Java Doc for ContextFactory.java in  » Scripting » rhino » org » mozilla » javascript » Java Source Code / Java DocumentationJava Source Code and Java Documentation

When the Rhino runtime needs to create new Context instance during execution of Context.enter or Context , it will call ContextFactory.makeContext() of the current global ContextFactory. See ContextFactory.getGlobal() and ContextFactory.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 ContextFactory.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 
ContextFactory.makeContext() protected Context makeContext()
 {
 MyContext cx = new MyContext();
 // Use pure interpreter mode to allow for
 // 
ContextFactory.observeInstructionCount(Context,int)  to work
 cx.setOptimizationLevel(-1);
 // Make Rhino runtime to call observeInstructionCount
 // each 10000 bytecode instructions
 cx.setInstructionObserverThreshold(10000);
 return cx;
 }
 // Override 
ContextFactory.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 
ContextFactory.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 
ContextFactory.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);
 }
 }
 

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();
 }
 

 ContextFactory.call(new ContextAction() {
 public Object run(Context cx) {
 ...
 cx.evaluateString(...);
 return null;
 }
 });
 

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 a Context associated with the current thread
See Also:   ContextFactory.enterContext()
See Also:   ContextFactory.call(ContextAction)
throws:
  IllegalStateException - if cx is already associatedwith a different thread