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PA165: Service Tier I. Introduction
Petr Adámek

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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
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•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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PA165: Service Tier