The technical principles of the UJO ORM framework in the Java library (Technical Principles Analysis of Ujo Orm Framework in Java Class Libraries))
The UJO ORM framework is an object relationship mapping framework widely used in the Java library.It has some important technical principles that make it very efficient and flexible when dealing with database operations.This article will analyze the technical principles of the UJO ORM framework and provide the corresponding Java code example.
1. EO (Entity Object) model: The UJO ORM framework adopts an EO model, which maximize the database table as a Java class and map each line of data in the table to an instance object in this class.By using the EO model, the database can be easily operated.The following is a simple example code:
public class Employee extends Ujo {
public static final Key<Employee, Long> ID = newKey($ID);
public static final Key<Employee, String> NAME = newKey($NAME);
public static final ListKey<Employee, Project> PROJECTS = newListKey($PROJECTS);
public Long getId() {
return get(ID);
}
public void setId(Long id) {
set(ID, id);
}
public String getName() {
return get(NAME);
}
public void setName(String name) {
set(NAME, name);
}
public List<Project> getProjects() {
return getList(PROJECTS);
}
public void setProjects(List<Project> projects) {
setList(PROJECTS, projects);
}
}
The above code defines a physical class called Employee, which has attributes such as ID, name, and projects.In the UJO ORM framework, use the key class definition attributes, and use the get () and set () methods to operate.
2. Database operation API: The UJO ORM framework provides a powerful API for performing various database operations.For example, you can use the save () method to save an object into the database, delete an object with the delete () method, and use the Find () method to query the object that meets specific conditions.The following is an example code that saves the Employee object:
Employee employee = new Employee();
employee.setId(1L);
employee.setName("John Doe");
Session session = new Session();
session.save(employee);
The above code creates a new Employee object and saves it into the database.
3. Powerful query function: The UJO ORM framework provides a rich query function, which can easily perform various complex query.For example, you can use the CRITERION class definition query conditions, use the order of order to define the sorting rules, and use the Project class definition projection query.The following is an example code that query the Employee object:
Criterion criterion = Criterion.where(Employee.NAME, Operator.LIKE, "John%");
List<Employee> employees = session.createQuery(Employee.class)
.add(criterion)
.list();
The above code creates a query that will return all Employee objects that start with "John".
4. Relations mapping: The UJO ORM framework supports multiple relationship mapping, including one -to -one, one -to -many, more to one and more pairs.By defining appropriate attributes and relationship mapping, complex database relationships can be easily handled.The following is a sample code of multi -relationship mapping:
public class Project extends Ujo {
public static final Key<Project, Long> ID = newKey($ID);
public static final Key<Project, String> NAME = newKey($NAME);
public static final Key<Project, Employee> MANAGER = newKey($MANAGER);
public Long getId() {
return get(ID);
}
public void setId(Long id) {
set(ID, id);
}
public String getName() {
return get(NAME);
}
public void setName(String name) {
set(NAME, name);
}
public Employee getManager() {
return get(MANAGER);
}
public void setManager(Employee manager) {
set(MANAGER, manager);
}
}
The above code defines a physical class called Project, which contains a manager attribute.Through this relationship mapping, the manager of a project can be easily found.
In summary, the technical principles of the UJO ORM framework in the Java class library make it a powerful, flexible and easy -to -use object relationship mapping framework.By using the EO model, database operation API, powerful query function and flexible relationship mapping, developers can efficiently perform database operations.
