System and method for handling threads of execution

• US 6,711,739 B1
• Filed: 11/08/1999
• Issued: 03/23/2004
• Est. Priority Date: 11/08/1999
• Status: Expired due to Fees

• Current Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Kutcher, Jeffrey M.
• Primary Examiner(s): Grant, William
• Assistant Examiner(s): Ali, Syed J
• Application Number:
  US09/436,792
• Time in Patent Office: 1,597 Days
• Field of Search: 709/1-108, 717/100, 717/114, 717/116, 717/118, 717/120, 717/121, 717/123
• US Class Current: 718/1
• CPC Class Codes: G06F 9/4488 Object-oriented
• CPC Class Codes: G06F 9/4843 by program, e.g. task dispatcher, supervisor, operating system

Abstract

A mechanism for controlling threads in a Java application while avoiding the unsafe conditions inherent in the use of existing java.lang.Thread methods. In one embodiment, a first class is defined for handling threads in an application. The first class uses a target variable to indicate whether a thread should continue to run, or whether it should be stopped. This first class provides a start( ) method to set up the target variable, a stop( ) method to set the target variable to indicate that the thread should be stopped, and an abstract run( ) method. The functionality of the run( ) method is provided by one or more additional classes which extend the first class. The additional classes override the abstract run( ) method and define the tasks to be performed by threaded objects instantiated from these classes. When a thread needs to be stopped, the corresponding target variable is set to indicate that it should be stopped. The thread periodically checks the target variable and, when the target variable is set to indicate that the thread should be stopped, the thread executes one or more instructions that cause execution of the thread to complete and to exit normally.

Claims

1. A system, comprising:

a dedicated Java thread handler class which includes;

a start method that sets a target variable to indicate that a thread extending said dedicated Java thread handler class is running;

an abstract run method; and

a stop method that sets said target variable to indicate that said thread extending said Java class is to be stopped;

wherein said dedicated Java thread handler class is configured to be extended by custom thread subclasses that each includes a run method that overrides said abstract run method of said Java class, wherein said dedicated Java thread handler class does not include functionality particular to any of the custom thread subclasses, wherein said run method of one of the custom thread subclasses;

provides one or more instructions to be executed within said thread, wherein said instructions are configured to access one or more objects during execution of said thread;

provides one or more checks during execution of said thread to determine if said target variable indicates that said thread is to be stopped; and

completes execution of said run method if one of the one or more checks determines that said thread is to be stopped;

wherein completing execution of said run method if one of the one or more checks determines that said thread is to be stopped stops the thread without throwing an exception and leaves each of said one or more objects in a consistent state.

2. The system of claim 1, wherein said dedicated Java thread handler class implements the Java Runnable interface, and wherein an object instantiated from said Java class is configured to invoke methods defined by said Runnable interface.

3. The system of claim 1, wherein said dedicated Java thread handler class defines an additional method, wherein said additional method returns “

true”

if a corresponding thread is running and “

false”

if said corresponding thread is to be stopped.

4. The system of claim 3, wherein said one or more checks access said additional method to determine if said thread is to be stopped.

5. The system of claim 1, wherein said target variable is settable by the ran method to indicate that said thread is to be stopped.

6. The system of claim 1, wherein said target variable is settable by other threads to indicate that said thread is to be stopped.

7. The system of claim 1, wherein said dedicated Java thread handler class is configured to be extended to generate one or more subclasses in a plurality of Java applications, wherein each of said one or more subclasses in each of the plurality of Java applications is configured to be instantiated as one or more objects in the Java application, and wherein the one or more objects are configured to be executed as threads of the Java application.

8. The system of claim 1, wherein each of the threads of the Java application is configured to leave the Java application in a known state after termination of execution of the thread.

9. A method, comprising:

defining a dedicated Java thread handler class wherein said dedicated Java thread handler class defines a first method that initializes a target variable to indicate that a thread extending said dedicated Java thread handler class is running, wherein said dedicated Java thread handler class defines a second method that sets said target variable to indicate that said thread extending said dedicated Java thread handler class is to be stopped;

instantiating an object that inherits said methods from said dedicated Java thread handler class, wherein said object includes a run method implementing one or more instructions to perform a particular task, wherein is said dedicated Java thread handler class does not include any instructions for said particular task;

creating a custom thread in which said one or more instructions are executed;

starting said custom thread;

calling said first method to initialize said target variable;

initiating execution of said run method in said custom thread;

calling said second method during execution of said run method to indicate that said custom thread is to be stopped;

said run method detecting that said target variable is set to indicate that said custom thread is to stopped; and

completing execution of said run method after said detecting;

wherein said completing execution of said run method stops the custom thread without throwing an exception and leaves one or more objects accessed by the custom thread in a consistent state.

