to save the file after editing. The web app generates a document on the server in a folder that is shared out via WebDAV & FTP and this folder is mounted on the client machine.
I cannot use a file:// type URI as it would not permit saving back to the server.
I intend trying to solve the problem with a small java applet embedded in the web app that handles this file opening, but I am having difficulties with permissions in Java. (Java isn’t my field of expertise). Anyhow, I’ve narrowed the code down to the following:
localfile.html
<html>
<body>
<input id="input" value="Call from Javascript" type="button" onclick="callApplet('/Users/conor/1.txt')">
<script type='text/javascript'>
function callApplet(path) {
applet = document.getElementById('localfile');
applet.openFile(path);
}
</script>
<applet id="localfile" code="localfile.class" archive="localfile.jar" width="150" height="50"></applet>
</body>
</html>
localfile.java
import java.applet.*;
import java.awt.*;
import java.util.*;
import java.lang.*;
import java.text.*;
import java.awt.event.*;
import java.io.*;
import java.security.*;
public class localfile extends Applet {
public localfile() {
Panel p = new Panel();
p.add(new Button("Call from Java"));
add("North",p);
}
public void openFile(String path) {
System.out.println("File: " + path);
final File ffile = new File(path);
System.out.println("Got file.");
if (Desktop.isDesktopSupported()) {
System.out.println("Desktop is supported.");
final Desktop desktop = Desktop.getDesktop();
System.out.println("Got Desktop Handle.");
try {
desktop.open(ffile);
} catch(Exception ex) {
ex.printStackTrace();
}
System.out.println("File Opened.");
}
}
public boolean action(Event evt, Object arg) {
openFile("/Users/conor/1.txt");
return true;
}
}
I have compiled, created a jar file and signed it from the java source.
This produces a page with two buttons – a Java one (for testing) and a Javascript one. The Java button works fine as expected – and I can save the file etc. I want to pass the file path to the applet though so it is really the Javascript button I wish to get working. The Javascript one throws the following though:
Stack Trace
java.security.AccessControlException: access denied ("java.awt.AWTPermission" "showWindowWithoutWarningBanner")
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:366)
at java.security.AccessController.checkPermission(AccessController.java:560)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
at java.awt.Desktop.checkAWTPermission(Desktop.java:239)
at java.awt.Desktop.open(Desktop.java:267)
at localfile.openFile(localfile.java:27)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at sun.plugin.javascript.JSInvoke.invoke(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at sun.plugin.javascript.JSClassLoader.invoke(Unknown Source)
at sun.plugin2.liveconnect.JavaClass$MethodInfo.invoke(Unknown Source)
at sun.plugin2.liveconnect.JavaClass$MemberBundle.invoke(Unknown Source)
at sun.plugin2.liveconnect.JavaClass.invoke0(Unknown Source)
at sun.plugin2.liveconnect.JavaClass.invoke(Unknown Source)
at sun.plugin2.main.client.LiveConnectSupport$PerAppletInfo$DefaultInvocationDelegate.invoke(Unknown Source)
at sun.plugin2.main.client.LiveConnectSupport$PerAppletInfo$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.plugin2.main.client.LiveConnectSupport$PerAppletInfo.doObjectOp(Unknown Source)
at sun.plugin2.main.client.LiveConnectSupport$PerAppletInfo$LiveConnectWorker.run(Unknown Source)
at java.lang.Thread.run(Thread.java:722)
I have also tried embedding the desktop.open call into a doPrivileged block, as follows:
AccessController.doPrivileged(new PrivilegedAction() {
public Object run() {
try {
desktop.open(ffile);
} catch(Exception ex) {
ex.printStackTrace();
}
return null;
}
});
but that throws error for javascript & java buttons as follows:
java.lang.SecurityException: class "localfile$1" does not match trust level of other classes in the same package
Any help would be appreciated.
Got it to work, so thought I’d post the solution here…
When I was compiling the java file with the doPrivileged call in it, the javac compiler creates two files – localfile.class and localfile$1.class. I wasn’t sure initially what the localfile$1.class was and just presumed it was a temporary file of some sort. It was however a class file corresponding to the anonymous class within the doPrilileged block and needed to be included in the .jar file and properly signed.
So anyway, html file is as before, and final java file is as follows:
localfile.java
I also found that there was no need to have the javascript in the html file create the applet and insert it into the DOM. I think this was mentioned in the link @VGR linked to but it worked for me without it.
Thanks for all the help guys!