将 SQL 查询转换为 HQL 时出错，Java Hibernate

Question

我有一个 Spring MVC + JDBC 应用程序。我在大学的数据库和 GroupDao 中有 LectureDao 类的讲座和小组表。现在我正在尝试用 Hibernate 替换 JDBC。我有一个 SQL 查询

private static final String GET_ALL_GROUPS_FOR_LECTURE = "SELECT * FROM GROUPS " +
            "INNER JOIN LECTUREGROUPS ON GROUPS.ID = LECTUREGROUPS.GROUPID " +
            "WHERE LECTUREID = ?";

现在我已经像这样将它转换成 HQL

private static final String GET_ALL_GROUPS_FOR_LECTURE = "FROM Group " +
            "JOIN LectureGroup ON Group.id = LectureGroup.groupId " +
            "WHERE LectureGroup.lectureId = :lectureId";

我有使用这个查询的方法

public List<Group> getGroupsOnLecture(int lectureId) {
    try (Session session = sessionFactory.openSession()) {
        Transaction transaction = session.beginTransaction();
        Query<Group> query = session.createQuery(GET_ALL_GROUPS_FOR_LECTURE, Group.class);
        query.setParameter("lectureId", lectureId);
        List<Group> groupsOnLecture = query.list();
        transaction.commit();
        return groupsOnLecture;
    }
}

我运行我的应用程序出现异常。错误显示在这个带有 queryCreation 的原始文件中。所以HQL语法错误。我做错了什么？

这是 Lecture and Group 和 LectureGroup Entites

@Entity
@Table(name = "groups")
public class Group {

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

    public Group(String name, int streamId) {
        this.name = name;
        this.streamId = streamId;
    }

    public Group() {
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }

    public String getStringId() {
        return String.valueOf(id);
    }

    public int getStreamId() {
        return streamId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setStreamId(int streamId) {
        this.streamId = streamId;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Group group = (Group) o;
        return id == group.id &&
                streamId == group.streamId &&
                name.equals(group.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, name, streamId);
    }

    @Override
    public String toString() {
        return "Group{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", streamId=" + streamId +
                '}';
    }

}

@Entity
@Table(name = "lectures")
public class Lecture {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private int id;
    @Column(name = "subjectId")
    private int subjectId;
    @Column(name = "professorId")
    private int professorId;
    @Column(name = "date")
    @DateTimeFormat(pattern = "yyyy-MM-dd")
    private LocalDate date;
    @Column(name = "time")
    @DateTimeFormat(pattern = "HH:mm")
    private LocalTime time;
    @Column(name = "classroomId")
    private int classroomId;

    public Lecture(int subjectId, int professorId, LocalDate date, LocalTime time, int classroomId) {
        this.subjectId = subjectId;
        this.professorId = professorId;
        this.date = date;
        this.time = time;
        this.classroomId = classroomId;
    }

    public Lecture() {
    }

    public int getId() {
        return id;
    }

    public int getSubjectId() {
        return subjectId;
    }

    public int getProfessorId() {
        return professorId;
    }

    public LocalDate getDate() {
        return date;
    }

    public String getDateString() {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-uuuu");
        return date.format(formatter);
    }

    public LocalDate setDateFromString(String dateString) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-uuuu");
        return LocalDate.parse(dateString, formatter);
    }

    public LocalTime getTime() {
        return time;
    }

    public int getClassroomId() {
        return classroomId;
    }

    public void setId(int id) {
        this.id = id;
    }

    public void setSubjectId(int subjectId) {
        this.subjectId = subjectId;
    }

    public void setProfessorId(int professorId) {
        this.professorId = professorId;
    }

    public void setDate(LocalDate date) {
        this.date = date;
    }

    public void setTime(LocalTime time) {
        this.time = time;
    }

    public void setClassroomId(int classroomId) {
        this.classroomId = classroomId;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Lecture lecture = (Lecture) o;
        return id == lecture.id &&
                subjectId == lecture.subjectId &&
                professorId == lecture.professorId &&
                classroomId == lecture.classroomId &&
                date.equals(lecture.date) &&
                time.equals(lecture.time);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, subjectId, professorId, date, time, classroomId);
    }

    @Override
    public String toString() {
        return "Lecture{" +
                "id=" + id +
                ", subjectId=" + subjectId +
                ", professorId=" + professorId +
                ", date=" + date +
                ", time=" + time +
                ", classroomId=" + classroomId +
                '}';
    }

}

@Entity
@Table(name = "lecturegroups")
public class LectureGroup {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private int id;
    @Column(name = "lectureId")
    private int lectureId;
    @Column(name = "groupId")
    private int groupId;

    public LectureGroup(int lectureId, int groupId) {
        this.lectureId = lectureId;
        this.groupId = groupId;
    }

    public LectureGroup() {
    }

    public void setId(int id) {
        this.id = id;
    }

    public void setLectureId(int lectureId) {
        this.lectureId = lectureId;
    }

    public void setGroupId(int groupId) {
        this.groupId = groupId;
    }

    public int getId() {
        return id;
    }

    public int getLectureId() {
        return lectureId;
    }

    public int getGroupId() {
        return groupId;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        LectureGroup that = (LectureGroup) o;
        return id == that.id &&
                lectureId == that.lectureId &&
                groupId == that.groupId;
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, lectureId, groupId);
    }

    @Override
    public String toString() {
        return "LectureGroup{" +
                "id=" + id +
                ", lectureId=" + lectureId +
                ", groupId=" + groupId +
                '}';
    }
}

Answer 1

换成下面试试。原因是如果存在关系，您只能加入（Group join LectureGroup），因为您的类没有映射到像 ManyToOne 这样的关系。您必须使用如下语法，或者您可以使用适当的关系映射更改类以使用您正在尝试的语法。

private static final String GET_ALL_GROUPS_FOR_LECTURE = "select distinct g FROM Group g, LectureGroup lg WHERE g.id = lg.groupId and lg.lectureId = :lectureId";

将 SQL 查询转换为 HQL 时出错，Java Hibernate

errror in converting SQL query to HQL, Java Hibernate

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