In -depth understanding of the technical principles of the UJO ORM framework in the Java class library

The UJO ORM framework is a powerful Java class library to simplify the process of data persistence.It provides a simple and efficient way to manage the relationship between Java objects and map these objects into the relational database.This article will explore the technical principles of the UJO ORM framework in the Java class library, and deepen the understanding through the Java code example. The core goal of UJO ORM is to establish a one -to -one or one -to -many mapping relationship between the Java object and the database table, and provide CRUD (creation, reading, update and deleting) operations.The UJO ORM framework realizes the conversion between objects and databases through a set of annotations and API (application interface).Below is an example of Ujo ORM: First of all, we need to define a Java class and use the annotations provided by UJO ORM to mark it as a physical class.The physical class is the mapping of the database table, and each field corresponds to a column of the table. @Entity(tableName = "users") public class User { @Id private int id; @Column(name = "name") private String name; @Column(name = "age") private int age; // Getters and setters } In the above example, the annotation of `@Entity` is used to mark the` user` class as a physical class, and specify the corresponding table name to be `users`.`@Column` Annotation is used to map the fields in the class to the specific columns, and the corresponding column name specifies the` name` attribute.`@ID` Annotation is used to mark the main key field. Once the physical class definition is complete, we can use the API provided by UJO ORM to perform CRUD operations.The following is a simple example: public class Main { public static void main(String[] args) { // Create a UJO object User user = new User(); user.setId(1); user.setName("John"); user.setAge(30); // Database insert operation UjoManager.save(user); // Database query operation User retrievedUser = UjoManager.find(User.class, 1); System.out.println(retrievedUser.getName()); // 输出：John // Database update operation retrievedUser.setName("Tom"); UjoManager.update(retrievedUser); // Database delete operation UjoManager.delete(retrievedUser); } } In the above example, we first created a `user` object and saved it into the database through the method of` ujomanager.save () `.Next, we use `ujomanager.find ()` method to retrieve the preserved user objects from the database and output its name.Then, we modify the name of the object through the method of `ujomanager.Update ()`, and use the method to delete the object from the database. The UJO ORM framework uses some key technical principles in the background to achieve its functions.One of them is the Java reflection mechanism, which allows us to obtain and operate information at runtime.UJO ORM uses reflection to read the annotation information and perform database operations according to the definition of the annotation. Another important technical principle is JDBC (Java database connection), which is a standard interface for communication between Java and databases.UJO ORM uses JDBC to connect to the database and perform the underlying CRUD operation. In summary, the technical principles of the UJO ORM framework in the Java library include the use of the annotation marker physical class, the use of the Java reflection mechanism to obtain the annotation information, and communicate with the database through JDBC.By using the UJO ORM framework, we can easily manage the mapping relationship between the Java object and the database and realize the CRUD operation of the database.