查找多层子层的值（使用循环？？？）

Question

我不知道如何搜索这个，所以真的没有成功。我将从我拥有的数据类开始，

以下是培训计划实体（示例）

@Data
@Entity
@Table(name = "TRAINING_PLAN")
@JsonIgnoreProperties({"trainings"})
public class TrainingPlan {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "ID")
private Long id;

@Column(name = "CURRENT_PHASE")
private int currentPhase;

@Column(name = "PREVIOUS_TRAINING_PLAN_ID")
private Long previousTrainingPlanId;

@OneToMany(mappedBy = "trainingPlan", fetch = FetchType.LAZY)
private List<Training> trainings = new ArrayList<Training>();

以下是培训实体（示例）

@Data
@Entity
@Table(name = "TRAINING")
public class Training {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "ID")
private Long id;

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "TRAINING_PLAN_ID")
private TrainingPlan trainingPlan;

我希望我能够清楚地解释这一点，所以我在这里试图实现的是从所有以前的（培训计划）阶段获得培训。

工作原理——当创建下一个（新培训计划）计划阶段时，它会使用之前的PlanID引用旧计划，以便识别其父计划（类似的层）。

例如，如果TrainingPlan有第2阶段，我可以很容易地从第1阶段获得类似的培训：

    public List<Training> trainingsFromPreviousPhase(TrainingPlan plan, List<TrainingPlan> planList) {
    List<Training> previousPhaseTrainings = new ArrayList<Training>();

    if (plan.getPreviousTrainingPlanId() != null) {
        TrainingPlan previousPlanPhase = planList.parallelStream()
                .filter(e -> e.getId() == plan.getPreviousTrainingPlanId()).findAny().get();
        previousPhaseTrainings = previousPlanPhase.getTrainings();

}
    return previousPhaseTrainings;
}

现在的问题是，如果一个计划处于第5阶段，我需要从所有前4个阶段获得培训，这就是我陷入困境的地方，想不出一种自动循环的方法。我希望我解释的不是太难理解。欢迎任何建议或问题。

我在这里需要的是类似于：

List<List<Training>> getTrainingsFromAllPreviousPhases()

Answer 1

您可以像这样循环执行所有计划阶段：

TrainingPlan currentPlan = plan;
List<Training> allTrainings = new ArrayList<>();
while (cirrentPlan.getPreviousTrainingPlanId() != null) {
    TrainingPlan previousPlanPhase = planList.parallelStream()
        .filter(e -> e.getId() == currentPlan.getPreviousTrainingPlanId()).findAny().get();
    allTrainings.addAll(previousPlanPhase.getTrainings());
    currentPlan = previousPlanPhase;
}

然而，为了避免重复浏览计划列表以通过id找到一个，我建议将它们保存在地图中：

Map<Long, TrainingPlan> planMap = planList.stream()
    .collect(Collectors.toMap(TrainingPlan::getId, Function.identity());

然后可以简化代码（视觉上和O（n）复杂度方面）：

TrainingPlan currentPlan = plan;
List<Training> allTrainings = new ArrayList<>();
while (currentPlan.getPreviousTrainingPlanId() != null) {
    TrainingPlan previousPlanPhase = planMap.get(currentPlan.getPreviousTrainingPlanId());
    allTrainings.addAll(previousPlanPhase.getTrainings());
    currentPlan = previousPlanPhase;
}