gnu.app.Zion Maven / Gradle / Ivy
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package gnu.app;
import gnu.util.Misc;
import java.io.BufferedReader;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
/**
* The last mainframe on earth.
*
* Allow execute multiple JVM processors in a single VM, hence acting as
* "the last mainframe" (from the movie Matrix). This can be helpful for
* frequent invocations of Java applications during development, especially
* when (my IBM 1.3) JVM is horribly slow for startup. It also helps if you
* run a destop-full of Java programs, which will otherwise drain all your
* system resources. This program is inspired by the full-blown "free
* multiprocess system in Java", Echidna, by Luke Gorrie.
*
* At the zion> prompt, simply type in the classname
* optionally with its command-line arguments, Zion will run it as a
* sub-thread. Exit Zion with the command "exit". For example,
* to (1) display the help of gnu.x11.test.Hello, (2) run it,
* and (3) run gnu.app.displayhack.Munch all concurrently in the
* same JVM session.
*
*
Because of the way Java loads and caches classes, Zion provides
* another command "reset", such that, for instance, old
* versions of development classes can be discarded and then new versions
* can be executed without exiting and re-entering Zion. A shortcut command
* to reset and execute a class is prepended the command with
* "=". For example, to reset and load
* gnu.x11.test.Hello, do zion>
* =gnu.x11.test.Hello.
*
* @see
* sample output
*
* @see
* help output
*/
public class Zion extends Application {
public Zion (String [] args) {
super (args);
about ("0.1", "the last mainframe on earth",
"Stephen Tse ",
"http://escher.sourceforge.net/",
"\nCommands: "
+ "\n exit: terminate Zion"
+ "\n reset: clear cached classes"
+ "\n CLASSNAME [OPTION]...: execute class with options");
if (help_option) return;
}
public void exec () throws IOException, ClassNotFoundException {
System.setSecurityManager (new SecurityManager ());
BufferedReader br = new BufferedReader (
new java.io.InputStreamReader (System.in));
while (true) {
System.out.print ("zion> ");
String command = br.readLine ();
if (command == null) exit ();
if (Misc.empty (command)) continue;
if (command.equals ("reset"))
gnu.util.ReloadableClassLoader.reset ();
else if (command.equals ("exit")) exit ();
else {
// possbily reset
if (command.charAt (0) == '=') {
gnu.util.ReloadableClassLoader.reset ();
command = command.substring (1, command.length ());
}
// execute subvm
int from = command.indexOf (' ');
if (from == -1)
new SubVM (command, new String [0]);
else {
String args0 = command.substring (from, command.length ());
String [] args1 = Misc.tokenize (args0);
String name = command.substring (0, from);
new SubVM (name, args1);
}
}
}
}
public void exit () {
System.setSecurityManager (null);
System.exit (0);
}
public static void main (String [] args)
throws IOException, ClassNotFoundException {
new Zion (args).exec ();
}
}
class SubVM extends Thread {
public String [] args;
public java.lang.reflect.Method main;
public SubVM (String name, String [] args) {
this.args = args;
try {
// Class.forName() uses loaded class instead of asking class loader
Class klass = gnu.util.ReloadableClassLoader
.instance.loadClass (name);
Class [] para_types = new Class [] {String [].class};
main = klass.getDeclaredMethod ("main", para_types);
start ();
} catch (Exception e) {
e.printStackTrace ();
}
}
public void run () {
if (main == null) return;
try {
main.invoke (null, new Object [] {args});
} catch (Exception e) {
// safely ignored sub vm exit
// FIXME: it can't catch exceptions thrown in other threads
if (e instanceof InvocationTargetException) {
InvocationTargetException e0 = (InvocationTargetException) e;
Throwable e1 = e0.getTargetException ();
if (e1 instanceof SecurityManager.SubVMExitException) return;
}
e.printStackTrace ();
}
}
}
/** A dummy security manager for Zion. */
class SecurityManager extends java.lang.SecurityManager {
/** Thrown when a sub VM calls {@link java.lang.System#exit(int)}. */
public class SubVMExitException extends SecurityException {}
public void checkExit (int status) {
// throw an exception such that `System.exit()' fails
throw new SubVMExitException ();
}
/** Override to disable all permission checkings for Zion. */
public void checkPermission (java.security.Permission perm) {}
}