在使用Hibernate时，我遇到了这个错误

@JoinColumn

org.hibernate.exception.SQLGrammarException: 无法执行语句 [Unknown column 'department_id' in 'field list'] [insert into employees (department_id,hire_date,name,position,salary) values (?,?,?,?,?)]

我在使用关联列，以为在连接表时，department_id这个别名会被生成并作为外键。

我有两个实体和两张表。第一张表名为employees

CREATE TABLE employees (
    id INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
    name VARCHAR(50),
    position VARCHAR(50),
    salary DECIMAL(10, 2),
    hire_date DATE
);

以及对应的实体

package codefinity.model;

import jakarta.persistence.*;
import lombok.*;

import java.util.Date;


@Entity
@Table(name = "employees")
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

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

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

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

    @Column(name = "hire_date")
    private Date hireDate;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "department_id")
    private Department department;

    public Employee() {
    }

    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 getPosition() {
        return position;
    }

    public void setPosition(String position) {
        this.position = position;
    }

    public double getSalary() {
        return salary;
    }

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

    public Date getHireDate() {
        return hireDate;
    }

    public void setHireDate(Date hireDate) {
        this.hireDate = hireDate;
    }

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }
}

第二张表

CREATE TABLE departments (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    location VARCHAR(100)
);

以及对应的实体

package codefinity.model;

import jakarta.persistence.*;

@Entity
@Table(name ="departments")
public class Department {

    public Department() {
    }

    public Department(String name, int id, String location) {
        this.name = name;
        this.id = id;
        this.location = location;
    }
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

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

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

    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 getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }

}

Hibernate配置文件

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration SYSTEM
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!--  JDBC set up-->
        <property name="hibernate.connection.driver_class">com.mysql.cj.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/testDatabase</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">1234</property>

        <!-- Dialect setup -->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

        <!-- SQL Display and Formatting Settings -->
        <property name="show_sql">true</property>
        <property name="format_sql">true</property>

        <property name="hibernate.current_session_context_class">thread</property>
    </session-factory>
</hibernate-configuration>

下面是失败的测试方法

@Test
public void testEmployeeEntityMapping() {
    Department department = new Department();
    department.setName("Development");
    department.setLocation("Main Office");
    session.persist(department);

    Employee employee = new Employee();
    employee.setName("John Doe");
    employee.setPosition("Developer");
    employee.setSalary(75000);
    employee.setHireDate(new Date());
    employee.setDepartment(department);
    session.persist(employee);

    session.flush();
    session.clear();

    Employee retrievedEmployee = session.get(Employee.class, employee.getId());
    assertNotNull(retrievedEmployee, "Employee was not retrieved, mapping may be incorrect.");
    assertNotNull(retrievedEmployee.getDepartment(), "Department of the retrieved employee is null, association mapping may be incorrect.");
}

是配置有问题吗，还是Join没有为department_id创建别名？

我的pom.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>codefinity</groupId>
    <artifactId>Hibernate_Entity_Creation_Task</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>21</maven.compiler.source>
        <maven.compiler.target>21</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.hibernate.orm/hibernate-core -->
        <dependency>
            <groupId>org.hibernate.orm</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>6.3.1.Final</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.46</version>
            <scope>compile</scope>
        </dependency>

        <!-- JUnit 5 Jupiter API -->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>5.8.2</version>
            <scope>test</scope>
        </dependency>

        <!-- JUnit 5 Jupiter Engine -->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-engine</artifactId>
            <version>5.8.2</version>
            <scope>test</scope>
        </dependency>

        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.33</version>
        </dependency>
    </dependencies>
</project>

解决方案

org.hibernate.exception.SQLGrammarException: 无法执行语句 [Unknown column 'department_id' in 'field list'] [insert into employees (department_id,hire_date,name,position,salary) values (?,?,?,?,?)]

此错误表示你向未知字段插入了：department_id。因为 employees.id 是 employees 表的主键。你需要在 employees 表中新增一个名为 department_id 的列，作为对 departments.id 的外键引用。