ContextFactory (Rhino)
Keywords: org.mozilla.javascript.ContextFactory class

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## org.mozilla.javascript
Class ContextFactory

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

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.
`java.lang.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(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.

### 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)`

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