ContextFactory.java
/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
// API class
package org.mozilla.javascript;
import java.security.AccessController;
import java.security.PrivilegedAction;
/**
* 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 static synchronized void initGlobal(ContextFactory factory) {
if (factory == null) {
throw new IllegalArgumentException();
}
if (hasCustomGlobal) {
throw new IllegalStateException();
}
hasCustomGlobal = true;
global = factory;
}
public interface GlobalSetter {
public void setContextFactoryGlobal(ContextFactory factory);
public ContextFactory getContextFactoryGlobal();
}
public static synchronized GlobalSetter getGlobalSetter() {
if (hasCustomGlobal) {
throw new IllegalStateException();
}
hasCustomGlobal = true;
class GlobalSetterImpl implements GlobalSetter {
@Override
public void setContextFactoryGlobal(ContextFactory factory) {
global = factory == null ? new ContextFactory() : factory;
}
@Override
public ContextFactory getContextFactoryGlobal() {
return global;
}
}
return new GlobalSetterImpl();
}
/**
* 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. <code>makeContext()</code> 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 true;
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;
case Context.FEATURE_V8_EXTENSIONS:
return true;
case Context.FEATURE_OLD_UNDEF_NULL_THIS:
return cx.getLanguageVersion() <= Context.VERSION_1_7;
case Context.FEATURE_ENUMERATE_IDS_FIRST:
return cx.getLanguageVersion() >= Context.VERSION_ES6;
case Context.FEATURE_THREAD_SAFE_OBJECTS:
return false;
case Context.FEATURE_INTEGER_WITHOUT_DECIMAL_PLACE:
return false;
case Context.FEATURE_LITTLE_ENDIAN:
return false;
case Context.FEATURE_ENABLE_XML_SECURE_PARSING:
return true;
case Context.FEATURE_ENABLE_JAVA_MAP_ACCESS:
return false;
case Context.FEATURE_INTL_402:
return false;
}
// It is a bug to call the method with unknown featureIndex
throw new IllegalArgumentException(String.valueOf(featureIndex));
}
/**
* 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(final ClassLoader parent) {
return AccessController.doPrivileged(
new PrivilegedAction<DefiningClassLoader>() {
@Override
public DefiningClassLoader run() {
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) {
Object result = callable.call(cx, scope, thisObj, args);
return result instanceof ConsString ? result.toString() : result;
}
/**
* 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 <T> T call(ContextAction<T> 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 <code>enterContext()</code>, <code>exit()</code> 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
*/
@Deprecated
public final Context enter() {
return enterContext(null);
}
/**
* @deprecated Use {@link Context#exit()} instead.
*/
@Deprecated
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);
}
}