org.mozilla.javascript
Class ContextFactory

java.lang.Object
  org.mozilla.javascript.ContextFactory

public class ContextFactory
extends java.lang.Object

Factory class that Rhino runtime uses to create new Context instances. A ContextFactory can also notify listeners about context creation and release.

When the Rhino runtime needs to create new Context instance during execution of Context.enter() or Context, it will call makeContext() of the current global ContextFactory. See getGlobal() and 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 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 Context to store execution time.
     private static class MyContext extends Context
     {
         long startTime;
     }

     static {
         // Initialize GlobalFactory with custom factory
         ContextFactory.initGlobal(new MyFactory());
     }

     // Override makeContext()
     protected Context makeContext()
     {
         MyContext cx = new MyContext();
         // Use pure interpreter mode to allow for
         // observeInstructionCount(Context, int) to work
         cx.setOptimizationLevel(-1);
         // Make Rhino runtime to call observeInstructionCount
         // each 10000 bytecode instructions
         cx.setInstructionObserverThreshold(10000);
         return cx;
     }

     // Override hasFeature(Context, int)
     public boolean hasFeature(Context cx, int featureIndex)
     {
         // Turn on maximum compatibility with MSIE scripts
         switch (featureIndex) {
             case Context.FEATURE_NON_ECMA_GET_YEAR:
                 return true;

             case Context.FEATURE_MEMBER_EXPR_AS_FUNCTION_NAME:
                 return true;

             case Context.FEATURE_RESERVED_KEYWORD_AS_IDENTIFIER:
                 return true;

             case Context.FEATURE_PARENT_PROTO_PROPERTIES:
                 return false;
         }
         return super.hasFeature(cx, featureIndex);
     }

     // Override 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 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);
     }

 }

 

Nested Class Summary

static interface

ContextFactory.Listener Listener of Context creation and release events.

Constructor Summary

ContextFactory()

Method Summary

void	addListener(ContextFactory.Listener listener)
java.lang.Object	call(ContextAction action) Call ContextAction.run(Context cx) using the Context instance associated with the current thread.
protected void	checkNotSealed()
protected GeneratedClassLoader	createClassLoader(java.lang.ClassLoader parent) Create class loader for generated classes.
protected java.lang.Object	doTopCall(Callable callable, Context cx, Scriptable scope, Scriptable thisObj, java.lang.Object[] args) Execute top call to script or function.
Context	enter() Deprecated. use enterContext() instead
Context	enterContext() Get a context associated with the current thread, creating one if need be.
Context	enterContext(Context cx) Get a Context associated with the current thread, using the given Context if need be.
void	exit() Deprecated. Use Context.exit() instead.
java.lang.ClassLoader	getApplicationClassLoader() Get ClassLoader to use when searching for Java classes.
protected org.mozilla.javascript.xml.XMLLib.Factory	getE4xImplementationFactory() Provides a default XMLLib.Factory to be used by the Context instances produced by this factory.
static ContextFactory	getGlobal() Get global ContextFactory.
static boolean	hasExplicitGlobal() Check if global factory was set.
protected boolean	hasFeature(Context cx, int featureIndex) Implementation of Context.hasFeature(int featureIndex).
void	initApplicationClassLoader(java.lang.ClassLoader loader) Set explicit class loader to use when searching for Java classes.
static void	initGlobal(ContextFactory factory) Set global ContextFactory.
boolean	isSealed() Checks if this is a sealed ContextFactory.
protected Context	makeContext() Create new Context instance to be associated with the current thread.
protected void	observeInstructionCount(Context cx, int instructionCount) Implementation of Context.observeInstructionCount(int instructionCount).
protected void	onContextCreated(Context cx)
protected void	onContextReleased(Context cx)
void	removeListener(ContextFactory.Listener listener)
void	seal() Seal this ContextFactory so any attempt to modify it like to add or remove its listeners will throw an exception.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ContextFactory

public ContextFactory()

Method Detail

getGlobal

public static ContextFactory getGlobal()

Get global ContextFactory.

