Transactional File System in Java – commons transaction

Transactional File System in Java – commons transactionAlbert Guo

jguo@ptc.com

Agenda

Use Case

Commons Transaction

Commons Transaction Implementation

Conclusion

Appendix

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Commons Commons IOIO

Commons Commons LangLang

Commons Commons TransactionTransaction

Use Case

Use Case

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Commons Commons IOIO

Commons Commons LangLang

Commons Commons TransactionTransaction

Commons Transaction

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Commons Transaction

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

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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.

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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

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Commons Transaction Implementation

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Implementation Steps

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1. Initialize FileResourceManager

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•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.

•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.

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2. Start FileResourceManager / 3. Start Transaction

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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

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4. Modify Resources

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5. Transaction Management

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Conclusion

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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

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Appendix

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Appendix

Commons Transaction

– Aimed at providing lightweight, standardized, well tested and efficient implementations of utility classes commonly used in transactional Java programming. Initially there were implementations for multi level locks, transactional collections and transactional file access. The 1.x component is compatible to JDK1.2.

Commons IO

– Commons IO is a library of utilities to assist with developing IO functionality.

Commons Lang

– The Lang Component provides a host of helper utilities for the java.lang API, notably String manipulation methods, basic numerical methods, object reflection, creation and serialization, and System properties.

Log4j

– log4j is a Java-based logging utility. It was originally written by Ceki Gülcü and is now a project of the Apache Software Foundation. It is used primarily as a debugging tool.

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