JPA CRUD operation

JPA is a Java specification for Object-Relational Mapping (ORM). It provides a standard way to move Java objects to a related database table. CRUD operations are basic operations used to interact with data in a database. In JPA, these operations are performed on entities that are Java objects that represent data stored in the database.

Create Operation:

The Create operation involves inserting new records into the database. In JPA, this is achieved by the persisting new entity instances.

Steps to implement the create operation:

• Create a new instance of the entity class
• Set the values for its attributes.
• Use the EntityManagers persist() method to make entity managed and persistent.

Example:

EntityManager em = entityManagerFactory.createEntityManager();
EntityTransaction transaction = em.getTransaction();
transaction.begin();
//create the instance of the entity
Employee employee = new Employee();
//set the attributes
employee.setName("John");
employee.setSalary(50000);
em.persist(employee);
transaction.commit();

Read Operation:

The read operation involves the retrieving the existing records from the database. In JPA, this is the typically done using primary keys of the entity.

Steps to implement :

• Use the EntityManagers find() method to the retrieve the entity by its primary key.

Example:

Employee employee = em.find(Employee.class, 1L);

Update Operation:

The update operation involves modifying the existing records in the database. In JPA, this is the accomplished by the updating managed by the entity instances.

Steps to implement:

• Retrieve the entity using Entitymanagers find() method or the query.
• Modify the arrtibutes of the entity.
• Use the EntityManagers merge() method to the update the entity in database.

Example:

Employee employee = em.find(Employee.class, 1L);
employee.setSalary(55000);
em.merge(employee);

Delete Operation:

The delete operation involves removing records from the database. In JPA, this can be done by removing the managed entity instances.

Steps to implement:

• Retrieve the entity using the EntityManagers find() method or the query.
• Use the EntityManagers remove() method to the delete entity from the database.

Example:

Employee employee = em.find(Employee.class, 1L);
em.remove(employee);

In the JPA, these CRUD operations are typically performed within the transaction to the ensure data consistency and integrity. Transaction Management can be handled by the EntityManager which begins, commit or the rolls back transactions as necessary.

JPA in Java can be called Java Persistence API (JPA) which can simplify the process of working with the database by providing object relationship mapping structure CRUD operations (Create, Read, Update, Delete) are actions especially if it contains database abuse.