Hibernate unidirectional Association N-1

Hibernate unidirectional Association N-1
N-1 Association for connectable

Multiple employees are associated with one Department.

Employee entity (N-side ):

Package com. ydoing. hibernate2; import javax. persistence. cascadeType; import javax. persistence. column; import javax. persistence. entity; import javax. persistence. fetchType; import javax. persistence. generatedValue; import javax. persistence. generationType; import javax. persistence. id; import javax. persistence. joinColumn; import javax. persistence. joinTable; import javax. persistence. manyToOne; import javax. persistence. table; @ Entity @ Table (name = employee_inf) public class Employee {@ Id @ Column (name = employee_id) @ GeneratedValue (strategy = GenerationType. IDENTITY) private Integer id; // One-Way Association of N-1 @ ManyToOne (targetEntity = Department. class, cascade = CascadeType. ALL, fetch = FetchType. LAZY) // @ JoinColumn (name = department_id, nullable = false) @ JoinTable (name = employee_department, // join table name joinColumns = @ JoinColumn (name = employee_id, referencedColumnName = employee_id, unique = true), inverseJoinColumns = @ JoinColumn (name = department_id, referencedColumnName = department_id) private Department ;.... omitting the get and set methods...

Department entity (1 side ):

Package com. ydoing. hibernate2; import javax. persistence. column; import javax. persistence. entity; import javax. persistence. generatedValue; import javax. persistence. generationType; import javax. persistence. id; import javax. persistence. table; @ Entity @ Table (name = department_inf) public class Department {@ Id @ Column (name = department_id) @ GeneratedValue (strategy = GenerationType. IDENTITY) private Integer id; private String name ;.... omitting the get and set methods...

Test:

package com.ydoing.hibernate2;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.cfg.Configuration;import org.hibernate.service.ServiceRegistry;import org.junit.BeforeClass;import org.junit.Test;public class Main {    private static Session session;    @BeforeClass    public static void init() {        Configuration conf = new Configuration();        conf.configure();        ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(conf.getProperties())                .build();        SessionFactory factory = conf.buildSessionFactory(serviceRegistry);        session = factory.openSession();    }    @Test    public void test() {        Employee emp = new Employee();        emp.setName(Jack);        emp.setAge(20);        emp.setDepartment(new Department(dev));        Transaction tx = session.getTransaction();        tx.begin();        session.save(emp);        tx.commit();        session.close();    }}

Console output:

Hibernate:     insert     into        department_inf        (name)     values        (?)Hibernate:     insert     into        employee_inf        (age, department_id, name)     values        (?, ?, ?)

From the above output, it cannot be seen that Hibernate inserts the ss_inf of the main table first, and then persistently inserts the INF ss_inf from the table. No connected table is generated. However, the foreign key column "department_id" is exclusive to "employee_inf.

Data Table:

N-1 associations with connection tables

Use the preceding columns to modify the Employee class:

Package com. ydoing. hibernate2; import javax. persistence. cascadeType; import javax. persistence. column; import javax. persistence. entity; import javax. persistence. generatedValue; import javax. persistence. generationType; import javax. persistence. id; import javax. persistence. joinColumn; import javax. persistence. joinTable; import javax. persistence. manyToOne; import javax. persistence. table; @ Entity @ Table (name = employee_inf) public class Employee {@ Id @ Column (name = person_id) @ GeneratedValue (strategy = GenerationType. IDENTITY) private Integer id; // N-1 one-way connected table Association @ ManyToOne (targetEntity = Department. class, cascade = CascadeType. ALL) // @ JoinColumn (name = department_id, nullable = false) @ JoinTable (name = employee_department, // join table name joinColumns = @ JoinColumn (name = person_id, referencedColumnName = person_id, unique = true), inverseJoinColumns = @ JoinColumn (name = department_id, referencedColumnName = department_id) private Department ;.... omitting the get and set methods...

Console output:

Hibernate:     insert     into        department_inf        (name)     values        (?)Hibernate:     insert     into        employee_inf        (age, name)     values        (?, ?)Hibernate:     insert     into        employee_department        (department_id, person_id)     values        (?, ?)

From the output, we can see that Hiberate has created the employee_department table and joined the two tables, employee_inf and department_inf, without adding foreign key columns.

Data Table: