Detailed explanation of UJO ORM framework technical principles in the Java class library
UJO ORM framework technical principle detailed explanation
introduction:
ORM (object relationship mapping) is a technology that converts the data in the relationship database into an object.The UJO ORM framework in the Java class library provides a simple and efficient way to achieve ORM.This article will introduce the technical principles of the UJO ORM framework in detail, including its basic concepts, core components, and use examples.
1. UJO ORM framework overview:
The UJO ORM framework is an open source project developed by the British software developer "Dan GOWER".It aims to simplify the data interaction between Java applications and relational databases.This framework provides many convenient functions, such as automatically generating SQL statements, object relationship mapping, conventional inquiries, and transaction management.
2. Core component of the UJO ORM framework:
The core component of the UJO ORM framework includes:
2.1. MetaModel:
Ujo Orm uses Metamodel to describe the mapping relationship between the Java class and the database table.It allows developers to use annotations or configuration files to define physical classes, attributes, associated relationships and constraints.Through Metamodel, UJO ORM can dynamically generate SQL statements and implement the mapping between objects and databases.
2.2. DataSet:
DataSet is a data operation object model of UJO ORM.It provides many methods to perform query, update, delete and insert operations.Using DataSet, developers can easily interact with the database without manually writing SQL statements.
2.3. Key:
Key is the primary key object in UJO ORM, which indicates the unique identifier of the physical class.Developers can use Key objects to set and obtain the primary key value of the physical class.
3. The working principle of the UJO ORM framework:
The process of using the UJO ORM framework is as follows:
3.1. Define the physical class:
First, developers need to define the physical class.Through annotations or configuration files, the Java class and database tables are mapped, and primary keys, attributes and associations are set.
3.2. Create dataset:
Next, developers need to create DataSet objects.DataSet provides many methods, such as CreateQuery, Insert (insert data), update (update data), and delete (delete data).
3.3. Execute data operation:
Through the DataSET object, developers can perform various data operations, such as querying, updating, inserting, and deleting.
3.4. Search for query results:
Developers can use the GET () method of DataSet to retrieve data from the query results.
4. Example code of the UJO ORM framework:
Below is a simple example code that demonstrates how to use the UJO ORM framework for data operation:
// Import the corresponding library of UJO ORM framework
import org.apache.ujo.core.*;
import org.apache.ujo.core.*;
// Define the physical class
public class UserEntity extends AbstractUjo {
@Key
public static final Key<UserEntity, Integer> ID = newKey();
public static final Key<UserEntity, String> NAME = newKey();
public static final Key<UserEntity, String> EMAIL = newKey();
// Constructor
public UserEntity(int id, String name, String email) {
set(ID, id);
set(NAME, name);
set(EMAIL, email);
}
}
public class Main {
public static void main(String[] args) {
// Create dataset
DataSet ds = new PDataStore(UserEntity.class);
// Insert data
UserEntity user = new UserEntity(1, "John Doe", "johndoe@example.com");
ds.insert(user);
// Query data
Query<UserEntity> query = ds.createQuery(UserEntity.class);
List<UserEntity> result = query.list();
// Print the query results
for (UserEntity entity : result) {
System.out.println(entity.get(UserEntity.NAME));
}
}
}
The above example introduces how to use the UJO ORM framework to define the physical class, create and execute data operations, and search results.
in conclusion:
The UJO ORM framework is a powerful and easy -to -use Java class library to simplify data interaction between Java applications and relational databases.It maps the Java class with the database table through Metamodel and uses the DataSet object to perform various data operations.Whether it is small or large projects, the UJO ORM framework is a practical tool that can improve development efficiency and reduce maintenance costs.
