Protecting object identity in a language with built-in synchronization objects

• US 7,458,061 B2
• Filed: 06/12/2003
• Issued: 11/25/2008
• Est. Priority Date: 06/14/2002
• Status: Active Grant

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Bracha, Gilad
• Primary Examiner(s): INGBERG, TODD D
• Application Number:
  US10/459,363
• Publication Number:
  US 20040039746A1
• Time in Patent Office: 1,993 Days
• Field of Search: 717/108, 717/116, 719/312, 719/316, 719/328, 719/315
• US Class Current: 717/116
• CPC Class Codes: G06F 16/289 Object oriented databases
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

Methods and systems for protecting object identity in an object-oriented programming language. An object from a class for protecting object identity is instantiated in memory. The object includes a first method that determines whether two object values are equal, and a second method that overrides an identity method associated with a superclass of the object by invoking the first method, the identity method for determining the identity of two objects. The object is immediately locked in response to the instantiating, so that the identity of the locked object is protected from threads that attempt to synchronize on the locked object.

Claims

1. A process for protecting object identity in an object-oriented programming language, comprising:

instantiating an object from a first class in memory; and

locking the object in response to the instantiating, wherein the identity of the locked object is protected from threads that attempt to synchronize on the locked object, and wherein each object from the first class is automatically locked when that object is instantiated.

2. The process of claim 1, wherein the object includes a first method that determines whether two object values are equal, and a second method that overrides an identity method associated with a superclass of the object by invoking the first method, the identity method for determining the identity of two objects.

3. The process of claim 2, wherein the second method is a final method.

4. The process of claim 1, the locking comprising:

setting a bit in a header of the object using a thread.

5. The process of claim 4, wherein the thread that changes the bit is a system thread that does not run user code.

6. A process for protecting object identity in an object-oriented programming language, comprising:

instantiating an object from a first class in memory, the object including a first method that determines whether two object values are equal, and a second method that overrides an identity method associated with a superclass of the object by invoking the first method, the identity method for determining the identity of two objects; and

locking the object in response to the instantiating, wherein the identity of the locked object is protected from threads that attempt to synchronize on the locked object, and wherein each object from the first class is automatically locked when that object is instantiated.

7. The process of claim 6, wherein the second method is a final method.

8. The process of claim 6, wherein the object includes a third method that returns a hash code for a given object.

9. The process of claim 6, the locking comprising:

changing a bit in a header of the object using a thread.

10. The process of claim 9, wherein the thread that changes the bit is a system thread that does not run user code.

11. A process for protecting object identity in an object-oriented programming language, comprising:

receiving code including an identity operator;

invoking an identity method associated with the identity operator;

performing a first method, instead of the identity method, based on a determination that the identity method is associated with an object from a first class, the first method for determining whether two object values are equal; and

performing an identity function based on a determination that the identity method is not associated with an object from the first class, the identity function for determining whether two object references refer to the same object.

12. The process of claim 11, wherein the identity method associated with the object from the first class is a final method that invokes the first method.

13. The process of claim 11, wherein the object from the first class is locked upon instantiation so that the identity of the locked object is protected from threads that attempt to synchronize on the locked object.

14. An object from a class for protecting object identity in an object-oriented programming language, comprising:

a first method that determines whether two object values are equal; and

a second method that overrides an identity method associated with a superclass of the object by invoking the first method, the identity method for determining the identity of two objects.

15. The object of claim 14, wherein the second method is a final method.

16. The object of claim 14, further comprising:

a third method that returns a hash code for a given object.

17. The object of claim 14, wherein all fields of the object are final.

18. The object of claim 14, wherein the object is locked by a thread upon instantiation, so that the identity of the object is indeterminable.

19. A class hierarchy for protecting object identity in an object-oriented programming language, comprising:

a first class including a first identity method configured to determine identity of two objects;

a second class including a second identity method and an equals method for determining whether two object values are equal, the second identity method overriding the first identity method by invoking the equals method, wherein the second class is a direct abstract subclass of the first class; and

a third class that inherits the second identity method from the second class, wherein the third class is a subclass of the second class and an object from the third class is locked upon instantiation in memory so that the identity of the locked object is protected from threads that attempt to synchronize on the locked object, and wherein each object from the third class is automatically locked when that object is instantiated.

