Spring Boot Tutorial 0/110 lessons ~6 min read Lesson 27“Production-grade backends”

Spring Data JPA

Spring Data JPA turns repository interfaces into runtime implementations.

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Focus

3 guided sections

Practice signal

Examples included

Career prep

Foundation builder

Introduction

Spring Data JPA turns repository interfaces into runtime implementations. You declare what you need; Spring generates the SQL. JpaRepository<Entity, Id> ships with 15+ methods for free.

Informative example

public interface OrderRepository extends JpaRepository<Order, Long> {

  // Derived query — Spring builds the SQL from the method name
  List<Order> findByUserIdAndStatusOrderByCreatedAtDesc(Long userId, OrderStatus status);

  // Pagination
  Page<Order> findByStatus(OrderStatus status, Pageable pageable);

  // Projection (only load what you need)
  @Query("select new com.acme.OrderSummary(o.id, o.status, o.totalCents) from Order o where o.userId = :uid")
  List<OrderSummary> summariesFor(@Param("uid") Long uid);

  // Aggregate
  @Query("select count(o) from Order o where o.status = ?1")
  long countByStatus(OrderStatus status);
}

Best practices

Method names work great for ≤3 conditions; beyond that use @Query JPQL.
Always paginate list endpoints — never findAll() in prod.
Use projections for read-heavy endpoints — load 3 columns, not 30.

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