java - JPA中表之间的关系是如何设置的？

Question

我收到错误:

Unknown column 'employee0_2_.employee_id' in 'field list'

我的字段有什么问题？缺少什么？

完整堆栈跟踪:

Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1387)
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1310)
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1316)
at org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:898)
at tests.ApplTest.main(ApplTest.java:38)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:82)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:61)
at org.hibernate.loader.Loader.getResultSet(Loader.java:2040)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1837)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1816)
at org.hibernate.loader.Loader.doQuery(Loader.java:900)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:342)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:312)
at org.hibernate.loader.Loader.loadEntity(Loader.java:2121)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:82)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:72)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:3927)
at org.hibernate.event.internal.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:460)
at org.hibernate.event.internal.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:429)
at org.hibernate.event.internal.DefaultLoadEventListener.load(DefaultLoadEventListener.java:206)
at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:262)
at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:150)
at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1092)
at org.hibernate.internal.SessionImpl.access$2000(SessionImpl.java:175)
at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.load(SessionImpl.java:2476)
at org.hibernate.internal.SessionImpl.get(SessionImpl.java:992)
at org.hibernate.event.internal.DefaultMergeEventListener.entityIsDetached(DefaultMergeEventListener.java:271)
at org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:151)
at org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:76)
at org.hibernate.internal.SessionImpl.fireMerge(SessionImpl.java:914)
at org.hibernate.internal.SessionImpl.merge(SessionImpl.java:898)
at org.hibernate.internal.SessionImpl.merge(SessionImpl.java:902)
at org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:889)
... 6 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'employee0_2_.employee_id' in 'field list'
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
at com.mysql.jdbc.Util.getInstance(Util.java:381)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3491)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3423)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1936)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2542)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1734)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1885)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:56)

MySql 表:

CREATE TABLE Employee(employee_id INTEGER PRIMARY KEY NULL , name VARCHAR(50) UNIQUE NULL , salary VARCHAR(50) null , specialization VARCHAR(50) NULL);
CREATE TABLE Managers(name  VARCHAR(50) NULL UNIQUE , lastname VARCHAR(50) NULL UNIQUE , manager_id INTEGER NULL PRIMARY KEY AUTO_INCREMENT, FOREIGN KEY (manager_id) REFERENCES Employee(employee_id) );
CREATE TABLE Department (department_id INTEGER PRIMARY KEY AUTO_INCREMENT ,name VARCHAR(50) UNIQUE NULL , FOREIGN KEY (department_id) REFERENCES Managers(manager_id));

员工:

@Entity
@Table (name = "employee")
@Inheritance(strategy = InheritanceType.JOINED)
public class Employee{

public Employee(int id, String name, double salary, String specialization) {
    this.employee_id = id;
    this.name = name;
    this.salary = salary;
    this.specialization = specialization;
}

@Override
public String toString() {
    return "Employee{" +
            "id=" + employee_id +
            ", name='" + name + '\'' +
            ", salary=" + salary +
            ", deg='" + specialization + '\'' +
            '}';
}

public int getId() {
    return employee_id;
}

public void setId(int id) {
    this.employee_id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public double getSalary() {
    return salary;
}

public void setSalary(double salary) {
    this.salary = salary;
}

public String getSpecialization() {
    return specialization;
}

public void setSpecialization(String specialization) {
    this.specialization = specialization;
}

@Id
@Column(name = "employee_id")
private int employee_id;

@Column(name = "name")
private String name;
@Column(name = "salary")
private double salary;
@Column (name = "specialization")
private String specialization;

public Employee(){}
}

部门:

@Table(name = "department")
@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class Department extends Managers{

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public Department(String name) {
    this.name = name;
}

public Managers getManager() {
    return manager;
}

public void setManager(Managers manager) {
    this.manager = manager;
}

@OneToOne
@JoinColumn(name = "department_id" , referencedColumnName = "manager_id", insertable = false, updatable = false)
private Managers manager;

