Spring JPA创建问题

小编典典

Spring JPA创建问题

spring-boot

我正在尝试创建一个“游戏”，这只是为了学习，我想知道如何像研究游戏那样使用JPA进行创建的好方法，例如：

我主要有这些类/表

Question : text, description, set<Answer>, difficulty, userWhoCreated, Topic
Topic : name, set<question>
SubTopic : name, set<question>
Answer : text, question (to reference to it)
Quiz : set<question>, name, description

但是到那时，我想拥有一个存储所有这些问题的存储库，因此，当用户想要学习一点点内容时，只需从该存储库中获取问题即可。

例如，主题和子主题的目的是在用户想要问题时将其过滤掉。

例

问题：什么是加入？主题将是数据库，子主题将是联接

您能指导我如何进行此操作吗？

我的问题课的例子

@Entity(name = "question")
public class Question extends DateAudit {
    @Id
    @Column(name = "question_id")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "question_seq")
    @SequenceGenerator(name = "question_seq", allocationSize = 1)
    private Long id;

    @Column(name = "name")
    @NotBlank(message = "Question name can not be blank")
    private String name;

    @Column(name = "is_exam_question", nullable = false)
    private Boolean is_exam_question;

    @ManyToOne(fetch = FetchType.EAGER, cascade = { CascadeType.PERSIST, CascadeType.MERGE })
    private Set<Answer> answers = new HashSet<>();

}

示例答案实体

@Entity(name = "answer")
public class Answer extends DateAudit {

    @Id
    @Column(name = "answer_id")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "answer_seq")
    @SequenceGenerator(name = "answer_seq", allocationSize = 1)
    private Long id;

    @Column(name = "answer_to_question")
    @NotBlank(message = "Answer to question name can not be blank")
    private String answer_to_question;

    @ManyToOne
    private Question question;

    @Column(name="type_answer")
    private AnswerType answerType;
}

我也看到我无法创建“ TRUE / FALSE”，“ YES / NO”，“ Small description”，“ MULTI-
CHOICE”之类的答案，该如何处理？

阅读 344

2020-05-30

共1个答案

小编典典

因此，主题可以是“自引用”实体，即可以具有可选的父主题和可选的子主题集合。

主题可以嵌套到任何级别：TopicA> TopicA_1> Topic_A_1_1等。

通过在Topic中编写一个递归函数，我们可以走到树上，并在层次结构中任何级别的Topic上获取该主题及其所有子主题的问题。

话题：

Entity
@Table(name = "topics")
public class Topic{

    @Id
    private Long id;

    @OneToMany(mappedBy = "parent")
    private Set<Topic> subTopics;

    @ManyToOne
    @JoinColumn(name = "parent_id")
    private Topic parent;

    @OneToMany(mappedBy = "topic")
    private Set<Question> questions;

    //questions for this exact topic
    public Set<Question> getQuestions(){
        return questions;
    }

    //questions for this topic and all its sub-topics
    public Set<Question> getAllQuestions(){
        return getAllQuestions(this);
    }

    //recursive function to walk the topic tree and get all questions for each sub-topic
    private Set<Question> getAllQuestions(Topic topic){
        Set<Question> questions = new HashSet<>(topic.getQuestions());

        for(Topic subTopic : topic.getSubTopics()){
            questions.addAll(getAllQuestions(subTopic));
        )

        return  questions;
    }
}

题：

@Entity
@Table(name = "questions")
public class Question {

    @ManyToOne
    @JoinColumn(name = "topic_id")
    private Topic topic;
}

因此，通过引用某个主题，我可以只获取其直接问题，也可以获取其所有问题以及所有子主题（及其所有子主题.....）的问题。

Topic topic = topicRepository.findOne(someId);

//only questions directly linked to this topic
Set<Question> questions = topic.getQuestions();

//all questions linked to this topic and its sub-topics to *n* levels.
Set<Question> questions = topic.getAllQuestions();

2020-05-30