System and method for enabling dynamic modifed class reloading in an application server environment

• US 7,882,501 B1
• Filed: 05/01/2000
• Issued: 02/01/2011
• Est. Priority Date: 08/13/1999
• Status: Expired due to Fees

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Oracle America, Inc. (Oracle Corporation)
• Inventors: Soong, Milton, Carlson, Bjorn, Hasani, Santosh
• Primary Examiner(s): DONAGHUE, LARRY D
• Application Number:
  US09/561,697
• Time in Patent Office: 3,928 Days
• Field of Search: 709201-224, 709230-234, 709/312, 709/313, 709/315, 709/318, 709/332, 719310-318, 345/619, 707/1, 707/10, 707/101, 707/103, 717/103, 717120-122, 717162-167, 717168-172
• US Class Current: 717/167
• CPC Class Codes: G06F 8/656 while running
• CPC Class Codes: G06F 9/44521 Dynamic linking or loading; Link editing at or after load time, e.g. Java class loading

Abstract

System and method for enabling dynamic class reloading in an application server environment. A distinction is made between “versionable” and “non-versionable” classes. Versionable classes are classes that should be automatically reloaded when they are modified. The application server(s) may execute a background task that executes periodically to check for modified versionable classes. Users may specify class versionability by specifying a list of explicitly versionable classes, specifying a list of superclasses whose extending classes should be considered to be versionable, and specifying a list of interfaces whose implementing classes should be considered to be versionable. Once the background task discovers a modified versionable class, the background task may cause the class to be reloaded, e.g., by instantiating a new classloader and instructing the new classloader to reload the class. The background task may purge the reloaded class from any caches that the application server maintains.

Claims

1. A method for dynamically reloading classes in an application server environment for an application server, the method comprising:

performing dynamic class reloading while the application server is running without restarting the application server, wherein the dynamic class reloading comprises;

a thread running in the application server environment periodically waking up at intervals;

the thread determining a list of versionable classes, wherein said list of versionable classes comprises a list of classes that should be dynamically reloaded when modified;

the thread determining that a class in the list of versionable classes has been modified since that class was loaded, wherein the thread only checks the classes listed on the list of versionable classes to perform said determining that a class in the list of versionable classes has been modified since that class was loaded; and

the thread reloading the class that was determined to have been modified.

2. The method of claim 1, further comprising:

the thread instantiating a new classloader;

wherein the thread calls the new classloader to perform said reloading the class that was determined to have been modified.

3. The method of claim 1, further comprising:

the thread purging the class that was determined to have been modified from a cache maintained in the application server environment.

4. The method of claim 3, wherein the cache is managed by a component that exposes an interface including a purge method for purging a particular class from the cache;

wherein the thread invokes the purge method to perform said purging the class that was determined to have been modified.

5. The method of claim 1, wherein the application server environment includes a user interface for managing class reloading.

6. The method of claim 5, wherein the user interface enables an administrator to specify the intervals at which the thread wakes up.

7. The method of claim 5, wherein the user interface enables an administrator to specify a list of explicitly versionable classes, wherein the list of explicitly versionable classes comprises names of classes that should be dynamically reloaded when modified;

wherein the list of versionable classes comprises classes listed in the list of explicitly versionable classes.

8. The method of claim 5, wherein the user interface enables an administrator to specify a list of superclasses, wherein the list of superclasses comprises names of classes whose subclasses should be dynamically reloaded when modified;

wherein the list of versionable classes comprises classes that extend the classes listed in the list of superclasses.

9. The method of claim 5, wherein the user interface enables an administrator to specify a list of interfaces, wherein the list of interfaces comprises names of interfaces whose implementing classes should be dynamically reloaded when modified;

wherein the list of versionable classes comprises the implementing classes that implement the interfaces listed in the list of interfaces.

10. The method of claim 1, wherein the list of versionable classes is determined a first time;

wherein the list of versionable classes is re-used each time the thread wakes up.

11. The method of claim 10, wherein the application server environment includes a user interface for managing class reloading;

wherein an administrator uses the user interface to change information specifying which classes should be dynamically reloaded when modified;

wherein, in response to said administrator using the user interface to change information specifying which classes should be dynamically reloaded when modified, the thread re-determines the list of versionable classes.

12. The method of claim 1, wherein information regarding a date of a class file is stored when a class is loaded;

wherein the thread performing said determining that a class in the list of versionable classes has been modified since that class was loaded comprises the thread comparing the date of a class file for that class against the stored information.

13. A system supporting a networked application, the system comprising:

an application server computer system including a CPU and memory;

executable code stored in the memory of the application server computer system, wherein the executable code implements an application server and further implements dynamic class reloading while the application server is running without restarting the application server, wherein the dynamic class reloading comprises a thread that periodically wakes up at intervals;

wherein the thread is executable to determine a list of versionable classes, wherein said list of versionable classes comprises a list of classes that should be dynamically reloaded when modified;

wherein the thread is executable to determine that a class in the list of versionable classes has been modified since that class was loaded, wherein the thread only checks the classes listed on the list of versionable classes to determine that a class in the list of versionable classes has been modified since that class was loaded; and

wherein the thread is executable to reload the class that was determined to have been modified.

14. The system of claim 13, wherein the thread reloading the modified class comprises the thread instantiating a new classloader and instructing the new classloader to reload the class that was determined to have been modified.

