Discussion on the technical principles of the persistent API framework in the Java class library
Discussion on the technical principles of the persistent API framework in the Java class library
introduction:
Persistence means that the data is stored in a certain medium, so that the data is still available after different execution processes or system restart.The persistent API framework in the Java library provides a flexible and reliable way to manage the durability of data.This article will explore the technical principles of the persistent API framework in the Java library and provide related programming code and configuration.
1. What is the persistent API framework?
The persistent API framework is a set of libraries and tools to simplify the process of database access and data persistence.They provide a high -level abstraction that allows developers to process data in an object without having to care about the details of the bottom database.
2. Technical principles of persistent API framework
The technical principles of the persistent API framework involve the following aspects:
2.1 Object Relationship Map (ORM):
The persistence API framework maps the Java object with the underlying database table through ORM technology.They use metadata to describe the mapping relationship between the object and the table, including the relationship between the attributes of the object and the relationship between the corresponding table, and the relationship between the object.ORM technology allows developers to directly operate Java objects without manually writing SQL statements for database operations.
2.2 Database connection management:
The persistence API framework is responsible for the management of the connection with the database.They provide connection pools to reuse the database connection resources to reduce the creation and destruction of the connection.The connection pool can dynamically adjust the number of connections according to the application of the application to improve the performance and scalability of the system.
2.3 transaction management:
The persistent API framework provides transaction management functions to ensure that the operation of the database is either successfully submitted or rolled back.They use the transaction manager to monitor the beginning, submission and rollback of the transaction, and deal with the problems of concurrent access and resource conflict to ensure the consistency and integrity of the data.
2.4 Caches Management:
The persistent API framework usually uses cache to improve the reading performance of data.They will slowly query the results in the memory to avoid repeated query databases.The cache can be configured according to application requirements, such as using LRU (recently used) strategies to eliminate unused data to save memory use.
2.5 Query Language:
The persistent API framework provides a query language for retrieval data.They support to write query conditions in an object attribute, instead of directly writing SQL statements.The query language provides a wealth of query functions, including associated queries, sorting, paging, and aggregating operations.
3. Programming example of the persistent API framework
Below is a programming example using Hibernate as a persistent API framework:
3.1. Create a physical class:
public class User {
private Long id;
private String name;
private int age;
// omit the getter and setter method
}
3.2. Configure Hibernate parameter:
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/mydb</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">password</property>
<!-omit other configuration->
</session-factory>
</hibernate-configuration>
3.3. Create data access objects (DAO):
public class UserDAO {
private SessionFactory sessionFactory;
public void setSessionFactory(SessionFactory sessionFactory) {
this.sessionFactory = sessionFactory;
}
public void save(User user) {
Session session = sessionFactory.getCurrentSession();
session.save(user);
}
public User getById(Long id) {
Session session = sessionFactory.getCurrentSession();
return session.get(User.class, id);
}
}
3.4. Use the persistent API framework for data operation:
public class Main {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
UserDAO userDAO = context.getBean(UserDAO.class);
User user = new User();
user.setName("Alice");
user.setAge(25);
userDAO.save(user);
User savedUser = userDAO.getById(user.getId());
System.out.println (SaveDuser.getName ()); // Output: Alice
}
}
In the above example, we use Hibernate as a persistent API framework.A database connection parameters are set in the configuration file, and a User physical class and a UserDao data access object is created.Save user data by calling UserDao's Save method and query user data through ID.
in conclusion:
The persistent API framework in the Java class library provides convenient and efficient data persistence solutions through objective relationship mapping, database connection management, transaction management, cache management and query language and other technical principles.Developers can simplify database operations through the high -level abstraction provided by the framework, and improve the performance and maintenance of the application.
