Transactional File System in Java – commons transactionAlbert Guo

junyuo@gmail.com

Agenda

CMCS Scenario

Commons Transaction

Commons Transaction Implementation

Conclusion

2

CMCS Scenario

System Architecture

CIS

Green

Windchill

Project Management

Document Management

Change Management

Pro/EWildfire

Pro/E

Wo

rk Sp

ace

Pro/E

PDMLink

Supplier Management

GSM

Product Management

(Part /BOM)

Interface

Ta

ble

SAPERP

ProjectLinkO

DB

C

xmls, files

4

Scenario

5

Commons Transaction

6

Commons Transaction

• http://commons.apache.org/transaction/

7

What is Commons Transaction

① Whenever you have concurrent access to resources and want to protect them with locks, Commons Transaction can be right for you.

② Providing lightweight, standardized, well tested and efficient implementations of utility classes commonly used in transactional Java programming.

③ The 1.x component is compatible to JDK1.2.

8

Commons Transaction Features

Commons Transaction might be useful for you when you

①need transactional file access (i.e. ACID transactions on a set of files)

②have resources that need locking - lock managers can do that for you:

be sure you never forget to release a lock again

let your code have a timer for a whole block of locks

have an out-of-the-box solution for hierarchical locks

plug in your own custom or advanced solutions

9

Commons Transaction Implementation

10

Implementation Steps

11

1. Initialize FileResourceManager

12

2. Initialize FileResourceManager

storeDir String - JavaDoc says: "directory where main data should go after commit".

workDir String - JavaDoc says: directory where transactions store temporary data.

next parameter is a boolean that indicates if the path should be URL encoded. In our example it is false, indicating that we have simple path with no spaces or i18n characters in it.

sLogger LoggerFacade - JavaDoc says: the logger to be used by this store.

13

3. Start FileResourceManager & Start Transaction

14

4. Modify Resources

With the transaction started, you can begin file manipulation. You can perform following operations:

copyResource

createResource

deleteResource

moveResource

writeResource

In our example, we’ll demo createResource and writeResource

15

4. Modify Resources

16

5. Transaction Management

17

Conclusion

18

Conclusion

If you have to operate on files and cannot afford to loose data, seriously consider using commons-transactions package.

It is probably better then any custom mechanism you can come up with. It supports 2 phase commit.

With a little work, you could probably make it into an XA compliant resource.

Src.rar

19