Jakarta Persistence API data duration operation details

Jakarta Persistence API (JPA) is a data persistence framework for Java applications, which provides a set of APIs for manipulating and operating databases.In this article, we will introduce the durable operation of JPA in detail and provide some Java code examples. The durable operation in JPA mainly involves the following aspects: the preservation, update, deletion and query of entities (Entity).We will explain one by one. 1. Entity Persistence The entity refers to the Java object corresponding to the table in the database.In JPA, the preservation of the entity is very simple. Just use the Persist () method of EntityManager to save the physical object into the database.The following is a sample code that preserves the entity: EntityManager EntityManager = ... // Get the EntityManager object EntityTransaction transaction = entityManager.getTransaction(); transaction.begin(); // Create a new physical object User user = new User(); user.setName("John"); user.setEmail("john@example.com"); // Save the physical object to the database entityManager.persist(user); transaction.commit(); 2. Entity Update The physical update refers to modifying the entity objects that already exist in the database.In JPA, we can use the Merge () method of EntityManager to save the modified physical objects back back to the database.The following is an example code for physical updates: EntityManager EntityManager = ... // Get the EntityManager object EntityTransaction transaction = entityManager.getTransaction(); transaction.begin(); // Query the physical object to be updated User user = entityManager.find(User.class, 1L); // Update the attributes of the physical object user.setName("Updated Name"); user.setEmail("updated@example.com"); // Save the modified physical object to the database entityManager.merge(user); transaction.commit(); 3. Entity DeleTion The deletion of entity refers to deleting an existing entity object from the database.In JPA, we can use the REMOVE () method of EntityManager to perform the deletion operation.Here are a sample code for physical deletion: EntityManager EntityManager = ... // Get the EntityManager object EntityTransaction transaction = entityManager.getTransaction(); transaction.begin(); // Query the physical object to be deleted User user = entityManager.find(User.class, 1L); // Delete the physical object entityManager.remove(user); transaction.commit(); 4. Entity Query Sports queries refer to the physical object from the database.In JPA, we can use the query language (JPQL) to perform various types of query operations.The following is a simple physical query example code: EntityManager EntityManager = ... // Get the EntityManager object // Create query Query query = entityManager.createQuery("SELECT u FROM User u WHERE u.name = :name"); // Set the query parameter query.setParameter("name", "John"); // Execute the query and get the query results List<User> users = query.getResultList(); // Traversing query results for (User user : users) { System.out.println("Name: " + user.getName() + ", Email: " + user.getEmail()); } The above is the basic aspect of the durable operation of data in JPA.In addition, JPA also provides high -level characteristics such as more complex query functions, transaction management, and associated relationships, which can meet various complex data persistence needs. I hope this article can help you better understand the durable operation of JPA's data.If you are interested in JPA, you can further learn the other characteristics and usage of JPA.