org.mozilla.javascript

Class ContextFactory


public class ContextFactory
extends java.lang.Object

Factory class that Rhino runtime use to create new Context instances or to notify about Context execution.

When 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_PROPRTIES:
                 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 scope, Scriptable thisObj, Object[] args)
     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.

Method Summary

void
addListener(ContextFactory.Listener listener)
Object
call(ContextAction action)
Call ContextAction.run(Context cx) using the Context instance associated with the current thread.
protected void
checkNotSealed()
protected GeneratedClassLoader
createClassLoader(ClassLoader parent)
Create class loader for generated classes.
protected Object
doTopCall(Callable callable, Context cx, Scriptable scope, Scriptable thisObj, Object[] args)
Execute top call to script or function.
ClassLoader
getApplicationClassLoader()
Get ClassLoader to use when searching for Java classes.
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(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.

Method Details

addListener

public final void addListener(ContextFactory.Listener listener)

call

public final 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)

checkNotSealed

protected final void checkNotSealed()

createClassLoader

protected GeneratedClassLoader createClassLoader(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.

doTopCall

protected Object doTopCall(Callable callable,
                           Context cx,
                           Scriptable scope,
                           Scriptable thisObj,
                           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.

getApplicationClassLoader

public final ClassLoader getApplicationClassLoader()

getGlobal

public static ContextFactory getGlobal()
Get global 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.

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.

initApplicationClassLoader

public final void initApplicationClassLoader(ClassLoader loader)
Set explicit class loader to use when searching for Java classes.

initGlobal

public static void initGlobal(ContextFactory factory)
Set global ContextFactory. The method can only be called once.

isSealed

public final boolean isSealed()
Checks if this is a sealed ContextFactory.

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.

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)

removeListener

public final void removeListener(ContextFactory.Listener listener)

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.