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CaRMtl/org/mozilla/javascript/ContextFactory.java

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/* -*- 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, 1999.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 1997-1999
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Igor Bukanov, igor@fastmail.fm
*
* 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
* the GPL and not to allow others to use your version of this file under the
* MPL, indicate your decision by deleting the provisions above and replacing
* them with the notice and other provisions required by the GPL. If you do
* not delete the provisions above, a recipient may use your version of this
* file under either the MPL or the GPL.
*
* ***** END LICENSE BLOCK ***** */
// API class
package org.mozilla.javascript;
/**
* Factory class that Rhino runtime uses to create new {@link Context}
* instances. A <code>ContextFactory</code> can also notify listeners
* about context creation and release.
* <p>
* When the Rhino runtime needs to create new {@link Context} instance during
* execution of {@link Context#enter()} or {@link Context}, it will call
* {@link #makeContext()} of the current global ContextFactory.
* See {@link #getGlobal()} and {@link #initGlobal(ContextFactory)}.
* <p>
* It is also possible to use explicit ContextFactory instances for Context
* creation. This is useful to have a set of independent Rhino runtime
* instances under single JVM. See {@link #call(ContextAction)}.
* <p>
* The following example demonstrates Context customization to terminate
* scripts running more then 10 seconds and to provide better compatibility
* with JavaScript code using MSIE-specific features.
* <pre>
* import org.mozilla.javascript.*;
*
* class MyFactory extends ContextFactory
* {
*
* // Custom {@link Context} to store execution time.
* private static class MyContext extends Context
* {
* long startTime;
* }
*
* static {
* // Initialize GlobalFactory with custom factory
* ContextFactory.initGlobal(new MyFactory());
* }
*
* // Override {@link #makeContext()}
* protected Context makeContext()
* {
* MyContext cx = new MyContext();
* // Make Rhino runtime to call observeInstructionCount
* // each 10000 bytecode instructions
* cx.setInstructionObserverThreshold(10000);
* return cx;
* }
*
* // Override {@link #hasFeature(Context, int)}
* public boolean hasFeature(Context cx, int featureIndex)
* {
* // Turn on maximum compatibility with MSIE scripts
* switch (featureIndex) {
* case {@link Context#FEATURE_NON_ECMA_GET_YEAR}:
* return true;
*
* case {@link Context#FEATURE_MEMBER_EXPR_AS_FUNCTION_NAME}:
* return true;
*
* case {@link Context#FEATURE_RESERVED_KEYWORD_AS_IDENTIFIER}:
* return true;
*
* case {@link Context#FEATURE_PARENT_PROTO_PROPERTIES}:
* return false;
* }
* return super.hasFeature(cx, featureIndex);
* }
*
* // Override {@link #observeInstructionCount(Context, int)}
* protected void observeInstructionCount(Context cx, int instructionCount)
* {
* MyContext mcx = (MyContext)cx;
* long currentTime = System.currentTimeMillis();
* if (currentTime - mcx.startTime > 10*1000) {
* // More then 10 seconds from Context creation time:
* // it is time to stop the script.
* // Throw Error instance to ensure that script will never
* // get control back through catch or finally.
* throw new Error();
* }
* }
*
* // Override {@link #doTopCall(Callable,
Context, Scriptable,
Scriptable, Object[])}
* protected Object doTopCall(Callable callable,
* Context cx, Scriptable scope,
* Scriptable thisObj, Object[] args)
* {
* MyContext mcx = (MyContext)cx;
* mcx.startTime = System.currentTimeMillis();
*
* return super.doTopCall(callable, cx, scope, thisObj, args);
* }
*
* }
*
* </pre>
*/
public class ContextFactory
{
private static volatile boolean hasCustomGlobal;
private static ContextFactory global = new ContextFactory();
private volatile boolean sealed;
private final Object listenersLock = new Object();
private volatile Object listeners;
private boolean disabledListening;
private ClassLoader applicationClassLoader;
/**
* Listener of {@link Context} creation and release events.