20. The class hierarchy of claim 19, wherein the second identity method is a final method.

21. The class hierarchy of claim 19, wherein the locking thread is a system thread that does not run user code.

22. An object from a class for protecting object identity in an object-oriented programming language, comprising:

a first method that determines whether two object values are equal; and

a second method that overrides an identity method associated with a superclass of the object by invoking the first method, the identity method for determining the identity of two objects,

wherein the object is locked upon instantiation so that threads fail when attempting to synchronize on the locked object, and wherein each object from the class is automatically locked when that object is instantiated.

23. The object of claim 22, wherein the second method is a final method.

24. The object of claim 22, further comprising:

a third method that returns a hash code for a given object.

25. The object of claim 22, wherein all fields of the object are final.

26. An apparatus for protecting object identity in an object-oriented programming language, comprising:

means for instantiating an object from a first class in memory; and

means for locking the object in response to the instantiating, wherein the identity of the locked object is protected from threads that attempt to synchronize on the locked object, and wherein each object from the first class is automatically locked when that object is instantiated.

27. The apparatus of claim 26, wherein the object includes a first method that determines whether two object values are equal, and a second method that overrides an identity method associated with a superclass of the object by invoking the first method, the identity method for determining the identity of two objects.

28. The apparatus of claim 27, wherein the second method is a final method.

29. The apparatus of claim 27, said means for locking comprising:

means for changing a bit in a header of the object using a thread.

30. The apparatus of claim 29, wherein the thread that changes the bit is a system thread that does not run user code.

31. An apparatus for protecting object identity in an object-oriented programming language, comprising:

means for instantiating an object from a first class in memory, the object including a first method that determines whether two object values are equal, and a second method that overrides an identity method associated with a superclass of the object by invoking the first method, the identity method for determining the identity of two objects; and

means for locking the object in response to the instantiating, wherein the identity of the locked object is protected from threads that attempt to synchronize on the locked object, and wherein each object from the first class is automatically locked when that object is instantiated.

32. The apparatus of claim 31, wherein the second method is a final method.

33. The apparatus of claim 31, wherein the object includes a third method that returns a hash code for a given object.

34. An apparatus for protecting object identity in an object-oriented programming language, comprising:

means for receiving code including an identity operator;

means for invoking an identity method associated with the identity operator;

means for performing a first method, instead of the identity method, based on a determination that the identity method is associated with an object from a first class, the first method for determining whether two object values are equal; and

means for performing an identity function based on a determination that the identity method is not associated with an object from the first class, the identity function for determining whether two object references refer to the same object.

35. The apparatus of claim 34, wherein the identity method associated with the object from the first class is a final method that invokes the first method.

36. The apparatus of claim 34, wherein the object from the first class is locked using a thread upon instantiation in memory so that the identity of the locked object is protected from threads that attempt to synchronize on the locked object.

37. A computer-readable medium containing instructions for performing a process for protecting object identity in an object-oriented programming language, the process comprising:

instantiating an object from a first class in memory, the object including a first method that determines whether two object values are equal, and a second method that overrides an identity method from a superclass of the object by invoking the first method, the identity method for determining the identity of two objects; and

locking the object in response to the instantiating, wherein the identity of the locked object is protected from threads that attempt to synchronize on the locked object, and wherein each object from the first class is automatically locked when that object is instantiated.

38. The computer-readable medium of claim 37, wherein the second method is a final method.

39. The computer-readable medium of claim 37, wherein the object includes a third method that returns a hash code for a given object.

40. The computer-readable medium of claim 37, the locking comprising:

changing a bit in a header of the object using a thread.

41. The computer-readable medium of claim 40, wherein the thread that changes the bit is a system thread that does not run user code.

42. An apparatus for protecting object identity in an object-oriented programming language, comprising:

a memory having a program that;

instantiates an object from a first class in memory, the object including a first method that determines whether two object values are equal, and a second method that overrides an identity method associated with a superclass of the object by invoking the first method, the identity method for determining the identity of two objects; and

locking the object in response to the instantiating, wherein the identity of the locked object is protected from threads that attempt to synchronize on the locked object, and wherein each object from the first class is automatically locked when that object is instantiated; and

a processor that runs the program.

43. An apparatus for protecting object identity in an object-oriented programming language, comprising:

a memory having a program that;

invokes an identity method associated with an identity operator;

performs a first method, instead of the identity method, based on a determination that the identity method is associated with an object from a first class, the first method for determining whether two object values are equal; and

performs an identity function based on a determination that the identity method is not associated with an object from the first class, the identity function for determining whether two object references refer to the same object; and

a processor that runs the program.