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

public int getDepartment_id() {
    return department_id;
}

public void setDepartment_id(int department_id) {
    this.department_id = department_id;
}

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

public Department(){}

}

经理:

@Table(name = "managers")
@Entity
public class Managers extends Employee{

@OneToOne
@JoinColumn(name = "manager_id", referencedColumnName = "employee_id" , insertable = false, updatable = false)
private Employee employee;

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getLastname() {
    return lastname;
}

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

public Managers(String name, String lastname) {
    this.name = name;
    this.lastname = lastname;
}

public Managers(){}

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

public int getManager_id() {
    return manager_id;
}

public void setManager_id(int manager_id) {
    this.manager_id = manager_id;
}

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

}

持久性.xml:

   <?xml version="1.0" encoding="UTF-8"?>
   <persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
   http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">

<persistence-unit name="EmployeesTesting" transaction-type="RESOURCE_LOCAL">

    <provider>org.hibernate.ejb.HibernatePersistence</provider>

    <class>employee.Employee</class>
    <class>department.Department</class>
    <class>managers.Managers</class>

    <properties>
        <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/employees"/>
        <property name="javax.persistence.jdbc.user" value="root"/>
        <property name="javax.persistence.jdbc.password" value="****"/>
        <property name="javax.persistence.jdbc.Driver" value="com.mysql.jdbc.Driver"/>
    </properties>

</persistence-unit>

主要:

public static void main(String[] args) {

    System.out.println("In the main");
    EntityManagerFactory emfactory =   Persistence.createEntityManagerFactory("EmployeesTesting");
    EntityManager entityManager = emfactory.createEntityManager();

    Employee employee = new Employee(1000,"Maks",3500,"Programmer");
    Managers manager = new Managers("maks","Burkov");
    Department department = new Department("Programmers");

     if(entityManager.contains(employee)){
        System.out.println("In the contains , the object has persistence state! ");
        entityManager.getTransaction().begin();
        entityManager.persist(employee);
        entityManager.persist(manager);
        entityManager.persist(department);
        entityManager.getTransaction().commit();
        entityManager.close();
        emfactory.close();
        System.out.println("Data Inserted!");
    }

    else if (!(entityManager.contains(employee))){
        System.out.println("In the not contains, the object is detached! ");
        entityManager.getTransaction().begin();
        entityManager.merge(employee);
        entityManager.merge(manager);
        entityManager.merge(department);
        entityManager.getTransaction().commit();
        entityManager.close();
        emfactory.close();
        System.out.println("Data Inserted!");
    }

    System.out.println("Get out from main");
  }
}

Answer 1

已更新

我已经根据您的配置做了一些测试，这是您需要做的才能实现它:

第一步

• 从实体定义中删除 @Inheritance(strategy = InheritanceType.JOINED) 注解。
• 从 Managers 和 Departments 中删除 extends

第二步

@OneToOne 映射应如下所示

员工:

@Entity
public class Employee {

    @Id
    @Column(name = "employee_id")
    private Integer employeeId;

    @OneToOne(mappedBy = "employee")
    private Manager manager;

经理:

@Entity

public class Manager {

    @Id
    @Column(name = "manager_id")
    private Integer managerId;

    @MapsId
    @OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumn(name = "manager_id", referencedColumnName = "employee_id")
    private Employee employee;

部门:

@Entity
public class Department {

    @Id
    @Column(name = "department_id")
    private Integer departmentId;

    @MapsId
    @OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumn(name = "department_id", referencedColumnName = "manager_id")
    private Manager manager;

不要忘记 getter 和 setter..

第三步

为了正确保存所有实体，使它们都具有一个共享 ID，您必须仅保存部门..它看起来像这样:

        Employee emp = new Employee();
        emp.setEmployeeId(1);
        emp.setName("employee");

        Manager manager = new Manager();
        manager.setEmployee(emp);
        manager.setName("manager");

        Department department = new Department();
        department.setName("department");
        department.setManager(manager);

        em.persist(department);

提交事务后，所有三个实体的主键都将设置为 1。