搞懂Java例外處理的難題：Checked與Unchecked Exceptions不再是問題
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討論Java語言中checked與unchecked exceptions使用上的問題
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搞懂Java例外處理的難題：Checked與Unchecked Exceptions不再是問題
- 1. Teddy Chen teddy@teddysoft.tw Feb. 21 2013
- 3. 系統不穩定 3
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- 7. Problem 7
- 8. Problem 8
- 10. • Correctness – Contract Specification(超出範圍) • Robustness – Exception Handling Copyright@2013 Teddysoft
- 12. Checked Exception Throwable Unchecked Exception Exception Error RuntimeException Copyright@2013 Teddysoft
- 13. declare handle Copyright@2013 Teddysoft
- 16. • Checked exceptions for recoverable conditions – 打死不知道要如何去recover 任何東東？ class FileService { … backup () { FileService fs = new public copy (String s) FileService(); throws IOException { try { … fs.copy(“a.txt”); if (error) } throw new catch (IOException e){ IOException(“reason”); // exception handling code } } } } Copyright@2013 Teddysoft
- 17. 1 2 3 Copyright@2013 Teddysoft
- 18. 1 2 3 Copyright@2013 Teddysoft
- 19. • 我就是不喜歡checked exception，咬我啊! • 例如，Standard Widget Toolkit (SWT, Eclipse的UI元件)只使用unchecked exception： – SWTException用來表示可修復的SWT錯誤。 – SWTError則用來表示不可修復的錯誤。 Copyright@2013 Teddysoft
- 20. Your application Spring DataAccessException unchecked Framework checked Java SQLException HibernateException technology- technology- specific specific Copyright@2013 Teddysoft
- 22. • Exception Type • Recoverability • Application Context • Robustness Level – G1: Error-reporting (錯誤回報） – G2: State-recovery (狀態回復） – G3: Behavior-recovery (行為回復） • Exception Handling Policy Copyright@2013 Teddysoft
- 25. 練習1: 如果Accepter收到一 Message Presentation Layer E'' 5. report 個 IOException，鄉民們第 一個反應是什麼？ AppWin Application E' 4. wrap Layer GameServer Service Layer 3. recover E 2. rethrow 練習2: 如果Accepter收到 Acceptor 一個 RuntimeException， 鄉民們第一個反應是什麼？ JVM E 1. throw Copyright@2013 Teddysoft
- 26. Message 練習3: 如果Accepter收到一 Presentation E'' 5. report 個 IOException，鄉民們該 Layer AppWin 如何處置？ Application E' 4. wrap Layer GameServer 3. recover Service Layer E 2. rethrow 練習4: 如果Accepter收到 Acceptor 一個 RuntimeException， JVM E 1. throw 鄉民們該如何處置？ Copyright@2013 Teddysoft
- 27. Message 練習5: 如果Accepter收到一 Presentation E'' 5. report 個 IOException，鄉民們該 Layer AppWin 如何處置？ Application E' 4. wrap Layer GameServer 3. recover 練習6: 如果GameServer收 Service Layer E 2. rethrow Acceptor 到 IOException ，鄉民們該 如何處置？ JVM E 1. throw Copyright@2013 Teddysoft
- 28. Message Presentation Layer E'' 5. report 練習7: Accepter的RL要 AppWin E' 4. wrap 設為多少？ Application Layer GameServer 3. recover Service Layer E 2. rethrow 練習8: GameServer的RL Acceptor 要設為多少? JVM E 1. throw Copyright@2013 Teddysoft
- 29. Message Presentation Layer E'' 5. report 練習9: Acceptor這一層 AppWin 有哪些policy可用？ Application E' 4. wrap Layer GameServer 3. recover Service Layer E 2. rethrow Acceptor 練習10: GameServer這 JVM 一層有哪些policy可用? E 1. throw Copyright@2013 Teddysoft
- 30. Copyright@2013 Teddysoft 30