JPA 参照完整性约束违规 oneToMany 和批量操作查询

My domain model diagram looks like this:

正如您所看到的，我在学生和出勤之间以及出勤和研讨会之间有一个一对多的关系。

下面是学生类和出勤类，以及我的帮助类（初始化程序）。

package com.seminars.domain;

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

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

import org.hibernate.annotations.GenericGenerator;

import com.seminars.util.SimpleCalendar;


@Entity
@Table(name="Student")
public class Student {
    /*start all class fields*/
    @Id
    //@GenericGenerator(name="kaugen" , strategy="increment")
    //@GeneratedValue(generator="kaugen")
    @Column(name="studentId")
    //@GeneratedValue(strategy=GenerationType.AUTO)
    private int studentId;  

    @Column(name="firstname", length=50, nullable = false)
    private String firstname;
    @Column(name="lastname", length=50, nullable = false)
    private String lastname;
    @Column(name="email", length=50, nullable = false)
    private String email;
    @Column(name="username", length=50, nullable = false)
    private String username;
    @Column(name="password", length=50, nullable = false)
    private String password;
    @Column(name="idCard", length=50, nullable = false)
    private String idCard;
    /* end fields*/

    @OneToMany(mappedBy = "student",cascade=CascadeType.ALL) 
    private Set<Attendance> attendance = new HashSet<Attendance>() ; 



    /**
     * default constructor 
     */
    public Student(){

    }

    /**
     * Secondary Constructor to automatically create a Student 
     * @param firstname
     * @param lastname
     * @param email
     * @param username
     * @param password
     * @param idcard
     */
    public Student(String firstname,String lastname,String email, String username,String password, String idcard){
        this.setFirstname(firstname);
        this.setLastname(lastname);
        this.setEmail(email);
        this.setIdCard(idcard);
        this.setPassword(password);
        this.setUsername(username);

    }

    public int getStudentId() {
        return studentId;
    }

    public void setStudentId(int studentId) {
        this.studentId = studentId;
    }

    public String getFirstname() {
        return firstname;
    }

    public void setFirstname(String firstname) {
        this.firstname = firstname;
    }

    public String getLastname() {
        return lastname;
    }

    public void setLastname(String lastname) {
        this.lastname = lastname;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getIdCard() {
        return idCard;
    }

    public void setIdCard(String idCard) {
        this.idCard = idCard;
    }

    /*Methods for connecting Student<------->Attendance*/

    /**
     * @return a new hashset contain 
     * <p>all attendances of the student
     */
    public HashSet<Attendance> getAttendance(){
        return  new HashSet<Attendance>(attendance);        
    }

    /**
     * @param attendance
     * @param seminar
     */
    public void addAttendance(Attendance attendance, Seminar seminar){
        if(attendance!=null & seminar!=null){
            attendance.setStudent(this);
            attendance.setSeminar(seminar);     
            attendance.setRegisterDate((new SimpleCalendar(Calendar.getInstance()))); /* xreiazomaste na orizete I timi apo to sistima automata*/
        }

    }

    /**
     * @param attendance to remove from HashSet
     */
    public void removeAttendance(Attendance attendance){
        attendance.setStudent(null);
    }

    /**
     * @return Attendance HashSet
     */
    public Set<Attendance> findAttendance(){
        return attendance; 
    }

    /* (non-Javadoc)
     * @see java.lang.Object#equals(java.lang.Object)
     */
    public boolean equals(Object other) {
        if ( other == null) {
            return false;
        }
        if (this == other) {
            return true;
        }
        if (! (other instanceof Student)) {
            return false;
        }

        Student theStudent = (Student) other;
        //Integer a=getStudentId();
        //Integer b=theStudent.getStudentId();
        if(!(getIdCard()==null) ? theStudent.getIdCard()==null : getIdCard().equals(theStudent.getIdCard())){
            return false;        
        }
        return true;  
    }

    /* (non-Javadoc)
     * @see java.lang.Object#hashCode()
     */
    public int hashCode() {
        return idCard == null ? 0 : idCard.hashCode();
    }





}

出勤班

/**
 * 
 */
package com.seminars.domain;

import java.util.Calendar;
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.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

import org.junit.Assert;
import org.junit.Test;

import com.seminars.util.SimpleCalendar;


/**
 * @author Ilias
 *
 */
@Entity
@Table(name = "Attendance")
public class Attendance {

    public Attendance() {
        this.registerDate=new SimpleCalendar(Calendar.getInstance());
    }

    @Id
    @Column(name="attendanceId")
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int attendanceId;   

    @Column(name = "registerDate", length = 200, nullable = false)
    //@Temporal(TemporalType.DATE)
    @org.hibernate.annotations.Type(
            type="com.seminars.persistence.SimpleCalendarCustomType")
    private SimpleCalendar registerDate;

    @Column(name = "success")
    private boolean success;

    @ManyToOne
    @JoinColumn(name="studentId", nullable = false)
    private Student student;

    @OneToMany(mappedBy = "attendance",cascade=CascadeType.ALL)  
    private Set<Absence> absence = new HashSet<Absence>() ; 

    @ManyToOne
    @JoinColumn(name="seminarId", nullable = false)
    private Seminar seminar;

    @OneToMany(mappedBy = "attendance",cascade=CascadeType.ALL)  
    private Set<Payment> payment = new HashSet<Payment>() ;/*<<<*/

    public SimpleCalendar getRegisterDate() {
        return registerDate;
    }

    public void setRegisterDate(SimpleCalendar registerDate) {
        this.registerDate = registerDate;
    }

    public boolean isSuccess() {
        return success;
    }

    public void setSuccess(boolean success) {
        this.success = success;
    }

    /**
     * @return the student
     */
    public Student getStudent() {
        return student;
    }

    /**
     * @param student the student to set
     */
    public void setStudent(Student student) {
        //this.student = student.findAttendance().add(this);
        if (this.student != null) {
            this.student.findAttendance().remove(this);
        }
        this.student = student;
        if (this.student != null) {
            this.student.findAttendance().add(this);
        }
    }

    /**
     * @return the seminar
     */
    public Seminar getSeminar() {
        return seminar;
    }

    /**
     * @param seminar the seminar to set
     */
    public void setSeminar(Seminar seminar) {
        //this.student = student.findAttendance().add(this);
                if (this.seminar != null) {
                    this.seminar.findAttendance().remove(this);
                }
                this.seminar = seminar;
                if (this.seminar != null) {
                    this.seminar.findAttendance().add(this);
                }
    }

    public HashSet<Absence> getAbsence(){
        return  new HashSet<Absence>(absence);
    }

    public void addAbsence(Absence absence, SimpleCalendar date){
        if(absence!=null && date!=null){
            absence.setAttendance(this);
            /*stelnoume tin imerominia pou kataxorei I gramamteia oti elipe o foititis*/
            absence.setDate(date);
        }       

    }

    /**
     * @return Absence HashSet
     */
    public Set<Absence> findAbsence(){
        return absence; 
    }

    /**
     * @return HashSet<Payment>
     */
    public HashSet<Payment> getPayment(){
        return  new HashSet<Payment>(payment);
    }

    public void addPayment(Payment payment, SimpleCalendar date){
        if(payment!=null && date!=null){
            payment.setAttendance(this);
            /*stelnoume tin imerominia pou kataxorei I gramamteia oti elipe o foititis*/
            //absence.setDate(date);
        }           
    }
    /**
     * @return Payment HashSet
     */
    public Set<Payment> findPayment(){
        return payment; 
    }

    /* (non-Javadoc)
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object other) {
        if ( other == null) {
            return false;
        }
        if (this == other) {
            return true;
        }
        if (! (other instanceof Attendance)) {
            return false;
        }

        Attendance theAttendance = (Attendance) other;
        //Integer a=getStudentId();
        //Integer b=theStudent.getStudentId();
        if(!(getStudent()==null) ? theAttendance.getStudent()==null : getStudent().equals(theAttendance.getStudent())){
            return false;        
        }
        if(!(getSeminar()==null) ? theAttendance.getSeminar()==null : getSeminar().equals(theAttendance.getSeminar())){
            return false;        
        }
        return true;  
    }

