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Transactional File System in Java – commons transactionAlbert Guo
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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