tailieunhanh - Transaction & Security

Chuyên đề Lập trình Java & J2EE Chương 16 Biên soạn: Nguyễn văn Lành | Transaction & Security Chuyên đề Lập trình Java & J2EE Chương 16 Biên soạn: Nguyễn văn Lành Motivation for Transactions Atomic Operations Recovery after Network or Machine Failure Multiple Users Sharing Data avoid those problems by properly using transactions. The ACID Properties Atomicity guarantees that many operations are bundled together and appear as one contiguous unit of work. Consistency guarantees that a transaction leaves the system’s state to be consistent after a transaction completes. Isolation protects concurrently executing transactions from seeing each other’s incomplete results. Durability guarantees that updates to managed resources, such as database records, survive failures. Transactional Models Flat transaction is a series of operations that are performed atomically as a single unit of work. Nested transaction allows to embed atomic units of work within other units of work. Transsaction demarcation Programmatic Transactions you are responsible for issuing a . | Transaction & Security Chuyên đề Lập trình Java & J2EE Chương 16 Biên soạn: Nguyễn văn Lành Motivation for Transactions Atomic Operations Recovery after Network or Machine Failure Multiple Users Sharing Data avoid those problems by properly using transactions. The ACID Properties Atomicity guarantees that many operations are bundled together and appear as one contiguous unit of work. Consistency guarantees that a transaction leaves the system’s state to be consistent after a transaction completes. Isolation protects concurrently executing transactions from seeing each other’s incomplete results. Durability guarantees that updates to managed resources, such as database records, survive failures. Transactional Models Flat transaction is a series of operations that are performed atomically as a single unit of work. Nested transaction allows to embed atomic units of work within other units of work. Transsaction demarcation Programmatic Transactions you are responsible for issuing a begin statement and either a commit or an rollback statement BMT: do not alow for Entity bean Declarative Transactions Specify transaction attributes in deployment descriptor Container automatically handle transactional issues CMT Client-Initiated Transactions Transaction attribute Required RequiresNew Supports Mandatory Never NotSupported Required Requires New Mandatory Never Bean Managed Transaction Java Transaction API (JTA) JTA can be used in client & bean code to programmatically control transactional boundaries. The interface you use to programmatically control transactions is . UserTransaction interface Code sample Transactional Isolation Concurrency Control locking on the database to prevent the two components from reading data Four transaction isolation levels: READ UNCOMMITTED does not offer any isolation guarantees (dirty read) but offers the highest performance. READ COMMITTED REPEATABLE READ SERIALIZABLE: Use SERIALIZABLE for .

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