hibernate--------集合映射

今天改了一整天終于搞出來了，用的打注解的方式，用部門和員工間的關(guān)聯(lián)關(guān)系做例子（打注解實在是比寫xml方便多了....）。
一個部門有多個員工。
代碼如下
1.創(chuàng)建部門和員工的實體類，并打上注解
（1）員工類
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）部門類
package dayentity;

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

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_dept")
public class Dept {

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private  int dno;
private String name;
@OneToMany
@Column(name="id")
private Set<Employee> 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<Employee> getEmployee() {
    return employee;
}
public void setEmployee(Set<Employee> employee) {
    this.employee = employee;
}

}

（3）記得把類文件加載到hibernate.cfg.xml文件中，然后寫測試類
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("錘錘");

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

}

最后應(yīng)該有三張表

....放不了圖..就不看了

補充一點 級聯(lián)操作 cascade 應(yīng)該寫在set配置里

有四種選擇 all 所有操作都進行級聯(lián)操作
save_update 只有在保存和更新時才進行級聯(lián)操作
delete 只有在刪除時進行級聯(lián)操作
none 所有操作都不進行級聯(lián)操作

補充一下 用寫配置文件的方式做一對多映射
（1）寫實體類
部門類
package day31;

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

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;

public class Dept {

private  int dno;
private String name;

private Set<Employee> 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<Employee> getEmployee() {
    return employee;
}
public void setEmployee(Set<Employee> employee) {
    this.employee = employee;
}

}
員工類
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
部門類
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="day31">

<class name="Dept" table="dept">
    <id name="dno" column="dno" type="integer">
        <generator class="native"/>
    </id>
    <property name="name"/>
    <set name="employee" table="employee">
    <key column="dno"></key>
    <one-to-many class="day31.Employee"/>
    </set>
    
</class>

</hibernate-mapping>
員工類

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="day31">

<class name="Employee" table="employee">
    <id name="id" column="id" type="integer">
        <generator class="native"/>
    </id>
    <property name="name"/>
  
</class>

</hibernate-mapping>
（3）
測試類
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();

}

}

最后編輯于 ：
?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請聯(lián)系作者
【社區(qū)內(nèi)容提示】社區(qū)部分內(nèi)容疑似由AI輔助生成，瀏覽時請結(jié)合常識與多方信息審慎甄別。
平臺聲明：文章內(nèi)容（如有圖片或視頻亦包括在內(nèi)）由作者上傳并發(fā)布，文章內(nèi)容僅代表作者本人觀點，簡書系信息發(fā)布平臺，僅提供信息存儲服務(wù)。

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容