See Also:

hasExplicitGlobal(), initGlobal(ContextFactory)

hasExplicitGlobal

public static boolean hasExplicitGlobal()

Check if global factory was set. Return true to indicate that initGlobal(ContextFactory) was already called and false to indicate that the global factory was not explicitly set.

See Also:

getGlobal(), initGlobal(ContextFactory)

initGlobal

public static void initGlobal(ContextFactory factory)

Set global ContextFactory. The method can only be called once.

See Also:

getGlobal(), hasExplicitGlobal()

makeContext

protected Context makeContext()

Create new Context instance to be associated with the current thread. This is a callback method used by Rhino to create Context instance when it is necessary to associate one with the current execution thread. makeContext() is allowed to call Context.seal(Object) on the result to prevent Context changes by hostile scripts or applets.

hasFeature

protected boolean hasFeature(Context cx,
                             int featureIndex)

Implementation of Context.hasFeature(int featureIndex). This can be used to customize Context without introducing additional subclasses.

getE4xImplementationFactory

protected org.mozilla.javascript.xml.XMLLib.Factory getE4xImplementationFactory()

Provides a default XMLLib.Factory to be used by the Context instances produced by this factory. See 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.

createClassLoader

protected GeneratedClassLoader createClassLoader(java.lang.ClassLoader parent)

Create class loader for generated classes. This method creates an instance of the default implementation of GeneratedClassLoader. Rhino uses this interface to load generated JVM classes when no SecurityController is installed. Application can override the method to provide custom class loading.

getApplicationClassLoader

public final java.lang.ClassLoader getApplicationClassLoader()

Get ClassLoader to use when searching for Java classes. Unless it was explicitly initialized with initApplicationClassLoader(ClassLoader) the method returns null to indicate that Thread.getContextClassLoader() should be used.

initApplicationClassLoader

public final void initApplicationClassLoader(java.lang.ClassLoader loader)

Set explicit class loader to use when searching for Java classes.

See Also:

getApplicationClassLoader()

doTopCall

protected java.lang.Object doTopCall(Callable callable,
                                     Context cx,
                                     Scriptable scope,
                                     Scriptable thisObj,
                                     java.lang.Object[] args)

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.

observeInstructionCount

protected void observeInstructionCount(Context cx,
                                       int instructionCount)

Implementation of Context.observeInstructionCount(int instructionCount). This can be used to customize Context without introducing additional subclasses.

onContextCreated

protected void onContextCreated(Context cx)

onContextReleased

protected void onContextReleased(Context cx)

addListener

public final void addListener(ContextFactory.Listener listener)

removeListener

public final void removeListener(ContextFactory.Listener listener)

isSealed

public final boolean isSealed()

Checks if this is a sealed ContextFactory.

See Also:

seal()

seal

public final void seal()

Seal this ContextFactory so any attempt to modify it like to add or remove its listeners will throw an exception.

See Also:

isSealed()

checkNotSealed

protected final void checkNotSealed()

call

public final java.lang.Object call(ContextAction action)

Call ContextAction.run(Context cx) using the Context instance associated with the current thread. If no Context is associated with the thread, then makeContext() will be called to construct new Context instance. The instance will be temporary associated with the thread during call to ContextAction.run(Context).

See Also:

call(ContextAction), Context.call(ContextFactory factory, Callable callable, Scriptable scope, Scriptable thisObj, Object[] args)

enterContext

public Context enterContext()

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 Context.exit().

      Context cx = contextFactory.enterContext();
      try {
          ...
          cx.evaluateString(...);
      } finally {
          Context.exit();
      }
 

Instead of using enterContext(), exit() pair consider using 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;
          }
      });
 

Returns:

a Context associated with the current thread

See Also:

Context.getCurrentContext(), Context.exit(), call(ContextAction)

enter

public final Context enter()

Deprecated. use enterContext() instead

Returns:

a Context associated with the current thread

exit

public final void exit()

Deprecated. Use Context.exit() instead.

enterContext

public final Context enterContext(Context cx)

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.

Parameters:

cx - a Context to associate with the thread if possible

Returns:

a Context associated with the current thread

Throws:

java.lang.IllegalStateException - if cx is already associated with a different thread

See Also:

enterContext(), call(ContextAction)