In -depth understanding of the core principle and architecture design of the "Persistence API" framework
In -depth understanding of the core principle and architecture design of the "Persistence API" framework
introduction:
In today's software development, data persistence is an indispensable part.Data durability involves storing data in the application into the persistence storage system so that the data status can be restored after the program is restarted.In order to simplify the development of developers in data persistence, the "Persistence API" framework came into being.This article will explore the core principles and architecture design of the "Persistence API" framework, and give some related Java code examples.
1. What is the "Persistence API" framework?
"Persistence API" framework is a tool for managing interaction between applications and data storage.It provides a set of API that allows developers to process data in an object -oriented manner without paying attention to the details of data storage.The "Persistence API" framework usually uses ORM (object relationship mapping) technology to convert data storage and object models, so that developers can directly operate the object without writing the lengthy SQL statement.
2. The core principle of "Persistence API"
1. Data Object Mapping:
The "Persistence API" framework realizes the conversion between the object and the database by mapping the data object to the surface structure of the database.Developers can define the mapping relationship between data objects and database tables by commentary or configuration files. The framework will automatically store and retrieve data based on these mapping relationships.
For example, consider a simple Java class Person, which means a person's basic information:
@Entity
@Table(name = "person")
public class Person {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
private int age;
// omitted getters and setters
}
In the above example,@Entity annotation indicates that the Person class is a physical class,@Table annotation specifies the corresponding table name in the database.Essence
2. Persistence Context:
The "Persistence API" framework introduces the concept of persistent context to manage the state of data objects.The persistence context is a mechanism similar to cache. It tracks and automatically manages the state changes of the object, including the creation, update and deletion of the object.
Developers can perform data operations by persistent APIs, such as saving, updating or deleting objects.When performing these operations, the framework will automatically synchronize the state of the object to the database.
The following is an example of data operation using the "Persistence API" framework:
EntityManagerFactory emf = Persistence.createEntityManagerFactory("myapp");
EntityManager em = emf.createEntityManager();
EntityTransaction tx = em.getTransaction();
try {
tx.begin();
// Create a new Person object
Person person = new Person();
person.setName("Tom");
person.setAge(30);
// Save the object in the database
em.persist(person);
tx.commit();
} catch (Exception e) {
if (tx != null) {
tx.rollback();
}
} finally {
em.close();
emf.close();
}
In the above examples, a EntityManager object was created through EntityManagerFactory.Then, start a transaction and create a new Person object to save it into the database.Finally, if the operation is successful, the transaction is submitted, otherwise the rollback operation is performed.
Third, the architecture design of "Persistence API"
The "Persistence API" framework generally adopts hierarchical architecture design, including the following key components:
1. ORM Engine:
The ORM engine is the core component of the "Persistence API" framework.It is responsible for mapping the data object to the database table, as well as the conversion operation between the data object and the database.The ORM engine usually relies on the following two sub -components to complete the work:
-Metadata Tools: Metropolitan data tools are used to collect and process object mapping information defined by developers.This information includes the field of the object, the main key, the relationship between the association, etc.The ORM engine uses metadata tools to generate the structure of the database table, and the conversion between objects and databases is performed according to metadata in the data operation.
-SQL generator: SQL generator is responsible for generating the corresponding SQL statement according to the operation of the object.The ORM engine executes data into, updated, deletes, and query operations through SQL generators.According to the specific implementation, the SQL generator can generate standard SQL statements, and can also generate SQL statements of specific databases.
2. Transaction Manager:
The transaction manager is used to manage the transaction operation of the database.It is responsible for turning, submitting or rolling affairs, and ensuring the consistency and integrity of the database during the execution of the transaction.
3. Connection Pool:
The connection pool is a component for managing the database connection.It improves the performance and efficiency of data access by maintaining a set of reusable database connections.The distribution and recycling of the connection database connection database connection to the database connection to frequently create and close the database connection.
Fourth, summary
The "Persistence API" framework simplifies the development of developers in data persistence by providing a set of APIs and core components.Its core principles include the concept of data object mapping and persistent context.The architecture design of the framework adopts a hierarchical structure and rely on components such as the ORM engine, transaction manager and connection pool to complete the data operation.
By in -depth understanding of the "Persistence API" framework, developers can better apply this framework to improve the efficiency and quality of software development.
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