java - 在 OneToMany 的情况下不会发生数据库插入

Question

我想使用 @OneToMany 关系在数据库中插入数据，但它不起作用。

我有两个表，其架构如下:

创建表讲师(Id int 主键，姓名 varchar2(50),Email varchar2(15))；

创建表类(class)(Course_Id int 主键，Course_Name Varchar2(20) NOT NULL Unique,Instructor_Id int ，外键(Instructor_Id)引用讲师(Id))；

当我尝试插入数据库时​​，它没有给我任何错误，但在数据库中它没有反射(reflect)两个表

类(class):

@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;
    }

}

导师:

@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("test@mail.com");
            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("test@mail.com");
                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();

        }
}

调试成功。

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>

Answer 1

@Entity
@Table(name = "Instructor")
public class Instructor {

    @OneToMany(mappedBy = "instructor", cascade = CascadeType.ALL)
    private List<Courses> courses;
}

这里的ma​​ppedBy表示Courses中的instructor用于维护Instructor和Courses 关系。 Hibernate 将根据该值而不是 Instructor 中的 course 更新此关系的相关外键值。

您正在做的是在 Instructor 中设置 course 的值，而不是在 Courses 中设置 instructor ，这就是为什么他们的关系永远不会更新。您必须在类(class)中设置instructor的值:

Courses c1 = new Courses();
c1.setCourseName("Java");
c1.setCourseId(1);
c1.setInstructor(i1);