/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Rhino code, released
* May 6, 1998.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 1997-2000
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Norris Boyd
*
* Alternatively, the contents of this file may be used under the terms of
* the GNU General Public License Version 2 or later (the "GPL"), in which
* case the provisions of the GPL are applicable instead of those above. If
* you wish to allow use of your version of this file only under the terms of
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* MPL, indicate your decision by deleting the provisions above and replacing
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* not delete the provisions above, a recipient may use your version of this
* file under either the MPL or the GPL.
*
* ***** END LICENSE BLOCK ***** */
import org.mozilla.javascript.*;
/**
* Example of controlling the JavaScript with multiple scopes and threads.
*/
public class DynamicScopes {
static boolean useDynamicScope;
static class MyFactory extends ContextFactory
{
protected boolean hasFeature(Context cx, int featureIndex)
{
if (featureIndex == Context.FEATURE_DYNAMIC_SCOPE) {
return useDynamicScope;
}
return super.hasFeature(cx, featureIndex);
}
}
static {
ContextFactory.initGlobal(new MyFactory());
}
/**
* Main entry point.
*
* Set up the shared scope and then spawn new threads that execute
* relative to that shared scope. Try to run functions with and
* without dynamic scope to see the effect.
*
* The expected output is
* <pre>
* sharedScope
* nested:sharedScope
* sharedScope
* nested:sharedScope
* sharedScope
* nested:sharedScope
* thread0
* nested:thread0
* thread1
* nested:thread1
* thread2
* nested:thread2
* </pre>
* The final three lines may be permuted in any order depending on
* thread scheduling.
*/
public static void main(String[] args)
{
Context cx = Context.enter();
try {
// Precompile source only once
String source = ""
+"var x = 'sharedScope';\n"
+"function f() { return x; }\n"
// Dynamic scope works with nested function too
+"function initClosure(prefix) {\n"
+" return function test() { return prefix+x; }\n"
+"}\n"
+"var closure = initClosure('nested:');\n"
+"";
Script script = cx.compileString(source, "sharedScript", 1, null);
useDynamicScope = false;
runScripts(cx, script);
useDynamicScope = true;
runScripts(cx, script);
} finally {
Context.exit();
}
}
static void runScripts(Context cx, Script script)
{
// Initialize the standard objects (Object, Function, etc.)
// This must be done before scripts can be executed. The call
// returns a new scope that we will share.
ScriptableObject sharedScope = cx.initStandardObjects(null, true);
// Now we can execute the precompiled script against the scope
// to define x variable and f function in the shared scope.
script.exec(cx, sharedScope);
// Now we spawn some threads that execute a script that calls the
// function 'f'. The scope chain looks like this:
// <pre>
// ------------------ ------------------
// | per-thread scope | -prototype-> | shared scope |
// ------------------ ------------------
// ^
// |
// parentScope
// |
// ------------------
// | f's activation |
// ------------------
// </pre>
// Both the shared scope and the per-thread scope have variables 'x'
// defined in them. If 'f' is compiled with dynamic scope enabled,
// the 'x' from the per-thread scope will be used. Otherwise, the 'x'
// from the shared scope will be used. The 'x' defined in 'g' (which
// calls 'f') should not be seen by 'f'.
final int threadCount = 3;
Thread[] t = new Thread[threadCount];
for (int i=0; i < threadCount; i++) {
String source2 = ""
+"function g() { var x = 'local'; return f(); }\n"
+"java.lang.System.out.println(g());\n"
+"function g2() { var x = 'local'; return closure(); }\n"
+"java.lang.System.out.println(g2());\n"
+"";
t[i] = new Thread(new PerThread(sharedScope, source2,
"thread" + i));
}
for (int i=0; i < threadCount; i++)
t[i].start();
// Don't return in this thread until all the spawned threads have
// completed.
for (int i=0; i < threadCount; i++) {
try {
t[i].join();
} catch (InterruptedException e) {
}
}
}
static class PerThread implements Runnable {
PerThread(Scriptable sharedScope, String source, String x) {
this.sharedScope = sharedScope;
this.source = source;
this.x = x;
}
public void run() {
// We need a new Context for this thread.
Context cx = Context.enter();
try {
// We can share the scope.
Scriptable threadScope = cx.newObject(sharedScope);
threadScope.setPrototype(sharedScope);
// We want "threadScope" to be a new top-level
// scope, so set its parent scope to null. This
// means that any variables created by assignments
// will be properties of "threadScope".
threadScope.setParentScope(null);
// Create a JavaScript property of the thread scope named
// 'x' and save a value for it.
threadScope.put("x", threadScope, x);
cx.evaluateString(threadScope, source, "threadScript", 1, null);
} finally {
Context.exit();
}
}
private Scriptable sharedScope;
private String source;
private String x;
}
}