    /* (non-Javadoc)
     * @see java.lang.Object#hashCode()
     */
    public int hashCode() {
        if(student==null && seminar==null){
            return 0;
        }
        else {
            int result=0;
            if(student!=null)
                result+= 13*getStudent().hashCode()/*+getSeminar().hashCode()*/;            
            if(seminar!=null)
                result+= 13*getSeminar().hashCode();            
            return result;
        }
        /*int result = 0;
        result = getStudent() == null ? result : 13 * result + getStudent().hashCode(); 
        result = getSeminar() == null ? result : 13 * result + getSeminar().hashCode();
        return result;  */

    }


}

初始化类

    package com.seminars.persistence;

import java.util.Calendar;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
import javax.persistence.Query;

import com.seminars.domain.Attendance;
import com.seminars.domain.Seminar;
import com.seminars.domain.Student;
import com.seminars.util.SimpleCalendar;




public class Initializer  {
    /* EntityManager em = DatabaseFactory.createEntityManager();
     EntityTransaction tx = em.getTransaction();*/


    //delete all data from database
    public void  eraseData() {
        EntityManager em = DatabaseFactory.getCurrentEntityManager();
        EntityTransaction tx = em.getTransaction();
        tx.begin();

        Query query = em.createNativeQuery("delete from \"Student\"");
        query.executeUpdate();
        query = em.createNativeQuery("delete from \"Absence\"");
        query.executeUpdate();
        query = em.createNativeQuery("delete from \"Attendance\"");
        query.executeUpdate();
        query = em.createNativeQuery("delete from \"Payment\"");
        query.executeUpdate();
        query = em.createNativeQuery("delete from \"Seminar\"");
        query.executeUpdate();
        query = em.createNativeQuery("delete from \"Program\"");
        query.executeUpdate();
        tx.commit();
        em.close();
    }
    public void prepareData() {

        // πριν εισάγουμε τα δεδομένα διαγράφουμε ότι υπάρχει
        eraseData();
        EntityManager em = DatabaseFactory.createEntityManager();
        EntityTransaction tx = em.getTransaction();
        tx.begin();
        Student s1=new Student("george","antoniou","[email protected] /cdn-cgi/l/email-protection","antoniou","password","998456");
        s1.setStudentId(1);
        Student s2=new Student("ilias","butsikakis","[email protected] /cdn-cgi/l/email-protection","ilias","butsi","98756423");
        s2.setStudentId(2);
        Seminar sem1=new Seminar(1, "Java", 5,500, 2, new SimpleCalendar(2013,1,5), new SimpleCalendar(2013,2,5),"100");
        sem1.setSeminarId(1);
        Attendance att=new Attendance();
        att.setRegisterDate(new SimpleCalendar(Calendar.getInstance()));
        //s1.addAttendance(att, sem1);
        //s1=em.merge(s1);
        //s2=em.merge(s2);
        //sem1=em.merge(sem1);
        //em.persist(att);
        em.persist(s1);
        em.persist(s2);
        em.persist(sem1);
        s1.addAttendance(att, sem1);
        em.persist(att);
        s1=em.merge(s1);
        em.persist(s1);
        tx.commit();
        em.close();
    }    

    /*public void prepareData1() {
        // πριν εισάγουμε τα δεδομένα διαγράφουμε ότι υπάρχει  
        eraseData();   
        Student s1=new Student("george","antoniou","[email protected] /cdn-cgi/l/email-protection","antoniou","password","998456");
        s1.setStudentId(1);
        Student s2=new Student("ilias","butsikakis","[email protected] /cdn-cgi/l/email-protection","ilias","butsi","98756423");
        s2.setStudentId(2);
        Seminar sem1=new Seminar(1, "Java", 5,500, 2, new SimpleCalendar(2013,1,5), new SimpleCalendar(2013,2,5),"100");

        //EntityManager em = DatabaseFactory.createEntityManager();
        EntityManager em = DatabaseFactory.createEntityManager();
        EntityTransaction tx = em.getTransaction();                       
        tx.begin();
        em.persist(s1);
        em.persist(s2);
        tx.commit();
        em.close();
        /*NOTE ALWAYS REMEMBER: 
         * 1)Open entity Manager,
         * 2)Open Transaction
         * 3)Create Items
         * else You will need to use merge or you will get a detached exception!!!
         *  */
        //s1=em.merge(s1);
       /* Student s1=new Student("george","antoniou","[email protected] /cdn-cgi/l/email-protection","antoniou","password","998456");
        s1.setStudentId(1);
        Student s2=new Student("ilias","butsikakis","[email protected] /cdn-cgi/l/email-protection","ilias","butsi","98756423");
        s2.setStudentId(2);
        Seminar sem1=new Seminar(1, "Java", 5,500, 2, new SimpleCalendar(2013,1,5), new SimpleCalendar(2013,2,5),"100");
        s1=em.merge(s1);
        s2=em.merge(s2);
        sem1=em.merge(sem1);
        em.persist(s1);
        em.persist(s2);
        em.persist(sem1);
        tx.commit();
        em.close();*/

        /*EntityManagerFactory emf = Persistence.createEntityManagerFactory("library");
        EntityManager em = emf.createEntityManager();*/

    //}    

}

该项目主要通过 JUnit 测试进行检查，因此在 Initializer 类中，我们有一个PrepareData 方法，它创建一些在每次检查中使用的示例数据，以及一个删除方法，以确保每次检查都使用相同的数据完成。

在尝试检查学生和出勤之间的连接之前，一切似乎都正常。我在初始化程序中创建了一个新的出勤对象，以测试学生是否可以“正常”参加研讨会，并且我收到了很多异常消息。

我最注意到的一个（正如它在控制台中所示）是

分段阅读_第 3781 章 违反参照完整性约束：“FKE7E9BF09F9FEB38B： 公开。“出勤”外键（学生）参考资料 PUBLIC.""Student""(""studentId"")"; SQL语句：删除 “学生”[23003-135]

我检查以确保注释和级联位于正确的位置，但没有结果......

我还尝试更改项目在初始值设定项类中保存的顺序，但随后出现其他错误

**javax.persistence.PersistenceException: org.hibernate.PropertyValueException: not-null property references a null or transient value: com.seminars.domain.Attendance.seminar**
    at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1235)
    at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1168)
    at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1174)
    at org.hibernate.ejb.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:674)
    at com.seminars.persistence.Initializer.prepareData(Initializer.java:73)
    at com.seminars.services.ManageStudentServiceTest.setup(ManageStudentServiceTest.java:60)
    at com.seminars.services.ManageStudentServiceTest.testManageStudentService(ManageStudentServiceTest.java:97)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:44)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:180)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:41)
    at org.junit.runners.ParentRunner$1.evaluate(ParentRunner.java:173)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:220)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: org.hibernate.PropertyValueException: not-null property references a null or transient value: com.seminars.domain.Attendance.seminar
    at org.hibernate.engine.Nullability.checkNullability(Nullability.java:101)
    at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:313)
    at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
    at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)
    at org.hibernate.ejb.event.EJB3PersistEventListener.saveWithGeneratedId(EJB3PersistEventListener.java:69)
    at org.hibernate.event.def.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:179)
    at org.hibernate.event.def.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135)
    at org.hibernate.event.def.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:61)
    at org.hibernate.impl.SessionImpl.firePersist(SessionImpl.java:800)
    at org.hibernate.impl.SessionImpl.persist(SessionImpl.java:774)
    at org.hibernate.impl.SessionImpl.persist(SessionImpl.java:778)
    at org.hibernate.ejb.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:668)
    ... 27 more

以下是在更改初始值设定项类中的项目顺序之前出现的异常列表：

> javax.persistence.PersistenceException:
> org.hibernate.exception.ConstraintViolationException: could not
> execute native bulk manipulation query    at
> org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1235)
>   at
> org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1168)
>   at
> org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:1245)
>   at
> org.hibernate.ejb.AbstractQueryImpl.executeUpdate(AbstractQueryImpl.java:108)
>   at
> com.seminars.persistence.Initializer.eraseData(Initializer.java:37)
>   at
> com.seminars.services.ManageStudentServiceTest.empty(ManageStudentServiceTest.java:64)
>   at
> com.seminars.services.ManageStudentServiceTest.testManageStudentService(ManageStudentServiceTest.java:99)
>   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)  at
> sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)   at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)   at
> java.lang.reflect.Method.invoke(Unknown Source)   at
> org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
>   at
> org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
>   at
> org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
>   at
> org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
>   at
> org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
>   at
> org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
>   at
> org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
>   at
> org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:44)
>   at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:180)
>   at org.junit.runners.ParentRunner.access$000(ParentRunner.java:41)
>   at org.junit.runners.ParentRunner$1.evaluate(ParentRunner.java:173)
>   at
> org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
>   at
> org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
>   at org.junit.runners.ParentRunner.run(ParentRunner.java:220)    at
> org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
>   at
> org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
>   at
> org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
>   at
> org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
>   at
> org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
>   at
> org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
> Caused by: org.hibernate.exception.ConstraintViolationException: could
> not execute native bulk manipulation query    at
> org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
>   at
> org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
>   at
> org.hibernate.engine.query.NativeSQLQueryPlan.performExecuteUpdate(NativeSQLQueryPlan.java:219)
>   at
> org.hibernate.impl.SessionImpl.executeNativeUpdate(SessionImpl.java:1300)
>   at
> org.hibernate.impl.SQLQueryImpl.executeUpdate(SQLQueryImpl.java:365)
>   at
> org.hibernate.ejb.QueryImpl.internalExecuteUpdate(QueryImpl.java:183)
>   at
> org.hibernate.ejb.AbstractQueryImpl.executeUpdate(AbstractQueryImpl.java:99)
>   ... 27 more Caused by: org.h2.jdbc.JdbcSQLException: Referential
> integrity constraint violation: "FKE7E9BF09F9FEB38B:
> PUBLIC.""Attendance"" FOREIGN KEY(STUDENT) REFERENCES
> PUBLIC.""Student""(""studentId"")"; SQL statement: delete from
> "Student" [23003-135]     at
> org.h2.message.DbException.getJdbcSQLException(DbException.java:327)
>   at org.h2.message.DbException.get(DbException.java:167)     at
> org.h2.message.DbException.get(DbException.java:144)  at
> org.h2.constraint.ConstraintReferential.checkRow(ConstraintReferential.java:378)
>   at
> org.h2.constraint.ConstraintReferential.checkRowRefTable(ConstraintReferential.java:395)
>   at
> org.h2.constraint.ConstraintReferential.checkRow(ConstraintReferential.java:275)
>   at org.h2.table.Table.fireConstraints(Table.java:788)   at
> org.h2.table.Table.fireAfterRow(Table.java:805)   at
> org.h2.command.dml.Delete.update(Delete.java:79)  at
> org.h2.command.CommandContainer.update(CommandContainer.java:70)  at
> org.h2.command.Command.executeUpdate(Command.java:199)    at
> org.h2.jdbc.JdbcPreparedStatement.executeUpdateInternal(JdbcPreparedStatement.java:141)
>   at
> org.h2.jdbc.JdbcPreparedStatement.executeUpdate(JdbcPreparedStatement.java:127)
>   at
> org.hibernate.engine.query.NativeSQLQueryPlan.performExecuteUpdate(NativeSQLQueryPlan.java:210)
>   ... 31 more

您能帮我确定为什么会发生这些错误吗？我尝试了所有我能想到的办法，但收效甚微。任何帮助将不胜感激。

您尝试在删除出勤之前从数据库中删除所有学生。但出勤率对学生来说有一把外键。因此，如果数据库允许您删除学生，您将得到一个不连贯的数据库：出勤引用不存在的学生。

因此，您必须先删除考勤，然后再删除学生。

请注意，实体之间存在的级联是无关紧要的，因为插入、更新和删除查询完全忽略它们。