在JPA中过滤子实体

问题描述

无论如何，有没有用jpa编写查询来过滤子实体?

Is there anyway to write a query in jpa that filters child entities?

我有这个实体:

@Entity
public class Project {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @ManyToOne(targetEntity =  Flow.class)
    private Flow flow;
}

流实体:

@Entity
public class Flow {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @OneToMany(targetEntity = Step.class)
    private List<Step> steps;
}

现在，我想获取项目及其流程，但是流程中的步骤应该在start和endtime属性上进行过滤.

Now I would like to get the project and his flow but the steps in the flow should be filtered on a start and endtime property.

我现在正在做的是找到项目，然后遍历所有步骤并过滤步骤.

What I'm doing right now is find the project and then loop trough all the steps and filter the steps.

赞:

List<Step> steps = project.getFlow().getSteps();
List<Step> filteredSteps = new ArrayList<>();
for (int i = 0; i < steps.size(); i++) {
    Step step = steps.get(i);

    if (step.getStartTime() == null || step.getEndTime() == null) {
        break;
    }

    if (step.getStartTime().isAfter(start) && step.getEndTime().isBefore(end)) {
        filteredSteps.add(step);
    }
}

步骤实体:

@Entity
public class Step {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    private String name;

    private LocalDateTime startTime;
    private LocalDateTime endTime;
}

我看不到如何在项目存储库中添加查询，该项目存储库是用于过滤子实体中步骤的原始存储库.

I don't see how I can add a query in my project repository which is a crudrepository to filter the steps in a child entity.

推荐答案

存储库中的此类功能就足够了.

Function like this in your Repository should be enough.

findByFlow_Steps_StartTimeAfterAndFlow_Steps_EndTimeBefore(Date startTime, Date endTime);

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