java - Hibernate mappedBy 和@JoinColumn

Question

当我尝试获得一对多和多对一关系时，车辆表上的连接列出现问题。为什么 hibernate 正在搜索列 USER_ID 而不是将其连接到表中？我知道加入的目的，但是当我尝试将它与映射的 By 属性一起使用时，我得到了这个错误。该代码有什么问题？

我得到的异常:

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'USER_ID' in 'field list'

用户表:

@Entity
@Table(name = "users")
public class User {

public User(){}

public int getId() {
    return id;
}

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

public String getFirst_name() {
    return first_name;
}

public void setFirst_name(String first_name) {
    this.first_name = first_name;
}

public int getSalary() {
    return salary;
}

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

public String getLast_name() {
    return last_name;
}

public void setLast_name(String last_name) {
    this.last_name = last_name;
}

@Override
public String toString() {
    return "User{" +
            "id=" + id +
            ", first_name='" + first_name + '\'' +
            ", salary=" + salary +
            ", last_name=" + last_name +
            '}';
}

public Collection<Vehicle> getVehicles() {
    return vehicles;
}

public void setVehicles(Collection<Vehicle> vehicles) {
    this.vehicles = vehicles;
}

@OneToMany(mappedBy = "user")
private Collection<Vehicle> vehicles = new ArrayList<>();

public Collection<Address> getAddresses() {
    return addresses;
}
public void setAddresses(Collection<Address> addresses) {
    this.addresses = addresses;
}

    @ElementCollection // for saving the collection or persist it to database
    @JoinTable(joinColumns = @JoinColumn(name = "fk_user_id")) // will add to the fk created table renamed column "fk_user_id"
    private Collection<Address> addresses = new ArrayList<>();

    @Id
    @Column(name = "user_id")
    private int id;
    @Column(name = "first_name")
    private String first_name;
    @Column(name = "salary")
    private int salary;
    @Column(name = "last_name")
    private String last_name;
 }

车辆:

@Entity
@Table(name = "vehicle")
public class Vehicle {

public User getUser() {
    return user;
}

public void setUser(User user) {
    this.user = user;
}

@ManyToOne
@JoinColumn(name = "USER_ID")
private User user;

public int getVehicle_id() {
    return vehicle_id;
}

public void setVehicle_id(int vehicle_id) {
    this.vehicle_id = vehicle_id;
}

public String getVehicle_name() {
    return vehicle_name;
}

public void setVehicle_name(String vehicle_name) {
    this.vehicle_name = vehicle_name;
}

@Id
private int vehicle_id;
private String vehicle_name;

}

Answer 1

你对待 @JoinColumn 的方式与你想象的有点不同。

当你有配置时:

public class Vehicle {

  @ManyToOne
  @JoinColumn(name = "USER_ID")
  private User user;

当 VEHICLE 和 USERS 表连接时，它告诉持久性提供程序使用 VEHICLE.USER_ID 列。

默认情况下，在 USERS 表端，使用主键，在本例中是具有相同名称的列:USERS.USER_ID(除非您指定在 @JoinColumn 中显式 referencedColumnName 属性)。

最重要的是，您的 VEHICLE 表中需要有一个 user_id 列。