*/
public interface Listener
{
/**
* Notify about newly created {@link Context} object.
*/
public void contextCreated(Context cx);
/**
* Notify that the specified {@link Context} instance is no longer
* associated with the current thread.
*/
public void contextReleased(Context cx);
}
/**
* Get global ContextFactory.
*
* @see #hasExplicitGlobal()
* @see #initGlobal(ContextFactory)
*/
public static ContextFactory getGlobal()
{
return global;
}
/**
* Check if global factory was set.
* Return true to indicate that {@link #initGlobal(ContextFactory)} was
* already called and false to indicate that the global factory was not
* explicitly set.
*
* @see #getGlobal()
* @see #initGlobal(ContextFactory)
*/
public static boolean hasExplicitGlobal()
{
return hasCustomGlobal;
}
/**
* Set global ContextFactory.
* The method can only be called once.
*
* @see #getGlobal()
* @see #hasExplicitGlobal()
*/
public synchronized static void initGlobal(ContextFactory factory)
{
if (factory == null) {
throw new IllegalArgumentException();
}
if (hasCustomGlobal) {
throw new IllegalStateException();
}
hasCustomGlobal = true;
global = factory;
}
/**
* Create new {@link Context} instance to be associated with the current
* thread.
* This is a callback method used by Rhino to create {@link Context}
* instance when it is necessary to associate one with the current
* execution thread. <tt>makeContext()</tt> is allowed to call
* {@link Context#seal(Object)} on the result to prevent
* {@link Context} changes by hostile scripts or applets.
*/
protected Context makeContext()
{
return new Context(this);
}
/**
* Implementation of {@link Context#hasFeature(int featureIndex)}.
* This can be used to customize {@link Context} without introducing
* additional subclasses.
*/
protected boolean hasFeature(Context cx, int featureIndex)
{
int version;
switch (featureIndex) {
case Context.FEATURE_NON_ECMA_GET_YEAR:
/*
* During the great date rewrite of 1.3, we tried to track the
* evolving ECMA standard, which then had a definition of
* getYear which always subtracted 1900. Which we
* implemented, not realizing that it was incompatible with
* the old behavior... now, rather than thrash the behavior
* yet again, we've decided to leave it with the - 1900
* behavior and point people to the getFullYear method. But
* we try to protect existing scripts that have specified a
* version...
*/
version = cx.getLanguageVersion();
return (version == Context.VERSION_1_0
|| version == Context.VERSION_1_1
|| version == Context.VERSION_1_2);
case Context.FEATURE_MEMBER_EXPR_AS_FUNCTION_NAME:
return false;
case Context.FEATURE_RESERVED_KEYWORD_AS_IDENTIFIER:
return false;
case Context.FEATURE_TO_STRING_AS_SOURCE:
version = cx.getLanguageVersion();
return version == Context.VERSION_1_2;
case Context.FEATURE_PARENT_PROTO_PROPERTIES:
return true;
case Context.FEATURE_E4X:
version = cx.getLanguageVersion();
return (version == Context.VERSION_DEFAULT
|| version >= Context.VERSION_1_6);
case Context.FEATURE_DYNAMIC_SCOPE:
return false;
case Context.FEATURE_STRICT_VARS:
return false;
case Context.FEATURE_STRICT_EVAL:
return false;
case Context.FEATURE_LOCATION_INFORMATION_IN_ERROR:
return false;
case Context.FEATURE_STRICT_MODE:
return false;
case Context.FEATURE_WARNING_AS_ERROR:
return false;
case Context.FEATURE_ENHANCED_JAVA_ACCESS:
return false;
}
// It is a bug to call the method with unknown featureIndex
throw new IllegalArgumentException(String.valueOf(featureIndex));
}
private boolean isDom3Present() {
Class<?> nodeClass = Kit.classOrNull("org.w3c.dom.Node");
if (nodeClass == null) return false;
// Check to see whether DOM3 is present; use a new method defined in
// DOM3 that is vital to our implementation
try {
nodeClass.getMethod("getUserData", new Class<?>[] { String.class });
return true;
} catch (NoSuchMethodException e) {
return false;
}
}
/**
* Provides a default
* {@link org.mozilla.javascript.xml.XMLLib.Factory XMLLib.Factory}
* to be used by the <code>Context</code> instances produced by this
* factory. See {@link Context#getE4xImplementationFactory} for details.
*
* May return null, in which case E4X functionality is not supported in
* Rhino.
*
* The default implementation now prefers the DOM3 E4X implementation.
*/
protected org.mozilla.javascript.xml.XMLLib.Factory
getE4xImplementationFactory()
{
// Must provide default implementation, rather than abstract method,
// so that past implementors of ContextFactory do not fail at runtime
// upon invocation of this method.
// Note that the default implementation returns null if we
// neither have XMLBeans nor a DOM3 implementation present.
if (isDom3Present()) {
return org.mozilla.javascript.xml.XMLLib.Factory.create(
"org.mozilla.javascript.xmlimpl.XMLLibImpl"
);
} else if (Kit.classOrNull("org.apache.xmlbeans.XmlCursor") != null) {
return org.mozilla.javascript.xml.XMLLib.Factory.create(
"org.mozilla.javascript.xml.impl.xmlbeans.XMLLibImpl"
);
} else {
return null;
}
}
/**
* Create class loader for generated classes.
* This method creates an instance of the default implementation
* of {@link GeneratedClassLoader}. Rhino uses this interface to load
* generated JVM classes when no {@link SecurityController}
* is installed.
* Application can override the method to provide custom class loading.
*/
protected GeneratedClassLoader createClassLoader(ClassLoader parent)
{
return new DefiningClassLoader(parent);
}
/**
* Get ClassLoader to use when searching for Java classes.
* Unless it was explicitly initialized with
* {@link #initApplicationClassLoader(ClassLoader)} the method returns
* null to indicate that Thread.getContextClassLoader() should be used.
*/
public final ClassLoader getApplicationClassLoader()
{
return applicationClassLoader;
}
/**
* Set explicit class loader to use when searching for Java classes.
*
* @see #getApplicationClassLoader()
*/
public final void initApplicationClassLoader(ClassLoader loader)
{
if (loader == null)
throw new IllegalArgumentException("loader is null");
if (!Kit.testIfCanLoadRhinoClasses(loader))
throw new IllegalArgumentException(
"Loader can not resolve Rhino classes");
if (this.applicationClassLoader != null)
throw new IllegalStateException(
"applicationClassLoader can only be set once");
checkNotSealed();
this.applicationClassLoader = loader;
}
/**
* Execute top call to script or function.
* When the runtime is about to execute a script or function that will
* create the first stack frame with scriptable code, it calls this method
* to perform the real call. In this way execution of any script
* happens inside this function.
*/
protected Object doTopCall(Callable callable,
Context cx, Scriptable scope,
Scriptable thisObj, Object[] args)
{
return callable.call(cx, scope, thisObj, args);
}
/**
* Implementation of
* {@link Context#observeInstructionCount(int instructionCount)}.
* This can be used to customize {@link Context} without introducing
* additional subclasses.
*/
protected void observeInstructionCount(Context cx, int instructionCount) {
}
protected void onContextCreated(Context cx)
{
Object listeners = this.listeners;
for (int i = 0; ; ++i) {
Listener l = (Listener)Kit.getListener(listeners, i);
if (l == null)
break;
l.contextCreated(cx);
}
}
protected void onContextReleased(Context cx)
{
Object listeners = this.listeners;
for (int i = 0; ; ++i) {
Listener l = (Listener)Kit.getListener(listeners, i);
if (l == null)
break;
l.contextReleased(cx);
}
}
public final void addListener(Listener listener)
{
checkNotSealed();
synchronized (listenersLock) {
if (disabledListening) {
throw new IllegalStateException();
}
listeners = Kit.addListener(listeners, listener);
}
}
public final void removeListener(Listener listener)
{
checkNotSealed();
synchronized (listenersLock) {
if (disabledListening) {
throw new IllegalStateException();
}
listeners = Kit.removeListener(listeners, listener);
}
}
/**
* The method is used only to implement
* Context.disableStaticContextListening()
*/
final void disableContextListening()
{
checkNotSealed();
synchronized (listenersLock) {
disabledListening = true;
listeners = null;
}
}
/**
* Checks if this is a sealed ContextFactory.
* @see #seal()
*/
public final boolean isSealed()
{
return sealed;
}
/**
* Seal this ContextFactory so any attempt to modify it like to add or
* remove its listeners will throw an exception.
* @see #isSealed()
*/
public final void seal()
{
checkNotSealed();
sealed = true;
}
protected final void checkNotSealed()
{
if (sealed) throw new IllegalStateException();
}
/**
* Call {@link ContextAction#run(Context cx)}
* using the {@link Context} instance associated with the current thread.
* If no Context is associated with the thread, then
* {@link #makeContext()} will be called to construct
* new Context instance. The instance will be temporary associated
* with the thread during call to {@link ContextAction#run(Context)}.
*
* @see ContextFactory#call(ContextAction)
* @see Context#call(ContextFactory factory, Callable callable,
* Scriptable scope, Scriptable thisObj,
* Object[] args)
*/
public final Object call(ContextAction action)
{
return Context.call(this, action);
}
/**
* Get a context associated with the current thread, creating one if need
* be. The Context stores the execution state of the JavaScript engine, so
* it is required that the context be entered before execution may begin.
* Once a thread has entered a Context, then getCurrentContext() may be
* called to find the context that is associated with the current thread.
* <p>
* Calling <code>enterContext()</code> will return either the Context
* currently associated with the thread, or will create a new context and
* associate it with the current thread. Each call to
* <code>enterContext()</code> must have a matching call to
* {@link Context#exit()}.
* <pre>
* Context cx = contextFactory.enterContext();
* try {
* ...
* cx.evaluateString(...);
* } finally {
* Context.exit();
* }
* </pre>
* Instead of using <tt>enterContext()</tt>, <tt>exit()</tt> pair consider
* using {@link #call(ContextAction)} which guarantees proper association
* of Context instances with the current thread.
* With this method the above example becomes:
* <pre>
* ContextFactory.call(new ContextAction() {
* public Object run(Context cx) {
* ...
* cx.evaluateString(...);
* return null;
* }
* });
* </pre>
* @return a Context associated with the current thread
* @see Context#getCurrentContext()
* @see Context#exit()
* @see #call(ContextAction)
*/
public Context enterContext()
{
return enterContext(null);
}
/**
* @deprecated use {@link #enterContext()} instead
* @return a Context associated with the current thread
*/
public final Context enter()
{
return enterContext(null);
}
/**
* @deprecated Use {@link Context#exit()} instead.
*/
public final void exit()
{
Context.exit();
}
/**
* Get a Context associated with the current thread, using the given
* Context if need be.
* <p>
* The same as <code>enterContext()</code> except that <code>cx</code>
* is associated with the current thread and returned if the current thread
* has no associated context and <code>cx</code> is not associated with any
* other thread.
* @param cx a Context to associate with the thread if possible
* @return a Context associated with the current thread
* @see #enterContext()
* @see #call(ContextAction)
* @throws IllegalStateException if <code>cx</code> is already associated
* with a different thread
*/
public final Context enterContext(Context cx)
{
return Context.enter(cx, this);
}
}
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