Question

我有CrudRepository个实体。

问题：特征实体始终在数据库中创建其他ID字段，但未选择正确的characteristic_id字段来生成JSON。

机器实体

machine_id || name || description

特色实体

characteristic_id || machine_id || name || description || type || value

问题：为什么特征实体始终会创建名为id的ID字段，而不使用定义的字段characteristic_id？

JSON

实体如何操纵数据库布局：

机器实体

@Entity

@Table（name =＆＃34; maschine＆＃34;）公共类机器{ private int machine_id;

private String name;

private String description; 

private Set<Characteristic> characteristics;

@OneToMany(fetch = FetchType.EAGER, mappedBy = "machine", cascade = CascadeType.ALL)
public Set<Characteristic> getCharacteristics() {
    return characteristics; 
}

public void setCharacteristics(Set<Characteristic> characteristics){
    this.characteristics = characteristics;
}

public Machine(){}

public Machine(String name, String description){
    this.name = name;
    this.description = description; 
}

@Override
public String toString() {
    return "Machine [id=" + machine_id + ", name=" + name + ", description=" + description + "]";
}

@Id 
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name="id")
public int getId() {
    return machine_id;
}

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

@Column(name="name")
public String getName() {
    return name;
}

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

@Column(name="description")
public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

}

特色实体

@Entity

@Table（名字=＆＃34;特色＆＃34;）公共阶层特征{ private int characteristic_id;

private String name; 

private String description; 

private int type; 

private int value;

private Machine machine; 

@ManyToOne
@JoinColumn(name="machine_id")
public Machine getMachine(){
    return machine;
}

public void setMachine(Machine machine){
    this.machine = machine;
}

public Characteristic() {} 

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name="id")
public int getCharacteristic_Id() {
    return characteristic_id;
}

public void setCharacteristic_Id(int characteristic_id) {
    this.characteristic_id = characteristic_id;
}

@Column(name="name")
public String getName() {
    return name;
}

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

@Column(name="description")
public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

@Column(name="type")
public int getType() {
    return type;
}

public void setType(int type) {
    this.type = type;
}

@Column(name="value")
public int getValue() {
    return value;
}

public void setValue(int value) {
    this.value = value;
}

@Override
public String toString() {
    return "Characteristic [id=" + characteristic_id + ", name=" + name + ", description=" + description + ", type=" + type
            + ", value=" + value + "]";
}

}

我的CrudRepository与数据库交互：

public interface MachineRepository extends CrudRepository<Machine, Integer>{

}

我的控制器：

@RestController
public class HomeController {

    private final MachineRepository machineRepository;

    @Autowired
    HomeController(MachineRepository machineRepository) {
        this.machineRepository = machineRepository;
    }

    @RequestMapping(value = "/machine", method = RequestMethod.GET)
    Collection<Machine> readMachines(){
        return (Collection<Machine>) machineRepository.findAll();
    }

}

这是我为数据库操作编写的所有代码..

Answer 1

默认情况下，由于您未在配置中指定列名，因此hibernate将使用getter方法的名称，而不使用“get”部分作为表中的列名。以下是特征实体

中的配置

@Id
@GeneratedValue
public int getId() {
    return characteristic_id;
}

由于您没有为memeber characteristic_id指定任何显式列名，因此默认情况下，hibernate选择Id（从getId（）方法中删除get）作为成员的列名。因此，它总是为您的characteristics_id成员创建一个名为Id的列。

为了强制hibernate使用characteristic_id作为列名，可以使用@Column注释并将列名提供为characteristics_id 除了用于标记吸气剂的@Id和@GeneratedValue之外。

@Id
@GeneratedValue
@Column(name="characteristic_id")
public int getId() {
    return characteristic_id;
}

或者您可以更改getter和setter的名称，如下所示

@Id
@GeneratedValue
public int getCharacterisitc_id() {
    return characteristic_id;
}

public void setCharacterisitc_id(int characteristic_id) {
    this.characteristic_id = characteristic_id;
}

Answer 2

更改为此代码

@Id
@GeneratedValue
@Column(name="id", nullable = false)
public int getCharacteristic_id() {
    return characteristic_id;
}

实体创建无用的id字段

2 个答案: