Explore the technical principles of the UJO ORM framework in the Java class library
The technical principle of UJO ORM framework in the Java library
UJO ORM (Object/Relational Mapping) is an open source Java framework to simplify the mapping operation between the Java object and the relationship database.Its technical principle is based on the Java's reflection mechanism and annotation function, providing a convenient way to handle the conversion between the object and the database, and realize the relevant database operation.
The main technical principles of the UJO ORM framework are as follows:
1. Note and reflection mechanisms: UJO ORM uses Java's reflection mechanism and annotations to achieve the mapping and database operation of the object.By adding annotations to the Java class, developers can specify the mapping relationship between classes, the mapping relationship between fields and columns, and various attributes that define database operations.At the same time, UJO ORM can dynamically read and modify the attributes of the Java object during runtime, and map it to the corresponding fields in the database.
2. Database connection management: UJO ORM provides the management of database connection pools, reducing the overhead of the database connection.Developers can specify the relevant information of the database in the configuration file, including database types, drivers, connecting URLs and account passwords.UJO ORM will automatically establish a database connection based on these configuration information and provide a simple API to operate the database.
3. Object-Relationship mapping: UJO ORM uses the object-relationship mapping method to process the mapping relationship between the Java object and the database table.Developers can use annotations to specify the mapping relationship between objects and tables, and set the corresponding relationship between fields and columns.UJO ORM will automatically generate SQL statements based on the annotation configuration to realize data conversion between objects and databases.
4. Entity operation: UJO ORM provides a set of APIs to operate the entity increase, delete, change, and check.By using the unified interface provided by UJO ORM, developers can easily perform database operation without writing complex SQL statements.For example, you can save the entity into the database by calling the Save () method, or load the data in the database by calling the load () method to the corresponding entity object.
Below is a sample code using the UJO ORM framework:
import org.ujorm.orm.*;
public class User extends OrmTable<User> {
@Column(pk = true)
private Integer id;
@Column(length = 50, uniqueIndex = "idx_username")
private String username;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public static void main(String[] args) {
OrmHandler handler = new OrmHandler();
ORMDECORATOR <account> orm = handler.orm (user.class); // Get the ONER class ORM operating object
User user = new User();
user.setId(1);
user.setUsername("Alice");
Orem.insert (user); // Insert user entities to database
User loadedUser = ORM.SELECTBYID (1); // Load the user entity from the database through the ID
System.out.println (loadeduser.getusername ()); // Output: "alice"
}
}
In the above sample code, we created a User class and used the annotation of the UJO ORM framework to specify the mapping relationship with the database table.In the main method, we used Ujo ORM's API for insertion and query operations.
In short, the technical principle of the UJO ORM framework in the Java class library is based on the reflection mechanism and annotation function of Java. Through object-relationship mapping and database connection management, it provides a convenient way to handle the mapping relationship and database between the object and the database and the database.operate.By using UJO ORM, developers can develop database development more efficiently.
