Java 类库中 Hibernate Commons Annotations 框架的技术原理详解 (Detailed Explanation of Technical Principles of Hibernate Commons Annotations Framework in Java Class Libraries)

Hibernate Commons Annotions is a sub -framework in the Hibernate framework. It provides support for annotations that enable developers to use the annotation configuration and define persistence physical class.This article will explain the technical principles of the Hibernate Commons Annotations framework and provide related Java code examples. ## 1. What is Hibernate Commons Annotations? Hibernate Commons Annotions is an open source Java annotation framework that provides comments on the basis of the Hibernate framework.With the help of Hibernate Commons Annotations, developers can describe and configure durable physical classes through annotations, without using XML configuration files. ## 2. Hibernate Commons Annotations technical principles Hibernate Commons Annotations defines and configure the physical class to map to the database table through Java annotations.The following is the technical principle of Hibernate Commons Annotations to implement physical class mapping: ### 2.1 physical class annotation Developers can mark this class as the Hibernate entity class by adding `@Entity` annotations on the physical class.For example: @Entity public class User { // The attributes and methods of the physical class } ### 2.2 Primary key annotation By adding the `@ID` annotation, developers can mark the attributes of the physical class as the primary key of the database table.For example: @Entity public class User { @Id private Long id; // Other attributes and methods } ### 2.3 Table name and field annotation Using the `@table` annotation can specify the table name mapped to the database.For example: @Entity @Table(name = "users") public class User { // Attributes and methods } Using the `@column` annotation can specify the name of the attributes of the physical class to the name of the database.For example: @Entity public class User { @Id private Long id; @Column(name = "name") private String userName; // Other attributes and methods } ### 2.4 Relationship annotation Hibernate Commons Annotations also supports the relationship between the physical class. You can use the annotations of ``@onetomany`,@manytoone`, ``@@Manytomany` and other annotations.For example: @Entity public class User { @Id private Long id; @OneToMany(mappedBy = "user") private List<Order> orders; } @Entity public class Order { @Id private Long id; @ManyToOne @JoinColumn(name = "user_id") private User user; // Other attributes and methods } ### 2.5 Other annotations The annotations supported by Hibernate Commons Annotations also include `@Transient` (for marking the attributes that do not require persistence to databases) and `@generatedvalue` (for the primary key value of automatic generating).Developers can choose to use these annotations according to actual needs. ## 3. Example of using Hibernate Commons Annotations The following is a simple example of the persistence of the physical class using the Hibernate Commons Annotations: @Entity @Table(name = "users") public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(name = "name") private String userName; // Other attributes and methods } public class Main { public static void main(String[] args) { // Create Hibernate sessionFactory SessionFactory sessionFactory = new Configuration().addAnnotatedClass(User.class).configure().buildSessionFactory(); // Create hibernate session Session session = sessionFactory.openSession(); // Open transaction Transaction transaction = session.beginTransaction(); // Permanent physical category User user = new User(); user.setUserName("Alice"); session.save(user); // Submit a transaction transaction.commit(); // Turn off session and sessionFactory session.close(); sessionFactory.close(); } } In the above examples, add the category to the `USERS` table to add the`@Entity` and@TABLE` annotations to the physical class `user`.Use the `@id` and@generatedvalue` to define the main key, and the annotation of`@column` defines the mapping relationship between the `username` attribute and the` name` column. In the main program, we create the `sessionFactory` and` session` objects, and then open the transaction and persist the entity class.Finally, submit transactions and close session and sessionFactory. ## Summarize This article details the technical principles of the Hibernate Commons Annotations framework.By using Java annotations, developers can easily configure and define the persistence of physical classes.It is hoped that readers can learn about the basic principles of Hibernate Commons Annotations and apply the framework in actual projects to improve development efficiency.