如何根据设计正确地将这个关系编码成多个关系

Question

我很难用H2数据库在Java中编写以下设计，我想我成功地完成了WeatherData表与位置的关系，但是我无法正确地使用WeatherData/WeatherDataTemperature关系(一对多)，这是因为在WeatherDataTemperature Hibernate类中，必须添加主键，但是正如您在我的模型中所看到的，这只是一个练习，但是我被阻止了，看到了Baeldung教程(https://www.baeldung.com/hibernate-one-to-many)，但是仍然被困住了，这是我所得到的，但现在我不能将许多温度分配给WeatherData，因为@Id是一个主键，当然不能重复，请帮助

​

​

我有以下课程：

WeatherData

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;

@Entity
public class WeatherData {

    @Id
    @GeneratedValue
    Long id;
    LocalDate date;
    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "location_id", referencedColumnName = "id")
    Location location;
    // Here is the problem im having I think
    @OneToMany(mappedBy = "weatherData")
    private java.util.Set<WeatherDataTemperature> weatherDataTemperature;

    WeatherData() {

    }

    public Long getId() {
        return id;
    }

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

    public LocalDate getDate() {
        return date;
    }

    public void setDate(LocalDate date) {
        this.date = date;
    }

    public Location getLocationId() {
        return location;
    }

    public void setLocationId(Location location) {
        this.location = location;
    }

    public Location getLocation() {
        return location;
    }

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

    public java.util.Set<WeatherDataTemperature> getWeatherDataTemperature() {
        return weatherDataTemperature;
    }

    public void setWeatherDataTemperature(java.util.Set<WeatherDataTemperature> weatherDataTemperature) {
        this.weatherDataTemperature = weatherDataTemperature;
    }

}

Location

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Location {

    @Id
    @GeneratedValue
    Long id;
    Double lat;
    Double lon;
    String city;
    String state;

    @OneToOne(mappedBy = "location")
    private WeatherData weatherData;

    Location() {

    }

    public Long getId() {
        return id;
    }

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

    public Double getLat() {
        return lat;
    }

    public void setLat(Double lat) {
        this.lat = lat;
    }

    public Double getLon() {
        return lon;
    }

    public void setLon(Double lon) {
        this.lon = lon;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }

    public WeatherData getWeatherData() {
        return weatherData;
    }

    public void setWeatherData(WeatherData weatherData) {
        this.weatherData = weatherData;
    }

}

WeatherDataTemperature

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;

@Entity
public class WeatherDataTemperature implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    @Id
    @ManyToOne
    @JoinColumn(name = "weather_data_id", nullable = false)
    private WeatherData weatherData;
    Double temperature;

    WeatherDataTemperature() {

    }

    public WeatherData getWeatherData() {
        return weatherData;
    }

    public void setWeatherData(WeatherData weatherData) {
        this.weatherData = weatherData;
    }

    public Double getTemperature() {
        return temperature;
    }

    public void setTemperature(Double temperature) {
        this.temperature = temperature;
    }

}

编辑

有什么方法可以让它像设计一样工作吗？在温度表中没有主键的情况下，这里还有一个JSON，说明它的外观(温度可以为单个WeaterData存储多达4个不同的值)：

{
    "id": 37892,
    "date": "2020-09-15",
    "location": {
        "lat": 32.7767,
        "lon": 96.7970,
        "city": "Dallas",
        "state": "Texas"
    },
    "temperature": [
        89.7,
        84.3,
        91.2,
        93.1
    ]
}

Answer 1

显然，要使此工作完全符合设计的要求，我必须使用@ElementCollection，如下所示：

WeatherData

import java.time.LocalDate;

import javax.persistence.CascadeType;
import javax.persistence.CollectionTable;
import javax.persistence.ElementCollection;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;

@Entity
public class WeatherData {

    @Id
    @GeneratedValue
    Long id;
    LocalDate date;
    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "location_id", referencedColumnName = "id")
    Location location;

    @ElementCollection
    @CollectionTable(name = "Weather_Data_Temperature")
    private java.util.Set<Double> temperature;

    WeatherData() {

    }

    public Long getId() {
        return id;
    }

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

    public LocalDate getDate() {
        return date;
    }

    public void setDate(LocalDate date) {
        this.date = date;
    }

    public Location getLocationId() {
        return location;
    }

    public void setLocationId(Location location) {
        this.location = location;
    }

    public Location getLocation() {
        return location;
    }

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

}

位置类没有更改

WeatherDataTemperature类磁盘(如果使用@ElementCollection则不需要)

因此，当运行项目时，h2数据库将生成良好，如下所示：

​

​

请注意，我能够插入两个不同的温度，但两者都有相同的weather_data_id，就像设计建议的那样，可以不需要主键。