Master the common data persistence operation method in the "Persistence API" framework

Master the common data persistence operation method in the "Persistence API" framework introduction: Data persistence is one of the common tasks in applications. It helps us store data in a reliable manner in a database, such as in a database.In order to simplify the data persistence, Java provides a framework called "Persistence API" (referred to as JPA).In this article, we will discuss the durable operation methods commonly used in the JPA framework and provide some Java code examples. JPA Introduction: Java Persistence API (JPA) is a Java standard to describe the mapping between objects and relational databases.JPA provides a set of interfaces and classes for processing data persistent operations, enabling developers to perform database operations through simple Java syntax without writing too much SQL statement. Common data persistence operation methods: 1. Create a physical class In JPA, we need to create a physical class representing the database table.The physical class uses annotations to specify information such as table names, field names and associations.The following is an example: @Entity @Table(name = "users") public class User { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @Column(name = "name") private String name; // Getters and setters } 2. Create persistent units The persistent unit is a configuration unit to describe the mapping relationship between the data source and the physical class.In JPA, we can use XML or annotation to define persistent units.The following is an example of the persistence unit using annotation definition: @PersistenceUnit(unitName = "MyPersistenceUnit") public class DatabaseManager { // ... } 3. Create a physical manager factory The entity manager factory is used to create a physical manager, which is the main entrance point for persistent operations.We can obtain the physical manager through a physical manager factory to perform the durable operation of data.The following is an example: EntityManagerFactory emf = Persistence.createEntityManagerFactory("MyPersistenceUnit"); EntityManager em = emf.createEntityManager(); 4. Insert data To insert data, we can use the `Persist () method of a physical manager to save a new physical object.The following is an example: User user = new User(); user.setName("John Doe"); em.getTransaction().begin(); em.persist(user); em.getTransaction().commit(); 5. Query data JPA provides a wealth of query language, such as using JPQL (Java Persistence Query Language) for query.The following is an example: TypedQuery<User> query = em.createQuery("SELECT u FROM User u WHERE u.name = :name", User.class); query.setParameter("name", "John Doe"); List<User> users = query.getResultList(); 6. Update and delete data We can use the `Merge ()` method of the physical manager to update the physical data and use the `Remove ()` method to delete the entity.The following is an example: User user = em.find(User.class, 1L); user.setName("Jane Smith"); em.getTransaction().begin(); em.merge(user); em.getTransaction().commit(); em.getTransaction().begin(); em.remove(user); em.getTransaction().commit(); in conclusion: By using the JPA framework, we can simplify data persistent operations.This article introduces common data durable methods in the JPA framework, including creating physical class, creating persistent units, creating a physical manager factories, inserting data, querying data, and updating and deleting data.I hope this article will help you understand the JPA framework and master the data persistent operation method. Reference materials: - Java Persistence API (JPA) - https://javaee.github.io/javaee-spec/javadocs/javax/persistence/package-summary.html