java - 如何使用注释保存将列表作为值的 map ？

Question

我有三个模型类:学生、工作场所、周，我尝试坚持使用 Annotations 。每个学生每周可以有多个工作场所，因此学生类(class)有一个字段 Map<Week, List<Workplace>> 。但我没有找到将其映射到数据库的解决方案。

我确实设法坚持了 @ManyToMany学生和工作场所之间的关系使用JoinTable将 Student_id、Workplace_id 和 Week_id 作为 DB 表中的列，但映射的只是一个字段 Map<Week, Workplace>在类(class)学生中。

以下是带有 Annotations 的简化模型类我上次尝试过。我得到的错误是 Use of @OneToMany or @ManyToMany targeting an unmapped class: model.Student.studentsWorkplaces[java.util.List] 。

@Entity
public class Student {
    @Id 
    private Integer id;     
    @ManyToMany
    @JoinTable(name = "STUDENTS_WORKPLACES", 
        joinColumns = @JoinColumn(name = "STUDENT"),
        inverseJoinColumns = @JoinColumn(name = "WEEK"))
    @MapKeyJoinColumn(name = "WORKPLACE")
    private Map<Week, List<Workplace>> studentsWorkplaces;
//      Getters, Setters
}

@Entity
public class Workplace {    
    @Id
    private Integer id;     
    @ManyToMany(mappedBy="studentsWorkplaces")
    private Map<Week, Student> workplaceStudents;
//      Getters, Setters
}

@Entity
public class Week {
    @Id
    private String week_year;   
    @ManyToMany(mappedBy="studentsWorkplaces")
    private List<Student> students;
    @ManyToMany(mappedBy="studentsWorkplaces")
    private List<Workplace> workplaces;
//      Getters, Setters
}

感谢您的帮助!

Answer 1

没有 JPA 不支持这一点。请参阅此文档 https://en.wikibooks.org/wiki/Java_Persistence/Relationships#Nested_Collections.2C_Maps_and_Matrices这解释了原因。

并且已经在这个问题中提出并回答了I want to map a Map<Long, List<POJO>> through JPA