hibernate--------集合映射

今天改了一整天终于搞出来了，用的打注解的方式，用部门和员工间的关联关系做例子（打注解实在是比写xml方便多了....）。
一个部门有多个员工。
代码如下
1.创建部门和员工的实体类，并打上注解
（1）员工类
package dayentity;

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.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name="tb_emp")
public class Employee {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
@Column(name="name")
private String name;

public int getId() {
    return id;
}
public void setId(int id) {
    this.id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
}

（2）部门类
package dayentity;

import java.util.HashSet;
import java.util.Set;

@Entity
@Table(name="tb_dept")
public class Dept {

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private  int dno;
private String name;
@OneToMany
@Column(name="id")
private Set employee=new HashSet<>();
public int getDno() {
    return dno;
}
public void setDno(int dno) {
    this.dno = dno;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}

public Set getEmployee() {
    return employee;
}
public void setEmployee(Set employee) {
    this.employee = employee;
}

}

（3）记得把类文件加载到hibernate.cfg.xml文件中，然后写测试类
package dayentity;
import java.util.Set;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class test0001 {
public static void main(String[] args) {

    Configuration cfg=new Configuration().configure();
    SessionFactory sessionFactory=cfg.buildSessionFactory();
    Session session=sessionFactory.openSession();
    Transaction ts=session.beginTransaction();
    
    Dept dept=new Dept();
    dept.setDno(111);
    dept.setName("锤锤");

Employee emp=new Employee();
emp.setId(11);
emp.setName("lsj");
dept.getEmployee().add(emp);
session.save(dept);
session.save(emp);
ts.commit();
session.close();
}

}

最后应该有三张表

....放不了图..就不看了

补充一点级联操作 cascade 应该写在set配置里

有四种选择 all 所有操作都进行级联操作
save_update 只有在保存和更新时才进行级联操作
delete 只有在删除时进行级联操作
none 所有操作都不进行级联操作

补充一下用写配置文件的方式做一对多映射
（1）写实体类
部门类
package day31;

import java.util.HashSet;
import java.util.Set;

public class Dept {

private  int dno;
private String name;

private Set employee=new HashSet<>();

public int getDno() {
    return dno;
}
public void setDno(int dno) {
    this.dno = dno;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}

public Set getEmployee() {
    return employee;
}
public void setEmployee(Set employee) {
    this.employee = employee;
}

}
员工类
package day31;

public class Employee {

private int id;

private String name;


public int getId() {
    return id;
}
public void setId(int id) {
    this.id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}

}
（2）配置文件
部门类

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

员工类

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

（3）
测试类
package day31;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class test0001 {
public static void main(String[] args) {

    Configuration cfg=new Configuration().configure();
    SessionFactory sessionFactory=cfg.buildSessionFactory();
    Session session=sessionFactory.openSession();
    Transaction ts=session.beginTransaction();
    
    Dept dept=new Dept();
    dept.setDno(112);
    dept.setName("song");
    
    
Employee emp=new Employee();

emp.setId(12);
emp.setName("dudu");
dept.getEmployee().add(emp);
session.save(dept);
session.save(emp);
ts.commit();
session.close();

}

}

hibernate--------集合映射

你可能感兴趣的:(hibernate--------集合映射)