递归 ORM 类的 Spring Repository 性能问题

Now I am asking for every parent element (parent_id = null) with Spring Crud Repository. To do so I am using a loop that is iterating over a list with all parent-element-ids and calling findOne(parentelementid) for every parent element id and using LAZY Loading:

List<Skill> parentList = skillDAO.findBySkill(null);
HashMap<Integer, ArrayList<Integer>> parentTree = customSkillDAO.findParentIdsByPersonSkills(listPersonskill);

    //Integer: Durchnummeriert zur Eindeutigkeit, von 0,1,2...
    //List: Pfad vom höchsten Vaterlement zum niedrigsten Personskill
    //Notwendig, um den Pfad pro niedrigsten Knoten auf true zu setzen
    HashMap<Integer, ArrayList<Integer>> parentTree = customSkillDAO.findParentIdsByPersonSkills(listPersonskill);
    log.info("START FINDING CHECKED");
//keySet is just numbered from 0,1,2,3...
for (int counter : parentTree.keySet()) {
        //parentTree.get(counter) gives a list whith Integer that describes the path from top to bottom.
        //So the first element is always the parent.
        mapParentSkills.put(parentTree.get(counter).get(0), new SkillDTO(skillDAO.findOne(parentTree.get(counter).get(0))));
        mapParentSkills.get(parentTree.get(counter).get(0)).setChecked(true);
    }
    log.info("START FINDING NOT CHECKED");
//Add all other parent that are not checked
for (Skill skill : parentList) {
        if (!mapParentSkills.containsKey(skill.getIdSkill())) {
            mapParentSkills.put(skill.getIdSkill(), new SkillDTO(skill));
        }
    }

    log.info("ENDE SKILLS");

我得到了整棵树，这很好.唯一的问题是它需要大约 10 秒.谁能告诉我一些建议来改进它以至少在 <2 秒内完成它?

public class Skill implements java.io.Serializable {

    public Skill() {
}


@Id
@GeneratedValue(strategy = IDENTITY)

@Column(name = "idSkill", unique = true, nullable = false)
public Integer getIdSkill() {
    return this.idSkill;
}

public void setIdSkill(Integer idSkill) {
    this.idSkill = idSkill;
}

@JsonBackReference
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "parent_id")
public Skill getSkill() {
    return this.skill;
}

public void setSkill(Skill skill) {
    this.skill = skill;
}

@JsonManagedReference
@OneToMany(fetch = FetchType.LAZY, mappedBy = "skill")
public Set<Skill> getSkills() {
    return this.skills;
}

public void setSkills(Set<Skill> skills) {
    this.skills = skills;
}

}

public SkillDTO(Skill skill) {
    idSkill = skill.getIdSkill();
    name = skill.getName();
    levelBezeichnung = skill.getLevelBezeichnung().getBezeichnung();
    checked = skill.isChecked();
    if (skill.getSkills().size() > 0) {
        Iterator<Skill> iteratorSkill = skill.getSkills().iterator();
        while (iteratorSkill.hasNext()) {
            Skill tempSkill = iteratorSkill.next();
            skills.add(convertSkillsToProfileDTO(tempSkill));
        }
    }
}

private SkillDTO convertSkillsToProfileDTO(Skill skill) {
    return new SkillDTO(skill);
}