SpringBoot 不会在实体中保存 Set

Question

My TimeTrail class has a Set of TimeTrailStage. After i do a save, if i query the object, the timetrail_id on stage is null. So the stages are empty. I do not know what i'm doing wrong. i have looked in to the OneToMany/ManyToOne relationship, but as far as i can see it's correct.

TimeTrail.class

package com.verhees.cm.model.competition;

import com.verhees.cm.model.stage.TimeTrialStage;
import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import lombok.experimental.SuperBuilder;

import javax.persistence.Entity;
import javax.persistence.OneToMany;
import java.util.Set;

@Entity
@NoArgsConstructor
@AllArgsConstructor
@SuperBuilder
@Getter
@Setter
public class TimeTrail extends Competition {
    @OneToMany(mappedBy = "competitie")
    private Set<TimeTrialStage> stages;
}

Competition.class

package com.verhees.cm.model.competition;

import lombok.*;
import lombok.experimental.SuperBuilder;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.validation.constraints.Size;

@Entity
@SuperBuilder
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
public abstract class Competition {
    @Id
    @Size(min = 3, max = 15)
    private String name;
}

TimeTrailStage.class

public class TimeTrialStage extends Stage {

    @ManyToOne
    @JoinColumn(name="timetrail_id", nullable = false)
    private TimeTrail competitie;

    @ManyToMany
    @JoinTable(
            name = "team_stage",
            joinColumns = @JoinColumn(name = "stage_id"),
            inverseJoinColumns = @JoinColumn(name = "team_id"))
    private List<Team> teams = new ArrayList<>();

    @OneToMany(cascade = CascadeType.ALL)
    private List<Score> scores;

    @OneToMany(cascade = CascadeType.ALL)
    private List<TimeTrialStagePrediction> predictions;

}

Stage.class

package com.verhees.cm.model.stage;

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import lombok.experimental.SuperBuilder;

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

import java.util.Date;

import static javax.persistence.GenerationType.IDENTITY;

@Entity
@AllArgsConstructor
@NoArgsConstructor
@SuperBuilder
@Getter
@Setter
public abstract class Stage {
    @Id
    @GeneratedValue(strategy = IDENTITY)
    private Long id;

    private Date date;
}

Database runs on Mysql, MySQL5InnoDBDialect.

Answer 1

You should try to use @MappedSuperclass over Competition class. Right now hibernate don't know how to map id (name) to database model.

Here you can find example/documentation: https://docs.oracle.com/javaee/5/api/javax/persistence/MappedSuperclass.html