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 courses;
public Student() {
this.courses = new HashSet();
}
// 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 students = criteria.list();
for (StudentModel student : students) {
System.out.println(student.getId());
System.out.println(student.getName());
}
session.getTransaction().commit();
session.close();
}
