Javaspaces Applet Help
From: Joe (zief_at_yahoo.com)
Date: 04/12/04
- Next message: B Young: "Ghost image drawing- how to optimize?"
- Previous message: Bill Scott: "Re: java.NIO + select + Network Interface Down = 100% CPU Usage"
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
Date: 12 Apr 2004 11:26:34 -0700
Hi,
I don't know if there are any JavaSpaces experts on this group, but if
there are I'd be gratefully for any help on the following problem:
I am trying to get applets working in web browsers, at least IE if
possible, which can then access JavaSpaces on the server, download an
object, compute the result, then post it back.
However, I am having a bit of a nightmare with all this. I have
searched these postings, and on Google/Groups and can't find a simple
guide to achieving it.
I have started as simple as possible, with the HelloWorldTwo example
from the JavaSpaces Principles, Patterns and Practice book. I can get
this working perfectly fine on my computer and over my local network
at the command line. So I then converted the client into a very simple
applet.
This can also be run on any machine on the LAN through appletviewer
with the following command:
java -Djava.security.policy=applet\policy\policy.all
-Doutrigger.spacename=JavaSpaces -Dcom.sun.jini.lookup.groups=public
-Djava.rmi.server.codebase=http://192.168.0.1:8081/space-examples-dl.jar
sun.applet.AppletViewer runjs.jsp
Where runjs.jsp simply contains the appropriate applet tag and the
class to load.
However, when I came to try and get this working through a browser
(which is essential to get working for my dissertation university
project), I am having a lot of problems.
I am using Tomcat webserver for my Jsp pages, but I have decided to
still use the server program in tools.jar (In the running
Javaspaces1_2_1 example), I don't know if this will effect things, it
is on port 8081 while tomcat is on 8080?
Reluctantly (I'd rather not change default permissions for Java
runtime, so it will work on any computer automatically), I added some
permissions to the java.policy file in the J2RE folder. These
permissions were:
permission java.util.PropertyPermission "com.sun.jini.lookup.locator",
"read";
permission java.util.PropertyPermission "com.sun.jini.lookup.groups",
"read";
permission java.net.NetPermission
"net.jini.discovery.DiscoveryPermission";
permission java.util.PropertyPermission
"net.jini.discovery.DiscoveryPermission", "read, write";
This has got rid of several of the errors, but I am now getting a
LookupLocator: find: access denied
(net.jini.discovery.DiscoveryPermission )
java.security.AccessControlException: access denied
(net.jini.discovery.DiscoveryPermission ) at
java.security.AccessControlContext.checkPermission(Unknown
Source)......
which I can't seem to sort out by adding permissions to the policy
file.
As I say, I'd rather not change these permissions, so if anyone can
tell me if there is an easier way I'd be extremely grateful, if not,
any help with this error will also be great.
Also if I can get this eventually working, I am hoping to include all
files required, both my project and the needed jini files, in one JAR
file, so anyone running the applet need not install jini and
classpaths. I think I have identified most of the files I need, but
any further information on this will be excellent.
Thankyou very much for your time in advance,
Joe
ps.. files which I am using to try and get this working are below:
The server in effect, HelloWorld.java
import net.jini.core.lease.Lease;
import net.jini.space.JavaSpace;
public class HelloWorld {
public static void main(String[] args) {
try {
Message msg = new Message("Hello World", 0);
JavaSpace space = SpaceAccessor.getSpace();
space.write(msg, null, Lease.FOREVER);
Message template = new Message();
for (;;) {
Message result = (Message)
space.read(template, null, Long.MAX_VALUE);
System.out.println(result);
Thread.sleep(1000);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
The client applet HelloWorldClient.java
import net.jini.core.lease.Lease;
import net.jini.space.JavaSpace;
import java.applet.Applet;
import java.io.IOException;
import java.net.InetAddress;
public class HelloWorldClient extends Applet
{
public void init()
{
super.init();
// find out who I am
InetAddress myAddr = null;
String myHost;
try
{
myAddr = InetAddress.getLocalHost();
myHost = myAddr.getHostName();
}
catch (java.net.UnknownHostException e)
{
if (myAddr != null)
myHost = myAddr.toString();
else
myHost = "localhost";
}
System.out.println("I am running on " + myHost);
try
{
JavaSpace space = SpaceAccessor.getSpace("JavaSpaces");
Message template = new Message();
for (;;)
{
System.out.println("Getting object");
Message result = (Message)space.take(template, null,
Long.MAX_VALUE);
System.out.println("Got object");
result.increment();
space.write(result, null, Lease.FOREVER);
System.out.println("Wrote object back");
Thread.sleep(1000);
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
Message.java
import net.jini.core.entry.Entry;
public class Message implements Entry {
public String content;
public Integer counter;
public Message() {
}
public Message(String content, int initVal) {
this.content = content;
counter = new Integer(initVal);
}
public String toString() {
return content + " read " + counter + " times.";
}
public void increment() {
counter = new Integer(counter.intValue() + 1);
}
}
SpaceAccessor.java
import java.rmi.*;
import net.jini.space.JavaSpace;
import com.sun.jini.mahout.Locator;
import com.sun.jini.outrigger.Finder;
public class SpaceAccessor
{
public static JavaSpace getSpace(String name)
{
try
{
if (System.getSecurityManager() == null)
{
System.out.println("Getting security manager");
System.setSecurityManager(new RMISecurityManager());
}
Locator locator = new com.sun.jini.outrigger.DiscoveryLocator();
Finder finder = new com.sun.jini.outrigger.LookupFinder();
return (JavaSpace)finder.find(locator, name);
}
catch (Exception e)
{
System.err.println(e.getMessage());
}
return null;
}
public static JavaSpace getSpace()
{
return getSpace("JavaSpaces");
}
}
- Next message: B Young: "Ghost image drawing- how to optimize?"
- Previous message: Bill Scott: "Re: java.NIO + select + Network Interface Down = 100% CPU Usage"
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
Relevant Pages
|