10. The method of claim 9, wherein said dedicated Java thread handler class implements the Java Runnable interface.

11. The method of claim 9, wherein said dedicated Java thread handler class defines an additional method, wherein said additional method returns “

true”

if a corresponding thread is running and “

false”

if said corresponding thread is to be stopped.

12. The method of claim 11, wherein said run method detecting that said target variable is set to indicate that said custom thread is to be stopped comprises accessing said additional method to determine if said custom thread is to be stopped.

13. A computer-readable storage medium containing a plurality of program instructions, wherein said program instructions define a method comprising:

defining a dedicated Java thread handler class wherein said dedicated Java thread handler class defines a first method that initializes a target variable to indicate that a thread extending said dedicated Java thread handler class is running, wherein said dedicated Java thread handler class defines a second method that sets said target variable to indicate that said thread extending said dedicated Java thread handler class is to be stopped;

instantiating an object that inherits said methods from said dedicated Java thread handler class, wherein said object includes a run method implementing one or more instructions to perform a particular task, wherein is said dedicated Java thread handler class does not include any instructions for said particular task;

creating a custom thread in which said one or more instructions are executed;

starting said custom thread;

calling said first method to initialize said target variable;

initiating execution of said run method in said custom thread;

calling said second method during execution of said run method to indicate that said custom thread is to be stopped;

said run method detecting that said target variable is set to indicate that said custom thread is to be stopped; and

completing execution of said run method after said detecting;

wherein said completing execution of said run method stops the custom thread without throwing an exception and leaves one or more objects accessed by the custom thread in a consistent state.

14. The storage medium of claim 13, wherein said dedicated Java thread handler class implements the Java Runnable interface.

15. The storage medium of claim 13, wherein said dedicated Java thread handler class defines an additional method, wherein said additional method returns “

true”

if a corresponding thread is running and “

false”

if said corresponding thread is to be stopped.

16. The storage medium of claim 15, wherein said run method detecting that said target variable is set to indicate that said custom thread is to be stopped comprises accessing said additional method to determine if said custom thread is to be stopped.

17. A system, comprising:

a dedicated Java thread handler class which includes;

a start method that sets a target variable to indicate that threads extending said dedicated Java thread handler class are running,

an abstract run method, and

a stop method that sets said target variable to indicate that said threads extending said Java class am to be terminated;

wherein said dedicated Java thread handler class is configured to be extended by custom thread subclasses each including a run method that overrides said abstract run method, wherein said dedicated Java thread handler class does not include functionality particular to any of the custom thread subclasses, wherein each run method provides code to be executed by a thread implementing a particular one of the subclasses including said run method; and

wherein, during execution of said thread, if said target variable is set to indicate that said thread is to be terminated, said run method is configured to complete execution to terminate the thread normally.

18. The system of claim 17, wherein, to terminate the thread normally, no exceptions are thrown and one or more objects accessed by said thread are left in a consistent state.

19. The system of claim 17, wherein, to terminate the thread normally, a Java application in which the thread is configured to execute is left in a known state.

20. The system of claim 17, wherein said dedicated Java thread handler class is configured to be extended to generate subclasses in a plurality of Java applications, wherein each of said subclasses in each of the plurality of Java applications is configured to be instantiated as one or more objects in the Java application, and wherein the one or more objects are configured to be executed as threads of the Java application.

21. The system of claim 20, wherein each of the threads of the Java application is configured to leave the Java application in a known state after termination of execution of the thread.

22. The system of claim 17, wherein said dedicated Java thread handler class implements the Java Runnable interface and wherein objects instantiated from said subclass are configured to invoke methods defined by said Runnable interface.

23. A method, comprising:

starting execution of a custom thread which implements a subclass of a dedicated Java thread handler class, wherein said dedicated Java thread handler class includes a start method that initializes a target variable to indicate that said custom thread is running and a stop method that sets said target variable to indicate that said custom thread is to be stopped, and wherein said subclass includes a run method that includes code executed by said custom thread, wherein the thread handler class does not include functionality particular to the custom thread;

calling said stop method during execution of said custom thread to indicate that said custom thread is to be stopped;

said run method detecting that said target variable is set to indicate that said custom thread is to be stopped; and

completing execution of said run method after said detecting;

wherein said completing execution of said run method after said detecting stops the custom thread without throwing an exception and leaves objects accessed by the custom thread in a consistent state.

24. The method of claim 23, wherein said dedicated Java thread handler class implements the Java Runnable interface, and wherein an object instantiated from said subclass is configured to invoke methods defined by said Runnable interface.