15. The system of claim 13, wherein the thread is further executable to purge the class that was determined to have been modified from a cache maintained in the application server environment.

16. The system of claim 15, wherein the cache is managed by a component that exposes an interface including a purge method for purging a particular class from the cache;

wherein the thread invokes the purge method to perform said purging the class that was determined to have been modified.

17. The system of claim 13, further comprising:

executable code implementing a user interface for managing class reloading on the application server computer system.

18. The system of claim 17, wherein the user interface enables an administrator to specify the intervals at which the thread wakes up.

19. The system of claim 17, wherein the user interface enables an administrator to specify a list of explicitly versionable classes, wherein the list of explicitly versionable classes comprises names of classes that should be dynamically reloaded when modified;

wherein the list of versionable classes comprises classes listed in the list of explicitly versionable classes.

20. The system of claim 17, wherein the user interface enables an administrator to specify a list of superclasses, wherein the list of superclasses comprises names of classes whose subclasses should be dynamically reloaded when modified;

wherein the list of versionable classes comprises classes that extend the classes listed in the list of superclasses.

21. The system of claim 17, wherein the user interface enables an administrator to specify a list of interfaces, wherein the list of interfaces comprises names of interfaces whose implementing classes should be dynamically reloaded when modified;

wherein the list of versionable classes comprises the implementing classes that implement the interfaces listed in the list of interfaces.

22. The system of claim 13, wherein the list of versionable classes is determined a first time;

wherein the list of versionable classes is re-used each time the thread wakes up.

23. The system of claim 22, further comprising:

executable code implementing a user interface for managing class reloading on the application server computer system;

wherein an administrator uses the user interface to change information specifying which classes should be dynamically reloaded when modified;

wherein, in response to said administrator using the user interface to change information specifying which classes should be dynamically reloaded when modified, the thread is executable to re-determine the list of versionable classes.

24. The system of claim 13, wherein information regarding a date of a class file is stored when a class is loaded;

wherein to determine that a class in the list of versionable classes has been modified since that class was loaded, the thread is configured to compare the date of a class file for that class against the stored information.

25. A non-transitory computer-readable storage medium storing program instructions, which when executed:

perform dynamic class reloading while an application server is running without restarting the application server, wherein the dynamic class reloading is operable to;

cause a thread to periodically wake up at intervals;

wherein the thread is executable to determine a list of versionable classes, wherein said list of versionable classes comprises a list of classes that should be dynamically reloaded when modified;

wherein the thread is executable to determine that a class in the list of versionable classes has been modified since that class was loaded, wherein the thread only checks the classes listed on the list of versionable classes to determine that a class in the list of versionable classes has been modified since that class was loaded;

wherein the thread is executable to reload the class that was determined to have been modified.

26. The non-transitory computer-readable storage medium of claim 25, wherein the thread reloading the class that was determined to have been modified comprises the thread instantiating a new classloader and instructing the new classloader to reload the class that was determined to have been modified.

27. The non-transitory computer-readable storage medium of claim 25, wherein the thread is further executable to perform purging the class that was determined to have been modified from a cache maintained in an application server environment for the application server.

28. The non-transitory computer-readable storage medium of claim 27, wherein the cache is managed by a component that exposes an interface including a purge method for purging a particular class from the cache;

wherein the thread invokes the purge method to perform said purging the class that was determined to have been modified.

29. The non-transitory computer-readable storage medium of claim 25, further comprising:

program instructions operable to implement a user interface for managing class reloading.

30. The non-transitory computer-readable storage medium of claim 29, wherein the user interface enables an administrator to specify the intervals at which the thread wakes up.

31. The non-transitory computer-readable storage medium of claim 29, wherein the user interface enables an administrator to specify a list of explicitly versionable classes, wherein the list of explicitly versionable classes comprises names of classes that should be dynamically reloaded when modified;

wherein the list of versionable classes comprises classes listed in the list of explicitly versionable classes.

32. The non-transitory computer-readable storage medium of claim 29, wherein the user interface enables an administrator to specify a list of superclasses, wherein the list of superclasses comprises names of classes whose subclasses should be dynamically reloaded when modified;

wherein the list of versionable classes comprises classes that extend the classes listed in the list of superclasses.

33. The non-transitory computer-readable storage medium of claim 29, wherein the user interface enables an administrator to specify a list of interfaces, wherein the list of interfaces comprises names of interfaces whose implementing classes should be dynamically reloaded when modified;

wherein the list of versionable classes comprises the implementing classes that implement the interfaces listed in the list of interfaces.

34. The non-transitory computer-readable storage medium of claim 25, wherein the list of versionable classes is determined a first time;

wherein the list of versionable classes is reused each time the thread wakes up.

35. The computer-readable storage medium of claim 34, further comprising:

program instructions operable to implement a user interface for managing class reloading;

wherein an administrator uses the user interface to change information specifying which classes should be dynamically reloaded when modified;

wherein, in response to said administrator using the user interface to change information specifying which classes should be dynamically reloaded when modified, the thread is executable to re-determine the list of versionable classes.

36. The non-transitory computer-readable storage medium of claim 25, wherein information regarding a date of a class file is stored when a class is loaded;

wherein to determine that a class in the list of versionable classes has been modified since that class was loaded, the thread is further executable to compare the date of a class file for the class that was determined to have been modified against the stored information.