我想使用@OneToMany关系在数据库中插入数据，但是它不起作用。
我有两个表，其架构如下：
创建表讲师（Id int主键，名称varchar2（50），电子邮件varchar2（15））;
创建表课程（Course_Id int主键，Course_Name Varchar2（20）NOT NULL唯一，Instructor_Id int，外键（Instructor_Id）引用教师（Id））；
当我尝试在db中插入时，它没有给我任何错误，但是在db中却没有反映两个表
课程：
@Entity
@Table(name = "Courses")
public class Courses {
@Id
@Column(name = "Course_Id ")
private int courseId;
@Column(name = "Course_Name")
private String courseName;
@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "Instructor_Id")
private Instructor instructor;
public int getCourseId() {
return courseId;
}
public void setCourseId(int courseId) {
this.courseId = courseId;
}
public String getCourseName() {
return courseName;
}
public void setCourseName(String courseName) {
this.courseName = courseName;
}
public Instructor getInstructor() {
return instructor;
}
public void setInstructor(Instructor instructor) {
this.instructor = instructor;
}
}
讲师：
@Entity
@Table(name = "Instructor")
public class Instructor {
@Id
@Column(name = "Id")
private int id;
@Column(name = "Name")
private String name;
@Column(name = "Email")
private String email;
@OneToMany(mappedBy = "instructor", cascade = CascadeType.ALL)
private List<Courses> courses;
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 String getEmail() {
return email;
}
public List<Courses> getCourses() {
return courses;
}
public void setCourses(List<Courses> courses) {
this.courses = courses;
}
public void setEmail(String string) {
this.email = string;
}
主类：
public class HibernateTest {
public static void main(String[] args) {
try (SessionFactory factory = new Configuration().configure("hibernate.cfg.xml")
.addAnnotatedClass(Courses.class).addAnnotatedClass(Instructor.class).buildSessionFactory();) {
//Test Insert
Instructor i1 = new Instructor();
i1.setEmail("[email protected]");
i1.setId(100);
i1.setName("patcyy");
//List Of Courses
List<Courses> listOfCourses = new ArrayList<>();
Courses c1 = new Courses();
c1.setCourseName("Java");
c1.setCourseId(1);
Courses c2 = new Courses();
c2.setCourseName("C");
c2.setCourseId(2);
listOfCourses.add(c1);
listOfCourses.add(c2);
//adding to instructor
i1.setCourses(listOfCourses);
//insert in DB
inserIntoDb(factory, i1);
} catch (Exception e) {
System.out.println("Exception : " + e);
}
}
/**
*
* @param factory
* @param st
*/
private static void inserIntoDb(SessionFactory factory, Instructor st) {
System.out.println("Inserting into DB");
Session session = factory.getCurrentSession();
session.beginTransaction();
session.save(st);
session.getTransaction().commit();
}
}
日志：
May 13, 2019 8:35:24 AM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {5.4.2.Final}
May 13, 2019 8:35:25 AM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {5.1.0.Final}
May 13, 2019 8:35:25 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using Hibernate built-in connection pool (not for production use!)
May 13, 2019 8:35:25 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001005: using driver [oracle.jdbc.driver.OracleDriver] at URL [jdbc:oracle:thin:@localhost:1521:****]
May 13, 2019 8:35:25 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {user=****, password=****}
May 13, 2019 8:35:25 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
May 13, 2019 8:35:25 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl$PooledConnections <init>
INFO: HHH000115: Hibernate connection pool size: 1 (min=1)
May 13, 2019 8:35:25 AM org.hibernate.dialect.Dialect <init>
INFO: HHH000400: Using dialect: org.hibernate.dialect.Oracle12cDialect
Inserting into DB
Hibernate: select courses_.Course_Id, courses_.Course_Name as Course_Name2_0_, courses_.Instructor_Id as Instructor_Id3_0_ from Courses courses_ where courses_.Course_Id=?
Hibernate: select courses_.Course_Id, courses_.Course_Name as Course_Name2_0_, courses_.Instructor_Id as Instructor_Id3_0_ from Courses courses_ where courses_.Course_Id=?
Hibernate: insert into Instructor (Email, Name, Id) values (?, ?, ?)
更新的代码：
package com.patcyy.hibernate;
import java.util.ArrayList;
import java.util.List;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateTest {
public static void main(String[] args) {
try (SessionFactory factory = new Configuration().configure("hibernate.cfg.xml")
.addAnnotatedClass(Courses.class).addAnnotatedClass(Instructor.class).buildSessionFactory();) {
//Test Insert
Instructor i1 = new Instructor();
i1.setEmail("[email protected]");
i1.setId(100);
i1.setName("patcyy");
//List Of Courses
List<Courses> listOfCourses = new ArrayList<>();
Courses c1 = new Courses();
c1.setCourseName("Java");
c1.setCourseId(1);
c1.setInstructor(i1);
Courses c2 = new Courses();
c2.setCourseName("C");
c2.setCourseId(2);
c2.setInstructor(i1);
listOfCourses.add(c1);
listOfCourses.add(c2);
//adding to instructor
i1.setCourses(listOfCourses);
//insert in DB
inserIntoDb(factory, i1);
} catch (Exception e) {
System.out.println("Exception : " + e);
}
}
/**
*
* @param factory
* @param st
*/
private static void inserIntoDb(SessionFactory factory, Instructor st) {
System.out.println("Inserting into DB");
Session session = factory.getCurrentSession();
session.beginTransaction();
session.save(st);
session.getTransaction().commit();
}
}
在调试时，它会成功。
Debug
配置：
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- JDBC Database connection settings -->
<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="connection.url">jdbc:oracle:thin:@localhost:1521:patcyy</property>
<property name="connection.username">SYSTEM</property>
<property name="connection.password">patcyy</property>
<!-- JDBC connection pool settings ... using built-in test pool -->
<property name="connection.pool_size">1</property>
<!-- Select our SQL dialect -->
<property name="dialect">org.hibernate.dialect.Oracle12cDialect</property>
<!-- Echo the SQL to stdout -->
<property name="show_sql">true</property>
<!-- Set the current session context -->
<property name="current_session_context_class">thread</property>
</session-factory>
</hibernate-configuration>
最佳答案
@Entity
@Table(name = "Instructor")
public class Instructor {
@OneToMany(mappedBy = "instructor", cascade = CascadeType.ALL)
private List<Courses> courses;
}
这里的mappingBy表示
instructor中的Courses用于维护Instructor和Courses关系。 Hibernate将基于此值而不是course中的Instructor来为此关系更新相关外键的值。您正在做的是在
course中设置Instructor的值，而不是在instructor中设置Courses的值，这就是为什么它们的关系永远不会更新的原因。您必须在instructor中设置Courses的值：Courses c1 = new Courses();
c1.setCourseName("Java");
c1.setCourseId(1);
c1.setInstructor(i1);