Hibernate / JPA (1)

Hibernate / JPA and JDBC

• Hibernate / JPA uses JDBC for all database communications

💎 Object-To-Relational Mapping(ORM)

• The developer defines mapping between Java class and database table

💎 What is JPA?

• Jakarta Persistence API
  - Standard API for ORM
• Only a specification
  - Defines a set of interfaces
  • 사용하기 위해서는 구현체가 필요하다.

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⚾ Saving a Java Object with JPA

// create Java Object
Student theStudent = new Student("abc, "xyz");

// save it to database
entityManager.persist(theStudent);

1. entityManager: Special JPA helper object
2. .persist: The data will be stored in the database SQL insert

⚾ Retrieving a Java Object with JPA

// now retreive from database using the primary key
int theId = 1;
Student myStudent = entityManager.find(Student.class, theID);

1. find: Query the database for given id or the pK

⚾ Querying for Java Objects

// gives a list of all of those student objects
TypedQuery<Student> theQuery = entityManager.createQuery("from student", Student.class);

List<Student> students = theQuery.getResultList();

1. getResultList(): Returns a list of Student Objects from the database