PA165: Service Tier I.
Introduction
Petr Adámek
Content: Service Tier
• Basic Concepts
– Component lifecycle and configuration, IoC
– AOP, Interceptors
• Architecture of Application Tier
– Overview
– DAO, Services, Service Façade, Adapters
• Transaction Management
– Where and How control transactions
– Local vs. Global Transactions
– JTA
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BASIC CONCEPTS
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Components Lifecycle
• We need to control component lifecycle and configuration
• Possible approaches
– Hardcoded
– Controlled by some container
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Component Configuration
• Components needs some resources (other components, data
sources, etc.) and configuration
• Configured statically
– Hardcoded
• Configured dynamically at runtime (IoC)
– Lookup
• JNDI
• ServiceLoader
• NetBeans Lookup
– IoC
• Configured by anotations
• Configured by XML descriptor
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AOP
• We often need to include some aspects that affects lots of our
application parts
– Transaction management
– Authorization
– Validation
– Logging or auditing
– Exception handling or translation
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AOP
• Template method
– OOP approach
– You need new class for each operation
• AOP/Interceptors
– Incompatible with pure OOP
– More practical
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ARCHITECTURE
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Architecture Design Patterns
• DAO
• Service Façade
• Adapter
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TRANSACTION MANAGEMENT
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Local vs. Global Transactions
• Local transactions
– Controlled by API of given low-level technology
– Depend on given technology
• Global transactions
– Controlled independently on persistent technology
– Allows to include more operations into single transaction
– Distributed Transaction support (transaction could include operations
on different databases or other transactional resources)
– JTA
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Transactions and threads
• Problem with the scope of the transaction
– Different requests must be processed in different transactions (we
can’t share transaction between threads)
– One transaction includes more operations in different components
(we can’t create new transaction for each operation)
• Solution
– Transaction is bound to thread
– EntityManager proxy, ThreadLocal variable
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Transactions Control
• Usually global transactions
• Usually declarative approach
• Usually on Service Façade or Adapter level
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Questions
?
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