Chapter 5: Spring Data JPA, Hibernate & Database

Mastering enterprise persistence requires understanding JPA lifecycle states, relationship mapping best practices, query method derivation, eliminating N+1 performance bottlenecks, declarative transactions, and Flyway schema versioning.

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🧭 Subtopics & Curriculum

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ORM Foundations5.1

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5.1 JPA & Hibernate Fundamentals

• 1. The Stack: JDBC vs JPA vs Hibernate vs Spring Data
• 2. The 4 JPA Entity Lifecycle States
• 3. The First-Level Cache & Dirty Checking

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Associations & Schema5.2

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5.2 Entity Mappings & Relationships

• @Entity
• @Table
• @Id
• @GeneratedValue
• Core Mapping Annotations
• Column Mapping
  • nullable
  • unique
  • length
  • @Transient
• Association Multiplicities & Ownership
  • The Rule of Ownership:
  • One-to-Many / Many-to-One (Bidirectional Best Practice)
• FetchType: LAZY vs EAGER

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Data Access Layer5.3

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5.3 Repositories & Query Methods

• Spring Data Repository Hierarchy
• Repository
  • Common JPA Repository Methods
• What is JpaRepository?
• 2. Derived Query Method Keywords
• 3. Custom @Query (JPQL vs Native SQL)
• 4. Pagination & Sorting

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Query Tuning5.4

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5.4 N+1 Problem & Optimization

• 1. How the N+1 Problem Manifests
• 2. Solution 1: JOIN FETCH in JPQL
• 3. Solution 2: @EntityGraph
• 4. Solution 3: DTO Projections (Zero Overhead)
  • Benefits of DTO Projections:

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ACID Guarantees5.5

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5.5 Transaction Management

• 1. Transaction Propagation Behaviors
  • Practical Use Case for REQUIRES_NEW:
• 2. Transaction Isolation Levels
• 3. Rollback Rules & Read-Only Optimization
  • Default Rollback Policy:
  • Read-Only Optimization:

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Schema Versioning5.6

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5.6 Database Migrations with Flyway

• 1. Why Dedicated Migration Tools?
• 2. Flyway Migration File Naming Rules
• 3. Migration Example & Production Configuration
  • Migration File: src/main/resources/db/migration/V1__init_schema.sql
  • application.yml Production Configuration:
  • The flyway_schema_history Table

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