org.mozilla.javascript.ContextFactory Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of rhino Show documentation
Show all versions of rhino Show documentation
Rhino is an open-source implementation of JavaScript written entirely in Java. It is typically
embedded into Java applications to provide scripting to end users.
/* -*- 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 ContextFactory can also notify listeners
* about context creation and release.
*
* 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)}.
*
* 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)}.
*
* 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.
*
* 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);
* }
*
* }
*
*/
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;
}
public interface GlobalSetter {
public void setContextFactoryGlobal(ContextFactory factory);
public ContextFactory getContextFactoryGlobal();
}
public synchronized static 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. makeContext() 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;
}
// It is a bug to call the method with unknown featureIndex
throw new IllegalArgumentException(String.valueOf(featureIndex));
}
private static 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 Context 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"
);
}
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(final ClassLoader parent)
{
return AccessController.doPrivileged(new PrivilegedAction() {
@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 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.
*
* Calling enterContext() 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
* enterContext() must have a matching call to
* {@link Context#exit()}.
*
* Context cx = contextFactory.enterContext();
* try {
* ...
* cx.evaluateString(...);
* } finally {
* Context.exit();
* }
*
* Instead of using enterContext(), exit() pair consider
* using {@link #call(ContextAction)} which guarantees proper association
* of Context instances with the current thread.
* With this method the above example becomes:
*
* ContextFactory.call(new ContextAction() {
* public Object run(Context cx) {
* ...
* cx.evaluateString(...);
* return null;
* }
* });
*
* @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.
*
* The same as enterContext() except that cx
* is associated with the current thread and returned if the current thread
* has no associated context and cx 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 cx is already associated
* with a different thread
*/
public final Context enterContext(Context cx)
{
return Context.enter(cx, this);
}
}
© 2015 - 2024 Weber Informatics LLC | Privacy Policy