Data persistence is a crucial aspect in software development. It involves storing application data in a persistent storage medium (such as a database) so that the data can be reloaded and used after the program is restarted. Implementing data persistence usually requires writing a lot of code, including database connections, SQL query statements, and data mapping. To simplify this process, Java Persistence API (JPA) came into being.
JPA is a specification on the Java platform that aims to simplify data persistence operations between Java applications and relational databases. It provides an object-relational mapping (ORM) method that allows developers to operate the database in an object-oriented manner without paying attention to the underlying database details.
Using JPA, developers can define the mapping relationship between entity classes and databases through annotations or XML configuration. JPA provides a set of standard annotations, such as @Entity, @Table, @Column, etc., for specifying table names, field names, and various constraints in entity classes. Through these annotations, developers can define relationships between objects in entity classes, such as one-to-one, one-to-many, and many-to-many relationships. In this way, JPA can automatically generate corresponding SQL statements based on these mapping relationships and perform interactive operations with the database.
Here is an example of using JPA for data persistence:
First, we need to introduce the appropriate dependencies. In the Maven project, you can pom.xmladd the following dependencies in the file:
<dependencies>