The application principle and practice of the Spring ORM framework in the Java library
The application principle and practice of the Spring ORM framework in the Java library
Overview:
Spring ORM is an important module in the Spring framework to simplify the interaction between Java applications and relational databases.It provides developers with simple and flexible ways to access and operate databases, and at the same time, it can maintain efficient performance without significantly reduced the amount of code.This article will introduce the application principles and practice of Spring ORM, and provide some Java code examples.
1. The application principle of Spring ORM
Spring ORM is implemented based on the persistent framework such as Java's persistence API (JPA) and Hibernate. It has greatly simplified the application process of the application by separating transaction management and database access logic and business logic.
1. Data source configuration:
First, you need to define the data source in the Spring configuration file, which includes information such as the connection of the database and the user name and password.You can use the built -in data source provided by Spring, such as BasicdataSource, or you can customize the data source.
2. Configure the physical class:
Next, you need to define the physical class corresponding to the database table in the application.These physical classes use JPA annotations (such as@Entity,@Table,@ID, etc.) to indicate the mapping relationship between them and the database table.
3. Configure persistence unit:
Spring ORM uses Persistence Unit to manage the mapping between the physical class and the database.The persistent unit consists of one or more physical classes, and each persistence unit has a unique name for reference in the application.You can configure or use the XML configuration by configure or use the XML configuration by configuration units in the Spring configuration file.
4. Configure EntityManagerFactory:
EntityManagerFactory is a factory class used to create and manage the EntityManager instance that creates and manage the entity class.Configure EntityManagerFactory to specify the name, data source and other information of the persistent unit.
5. Arrangement TransactionManager:
Affairs management is one of the key functions of Spring ORM.Spring provides a variety of transaction management strategies, such as annotated transactions, XML -based declarations.The transaction manager is responsible for connecting the transaction with the database operation and ensuring that the database changes are properly handled when the transaction is completed or rolled back.
6. Define data access objects (DAO):
The data access object is the core component of Spring ORM, which is used to encapsulate the access operation of the database.You can use @Repository annotations to identify DAO and use @Autowired annotations to inject them into other components.
7. Inject EntityManager:
In DAO, the EntityManager is injected into DAO member variables by using @PerstenceContext annotations.EntityManager is the core interface of JPA and is used to perform interactive operations with databases.
8. Write data access method:
Finally, write a data access method in DAO.You can use the query language (JPQL) or Native SQL provided by JPA to perform the database query. You can also use the CRUD method provided by the EntityManager to perform additional, deletion and modification inspection operations.
2. Spring ORM's practice example
The following is a simple example that demonstrates how to use Spring ORM to access the database.
1. Define the physical class:
@Entity
@Table(name = "users")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@Column(name = "name")
private String name;
// omit the getter and setter method
}
2. Configure persistent unit:
<persistence-unit name="myPersistenceUnit" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<properties>
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/mydb"/>
<property name="javax.persistence.jdbc.user" value="root"/>
<property name="javax.persistence.jdbc.password" value="password"/>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
</properties>
</persistence-unit>
3. PlanSactionManager:
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory"/>
</bean>
4. Define data access interface:
@Repository
public interface UserDao extends JpaRepository<User, Long> {
User findByName(String name);
}
5. Inject EntityManager:
@Repository
public class UserDaoImpl implements UserDao {
@PersistenceContext
private EntityManager entityManager;
// omit other methods
}
6. Writing business logic code:
@Service
public class UserService {
@Autowired
private UserDao userDao;
public User getUserByName(String name) {
return userDao.findByName(name);
}
}
Through the above examples, we can see the application principles and practical processes of Spring Orem.By configured data sources, physical classes, persistent units and transaction managers, we can easily realize the seamless interaction between Java applications and databases.
