The technical principles of the Kodo framework in the Java library
The technical principles of the Kodo framework in the Java library
Kodo is a Java persistence framework to simplify the process of interaction with databases.It is based on the JDO (Java data object) specification and provides a solution for object-relationship mapping (ORM) to enable developers to operate databases in an object-oriented manner.
The technical principles of Kodo mainly include the following aspects:
1. Object-relationship mapping (ORM): Kodo realizes the mapping relationship between the Java class and the database table through ORM.Developers only need to define the Java classes and use annotations or XML configuration to map the attributes to columns in the database table. The Kodo will automatically perform objects to the mapping and persistent operation of the database.
2. EntityManager: Kodo provides entrances that interact with durable entities.The entity manager is responsible for managing functions such as life cycle, transaction operation, and query of the physical object.Developers can perform physical CRUD operations through the entity manager, and Kodo automatically handles associated relationships and class joint operations.
3. Calling mechanism: Kodo improves performance and efficiency by maintaining the cache of the entity object in memory.The cache can reduce the number of interaction with the database, and allows the entity object to share between different transactions, providing better performance and resource utilization.
4. Transparent transaction management: Kodo realizes transaction management through JTA (Java Affairs API) or local affairs managers.Developers can use annotations or XML configurations to declare the boundary of the transaction. Kodo will automatically manage the transaction to ensure the consistency and integrity of the data.
5. Query Language Support: Kodo supports a query language similar to SQL, called Kodo query Language (KQL for short).KQL provides rich query functions, including projection, filtering, sorting and aggregation, etc. Developers can use KQL to write complex query statements and search the required data from the database.
Below is a simple example code that demonstrates how to use Kodo for the persistence of objects:
import javax.persistence.*;
@Entity
public class Person {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String name;
private int age;
// Getter and Setter methods
}
public class Main {
public static void main(String[] args) {
EntityManagerFactory emf = Persistence.createEntityManagerFactory("kodo-pu");
EntityManager em = emf.createEntityManager();
// Start a transaction
em.getTransaction().begin();
// Create a new Person object
Person person = new Person();
person.setName("John Doe");
person.setAge(30);
// Persist the object into the database
em.persist(person);
// Commit the transaction
em.getTransaction().commit();
// Close the EntityManager and EntityManagerFactory
em.close();
emf.close();
}
}
In the above code, we first define a physical category Person, and use notes to illustrate the mapping relationship with the database table.We then created an EntityManager and performed the objective operation of the object.Finally, we submitted changes to the database in the affairs and closed the EntityManager and EntityManagerFactory.
When using the Kodo framework, it is also necessary to configure a persistent unit called "Kodo-PU". The unit will specify the related configuration of the connection information of the database.The configuration file is usually an XML file called "Persistence.xml", which contains configuration information related to the database connection.
To sum up, the Kodo framework simplifies the process of Java developers and database interaction by providing functions such as ORM, entity manager, cache mechanism, transaction management and query language, and improves development efficiency.It can greatly simplify the writing of the database operation code and provide high -performance data access and persistent solutions.
