Question

我是jpa / boot的新手。我在Spring启动应用程序中使用JPA / Hibernate创建了Student和StudentCourse之间的一对多关系。

数据库表是student和student_course。

当我运行SchoolApplication.java时，它失败并显示错误，'表或视图不存在'。

这是一个有效的错误，因为我没有创建表student_course_list，只想在student和student_course表中插入数据。

请问您为什么hibernate正在寻找这个附加表以及如何解决此问题？

日志

Hibernate: 
insert 
into
    student_course_list
    (student, course_list) 
values
    (?, ?)

Caused by: org.springframework.dao.InvalidDataAccessResourceUsageException: could not execute statement; SQL [n/a]; nested exception is org.hibernate.exception.SQLGrammarException: could not execute statement
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:242) ~[spring-orm-4.2.6.RELEASE.jar:4.2.6.RELEASE]

SchoolApplication.java

package com.school;

import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.transaction.annotation.Transactional;

import com.school.domain.Student;
import com.school.domain.StudentCourse;
import com.school.service.StudentServiceInterface;

@EntityScan(basePackages={"com.school.domain"})
@SpringBootApplication
public class SchoolApplication implements CommandLineRunner {

    @Autowired
    protected StudentServiceInterface studentService;

    public static void main(String[] args) {
        SpringApplication.run(SchoolApplication.class, args);
    }

    @Override
    @Transactional
    public void run(String... strings) throws Exception {

        StudentCourse sc1 = new StudentCourse();
        sc1.setCourseId(new Long(1));
        sc1.setEndDate(null);

        StudentCourse sc2 = new StudentCourse();
        sc2.setCourseId(new Long(2));
        sc2.setEndDate(null);

        //Course List
        List<StudentCourse> studentCourse = new ArrayList();

        studentCourse.add(sc1);
        studentCourse.add(sc2);

        Student student = new Student();
        student.setFirstName("test first");
        student.setLastName("test last");
        student.setCourseList(studentCourse);

        studentService.saveStudent(student);
}
}

学生

@Entity
@Table(name="student")
public class Student {

    @Id
    @Column(name="student_id")
    @GeneratedValue(strategy=GenerationType.AUTO, generator="student_seq_gen")
    @SequenceGenerator(name="student_seq_gen", sequenceName="SEQ_STUDENT")
    private Long studentId;

    @OneToMany( targetEntity=StudentCourse.class, cascade = {CascadeType.ALL} )
    private List<StudentCourse> courseList;

    @Column(name="first_name")
    private String firstName;

    @Column(name="last_name")
    private String lastName;

    @Column(name="gender")
    private char gender;

    @Column(name="date_of_birth")
    private Date dateOfBirth;

    @Column(name="email")
    private String email;

    @Column(name="city")
    private String city;

    // getter and setters
    .....
    .....

StudentCourse

@Entity
@Table(name="student_course")
public class StudentCourse {

    @Id
    @Column(name="student_course_id")
    @GeneratedValue(strategy=GenerationType.AUTO, generator="student_course_seq_gen")
    @SequenceGenerator(name="student_course_seq_gen", sequenceName="SEQ_STUDENT_COURSE")
    private Long studentCourseId;

    @Column(name="student_id")
    private Long studentId;

    @Column(name="course_id")
    private Long courseId;

    @Column(name="end_date")
    private Date endDate;

    // getter and setters
    .....
    .....

更新：

StudentCourse.java：

@Entity
@Table(name="student_course")
public class StudentCourse {

    @Id
    @Column(name="student_course_id")
    @GeneratedValue(strategy=GenerationType.AUTO, generator="student_course_seq_gen")
    @SequenceGenerator(name="student_course_seq_gen", sequenceName="SEQ_STUDENT_COURSE")
    private Long studentCourseId;

    @JoinColumn(name="student_id", nullable = false, updatable = false, insertable = true)
    @ManyToOne
    private Student student;

    @Column(name="course_id")
    private Long courseId;

    @Column(name="end_date")
    private Date endDate;

Answer 1

您没有告诉您的应用程序扫描实体。在您的主类上添加@EntityScan注释。 e.g。

@SpringBootApplication
@EntityScan(basePackages={"com.example.model", "com.example.student.model"})
public class SchoolApplication implements CommandLineRunner {
    ...
}

BTW，@ComponentScan是多余的，@SpringBootApplication就足够了。如果您要查看SpringBootApplication课程，那么您会看到@ComponentScan。

Answer 2

您没有为您的关系定义JoinColumn（或JoinTable ManyToMany）。 Hibernate正在尝试创建一个表student.courseList关系属性。

按如下方式更改您的学生课程：

// You shouldn't need targetEntity, as your collection has the TargetEntity.
// this parameter is only needed if the Generic type is not present 
// (e.g. private List courseList)
@OneToMany( cascade = {CascadeType.ALL}, mappedBy = "student" )
private List<StudentCourse> courseList;

按如下方式更改您的StudentCourse课程：

// Replace studentId with a Relationship
@JoinColumn(name="student_id")
@ManyToOne
private Student student;

这将告诉Hibernate学生关系 - ＆gt; StudentCourse由Student拥有，并由student_course表中的student_id列映射。

JPA / Hibernate在spring boot application

2 个答案: