超过两个实体的休眠复杂查询

Posted 2023-03-23

【中文标题】超过两个实体的休眠复杂查询

【英文标题】：Hibernate complex query for more then two entity

【发布时间】：2021-03-04 18:48:08

【问题描述】：

我正在尝试进行休眠查询以搜索和过滤我的实体，但我找不到任何解决方案。我有三个有界实体。

团体实体

public class Group  

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column
    private int id;
    
    @Column
    private String name;
    
    @EqualsAndHashCode.Exclude 
    @OneToMany(cascade=CascadeType.PERSIST, CascadeType.DETACH, CascadeType.MERGE, CascadeType.REFRESH)
    @JoinTable(
            name="students_groups",
            joinColumns=@JoinColumn(name="group_id"),
            inverseJoinColumns=@JoinColumn(name="student_id")
            )
    @LazyCollection(LazyCollectionOption.FALSE)
    private List<Student> students; 

学生实体

public class Student  

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column
    private int id;
    
    @Column(name="personal_number")
    private int personalNumber;
    
    @Column(name="first_name")
    private String firstName;
    
    @Column(name="last_name")
    private String lastName;
    
    @Column
    private LocalDate birthday;
    
    @Column
    private String email;
    
    @Enumerated(EnumType.STRING)
    @Column(columnDefinition="enum('MALE','FEMALE')")
    private Gender gender;
    
    @Column
    private String address;
    
    @EqualsAndHashCode.Exclude 
    @OneToMany( cascade=CascadeType.PERSIST, CascadeType.DETACH, CascadeType.MERGE, CascadeType.REFRESH)
    @JoinTable(
            name="students_courses",
            joinColumns=@JoinColumn(name="student_id"),
            inverseJoinColumns=@JoinColumn(name="course_id")
            )
    @LazyCollection(LazyCollectionOption.FALSE)
    private List<Course> courses;
    
    public Student(int id) 
        this.id = id;
    

    public String getGender() 
        if(gender==null)
            gender = Gender.valueOf("MALE");
        return gender.toString();
    

    public void setGender(String gender) 
        if(gender==null)
                gender = "MALE";
        this.gender = Gender.valueOf(gender);
    

和课程实体

public class Course 

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column
    private int id;
    
    @Column
    private String name;
    
    @Column
    private String description;

我需要按 group.id 和 course.id 查找分组我尝试像这样进行查询

Query<Group> query = session.createQuery("from Group as g join g.students as s join s.courses as c where c.id like :courseId and g.id like :groupId", Group.class);

但它不起作用:(我将非常感谢你帮助我解决这个问题，并为我的英语不好:)

【参考方案1】：

尝试以这种方式更正您的查询：

Query<Group> query = session.createQuery("select g from Group g join g.students s join s.courses c where c.id = :courseId and g.id = :groupId", Group.class);

请注意：

您只能将like predicate 与string_expression 一起使用。

@LazyCollection 不推荐使用 TRUE 和 FALSE 值，因为您应该使用 @ElementCollection、@OneToMany 或 @ManyToMany 集合的 JPA FetchType 属性。