Thread: JApplet (java runtime permissions)

My jar file will not run citing (Java.lang.RuntimePermissions exit VM.0). My web host (host gator) claims it is because the plan I purchased doesn't support tomcat, but does an applet need tomcat? I just thought I would come to you folks to see if they were jerking me around. I suppose I was wrong if applets require tomcat, because I thought that was for specific server side processing.



**********Solution***************

I had already solved this actually, but thanks to the helpful people here I got a stack trace I used to find the source. Essentially unless you have server side programs set up to send your applet information, you will be unable to access server resources (with my-and similar-hosting plan). So you just wrap your program in a jar file and use the class meta data from Class API to receive your jars information.

getClass().getResourceAsStream("path/to/what/you/need/in/your/jar")

That is good for retrieving information as an inputStream, however you will need an instance of your class to do this.

An applet is embedded within the html of a webpage, and ran on the client (browser). I could be wrong, but that exception suggests you are trying to run the jar file on the server, which your web host does not support. I'd recommend detailing exactly what you are trying to do, and where that Exception is being thrown (server, browser, your jvm?)

Judging from the questions you've asked in your other posts, are you sure you're running an applet?

An applet runs client-side, not on the server. How are you running the applet?

An applet does not need tomcat. Java EE (including JSP) requires Tomcat (or something similar) to run Java on the server. Which one are you trying to do?

HostGator does not support Tomcat, or any other technology that supports running Java on the server. You shouldn't need that for an applet. But you shouldn't be running an applet on your server in the first place.

What **exactly** are you trying to do?

Then that's not running on your server. The problem has nothing to do with HostGator. They were probably confused by your question in the first place, since running the applet has nothing to do with them.

You need to post your code (as an MCVE, not your whole project) as well as the full stack trace, and we'll go from there.

What does a runtime permissions exception suggest? I do not even know what to post for that sort of exception? My jar compiling? I am reading through this, because I have no idea what this exception suggests-hopefully it will give me some insight.

It doesn't really suggest anything. Only a full stack trace and an MCVE will suggest something. What does your Java console say?

Like I said in your previous posts, applets are pretty much dead. Are you signing your jar? Do you have a paid certificate or are you modifying your Java security settings?

Have you tried googling this stuff?

You need to show your Java console, which I mentioned above. Here is the first result for googling "Java console": https://www.java.com/en/download/help/javaconsole.xml

Have you done any of the other stuff I mentioned you need to do?

Originally Posted by KAJLogic

I solved the issue. Now I am just curious about something, and I don't want to create a whole new thread. (solution to my problem is at the top)

While your solution will work and might be the best way to go about it, your diagnosis of the problem seems off. You should be able to read stuff from a URL. You just have to read it correctly.

Originally Posted by KAJLogic

My applet runs in a new window; is there a way to embed it into the browser/web document? I mean so that the window is actually drawn into the browser.

Use a JApplet instead of a JFrame. If you can't get that to work, or if you think you're already using a JApplet, then post the MCVE.

Originally Posted by KevinWorkman

While your solution will work and might be the best way to go about it, your diagnosis of the problem seems off. You should be able to read stuff from a URL. You just have to read it correctly.

I think my host blocks executable programs from accessing my server (due to it being a shared hosting plan). Does this sound right, because this is the conclusion i have come to. They also don't have any support for java server side, so using a program to listen for requests from the client isn't an option..

Use a JApplet instead of a JFrame. If you can't get that to work, or if you think you're already using a JApplet, then post the MCVE.

You're exactly right. Speaking of is the JApplet's paint(Graphics) method any less robust then JFrame's? As in, control over the graphics object etcetera?

Originally Posted by KAJLogic

I think my host blocks executable programs from accessing my server (due to it being a shared hosting plan). Does this sound right, because this is the conclusion i have come to. They also don't have any support for java server side, so using a program to listen for requests from the client isn't an option..

That doesn't make sense. Can you not access the files from the web?

Originally Posted by KAJLogic

You're exactly right. Speaking of is the JApplet's paint(Graphics) method any less robust then JFrame's? As in, control over the graphics object etcetera?

The short answer is no. What have you tried?

The longer answer is that in either case, you shouldn't really need the paint() method of either JApplet or JFrame. Write a class that extends JPanel and overrides paintComponent() and use that instead.

Originally Posted by KAJLogic

I believe that my applet doesn't have the required permission from read from the server.

There seems to be a lot of guesswork with all of this. What specific permissions do you have? What permissions do you think you need to have in order to read from a url on your server?

Originally Posted by KAJLogic

Of course, but can I typecast graphics from paint, can I re assign the graphics object to an extend class I have made (I have a custom graphics object: because I need specific geometric functions graphics/graphics2D doesn't have)

I'm not even sure what that means. You can't cast any instance to another type unless that instance was *already* that type.