Java-Hibernate条件.setResultTransformer（）使用默认值初始化模型字段

Question

我是Hibernate的新手，我正尝试从数据库中获取一些数据。我不想获取完整的数据，而只是一个实体的投影。

问题是，在for循环中，当我获得ID和投影的名称时，它将获得默认值id = 0和name = null而不是id = 7和name =“ Name
8”的记录数据库中的原始实体。你知道是什么原因导致这个问题吗？for循环位于最后一个代码中。

这是学生实体

@Entity(name = "Students")
public class Student {
    @Id
    @GeneratedValue
    @Column(name = "StudentId")
    private int id;

    @Column(name = "Name", nullable = false, length = 50)
    private String name;

    @Column(name = "Grade")
    private Double grade = null;

    @ManyToOne(cascade = CascadeType.PERSIST)
    @JoinColumn(name = "FacultyId", nullable = false)
    private Faculty faculty;

    @ManyToMany(cascade = CascadeType.PERSIST)
    @JoinTable(
        joinColumns = @JoinColumn(name = "StudentId"),
        inverseJoinColumns = @JoinColumn(name = "CourseId"))
    private Collection<Course> courses;

    public Student() {
        this.courses = new HashSet<Course>();
    }

    // Setters and Getters for all fields
}

这是StudentModel

public class StudentModel {
    private  int id;
    private String name;

    public int getId() {
        return this.id;
    }

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

    public String getName() {
        return this.name;
    }

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

而我正在执行的代码

Session session = sessionFactory.openSession();
    session.beginTransaction();
    {
        Criteria criteria = session.createCriteria(Student.class);
        criteria.add(Restrictions.eq("name", "Name 8"))
                .setProjection(
                        Projections.projectionList()
                                .add(Projections.property("id"))
                                .add(Projections.property("name")))
                .setResultTransformer(
                        Transformers.aliasToBean(StudentModel.class));

        @SuppressWarnings("unchecked")
        List<StudentModel> students = criteria.list();

        for (StudentModel student : students) {
            System.out.println(student.getId());
            System.out.println(student.getName());
        }

        session.getTransaction().commit();
        session.close();
    }

Answer 1

您可能只是忘记了为投影分配别名：

Projections.projectionList()
           .add(Projections.property("id"), "id")
           .add(Projections.property("name"), "name")