@OneToMany单向一对多
Hibernate单项一对多详细配置：
数据模型：
一个年级有多个学生，每个学生只属于一个年级。
用hibernate实现一对多关系有xml配置和注解两种方式，下面逐一介绍：
第一种：注解方式
Grade.java
package cn.siggy.pojo;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.MappedSuperclass;
import javax.persistence.OneToMany;
import javax.persistence.Table;
/**
* AbstractGrade entity provides the base persistence definition of the Grade
* entity. @author MyEclipse Persistence Tools
*/
@Entity
@Table(name = "GRADE")
public class Grade implements java.io.Serializable {
// Fields
private Integer id;
private String name;
private Set students = new HashSet(0);
// Constructors
public Grade() {
super();
// TODO Auto-generated constructor stub
}
public Grade(Integer id, String name, Set students) {
super();
this.id = id;
this.name = name;
this.students = students;
}
// Property accessors
@Id
@GeneratedValue
@Column(name = "ID", unique = true, nullable = false, precision = 10, scale = 0)
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
@Column(name = "NAME")
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
@OneToMany(cascade=CascadeType.ALL,fetch=FetchType.LAZY,targetEntity=Student.class)
//@JoinColumn(name="GRADE_ID",nullable=true) //该配置在单独保存Grade是会将student中的外键字段置空，所以采用下面配置
@JoinColumn(name="PLAN_ID",updatable=false)
public Set getStudents() {
return this.students;
}
public void setStudents(Set students) {
this.students = students;
}
} Student.java
package cn.siggy.pojo;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.MappedSuperclass;
import javax.persistence.Table;
/**
* AbstractStudent entity provides the base persistence definition of the
* Student entity. @author MyEclipse Persistence Tools
*/
@Entity
@Table(name = "STUDENT")
public class Student implements java.io.Serializable {
// Fields
private Integer id;
private String name;
private Integer age;
// Constructors
/** default constructor */
public Student() {
}
// Property accessors
@Id
@GeneratedValue
@Column(name = "ID", unique = true, nullable = false, precision = 10, scale = 0)
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
@Column(name = "NAME", length = 510)
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
@Column(name = "AGE", precision = 10, scale = 0)
public Integer getAge() {
return this.age;
}
public void setAge(Integer age) {
this.age = age;
}
}
oracle.jdbc.driver.OracleDriver
jdbc:oracle:thin:@10.18.100.126:1521:gsdb
db_lzsmw
pass_lzsmw
org.hibernate.dialect.Oracle10gDialect
true
true
update
第二种：xml配置方式实现一对多
Grade.java
package cn.siggy.pojo;
import java.util.HashSet;
import java.util.Set;
public class Grade {
private int id;
private String name;
private Set students = new HashSet(0);
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;
}
public Set getStudents() {
return students;
}
public void setStudents(Set students) {
this.students = students;
}
}
Grade.hbm.xml
Student.java
package cn.siggy.pojo;
public class Student {
private int id;
private String name;
private int age;
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;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
Student.hbm.xml
oracle.jdbc.driver.OracleDriver
jdbc:oracle:thin:@10.18.100.126:1521:gsdb
db_lzsmw
pass_lzsmw
org.hibernate.dialect.Oracle10gDialect
true
true
update
工具类：HibernateUtil.java
package cn.siggy.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
private static Configuration cfg=null;
private static SessionFactory factory=null;
private static Session session = null;
static{
cfg = new Configuration().configure();
factory = cfg.buildSessionFactory(new StandardServiceRegistryBuilder()
.applySettings(cfg.getProperties()).build());
}
public static Session getSession(){
if(factory!=null)
return factory.openSession();
factory=cfg.buildSessionFactory(new StandardServiceRegistryBuilder()
.applySettings(cfg.getProperties()).build());
return factory.openSession();
}
public static void closeSession(){
if(session!=null&&session.isOpen())
session.close();
}
}
Junit单元测试类：
package cn.siggy.test;
import java.sql.SQLException;
import java.util.Iterator;
import javax.sql.rowset.serial.SerialException;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.junit.Test;
import cn.siggy.pojo.Grade;
import cn.siggy.pojo.Student;
import cn.siggy.util.HibernateUtil;
public class HibernateTest {
@Test
public void testCreateDB(){
Configuration cfg = new Configuration().configure();
SchemaExport se = new SchemaExport(cfg);
//第一个参数 是否生成ddl脚本 第二个参数 是否执行到数据库中
se.create(true, true);
}
@Test
public void testSave() throws HibernateException, SerialException, SQLException{
Session session = null;
Transaction tx = null;
try{
session = HibernateUtil.getSession();
tx = session.beginTransaction();
Grade grade = new Grade();
grade.setName("基础");
Student stu = new Student();
stu.setName("张三疯");
stu.setAge(22);
Student stu1 = new Student();
stu1.setName("老王");
stu1.setAge(23);
//关联
grade.getStudents().add(stu);
grade.getStudents().add(stu1);
//保存数据的顺序 是根据外键的配置来决定的
//如果外键不能为null,那么先保存一的一端
//如果外键可以为null,则可以随意保存
session.save(grade);
session.save(stu);
session.save(stu1);
tx.commit();
}catch (HibernateException e) {
if(tx!=null)
tx.rollback();
e.printStackTrace();
throw e;
}finally{
HibernateUtil.closeSession();
}
}
@Test
public void testGet(){
Session session = null;
Transaction tx = null;
try{
session = HibernateUtil.getSession();
tx = session.beginTransaction();
//取数据
Grade grade = (Grade)session.get(Grade.class, 1);
System.out.println("gradeName="+grade.getName());
System.out.println("grade所对应的多的一端的数据");
Iterator iter = grade.getStudents().iterator();
for(;iter.hasNext();){
Student temp = iter.next();
System.out.println("name="+temp.getName()+"\tage="+temp.getAge());
}
tx.commit();
}catch (HibernateException e) {
if(tx!=null)
tx.rollback();
e.printStackTrace();
throw e;
}finally{
HibernateUtil.closeSession();
}
}
}
如下表结构代码可以自动生成，所以不用手动创建
Student表结构：
Grade表结构：
