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在Hibernate中尝试连接查询时获取ClassCastException

classcastexception hql hibernate java

Salahuddin Shayan · 技术社区 · 2 年前

这是我的桌子:

@Entity

@表(name=“Students”) 公立班学生{

@Id
@Column(name="Student_ID")
private int id;

@Column(name="Student_Name")
private String name;

@Column(name="Email_ID")
private String emailId;

@Column(name="Phone_no")
private long phoneNo;

@Column(name="Class_ID")
private int classId;

@Column(name="DOB")
private Date dob;

和

@实体

@表(名称=“已分配”)

@Id
@Column(name="Assign_ID")
private int aId;

@Column(name="Class_ID")
private int classId;

@Column(name="Teacher_ID")
private int tId;

@Column(name="Subject_ID")
private int sId;

PrintWriter out = response.getWriter();
    out.append("<html><body>");

    SessionFactory sf = HibernateUtil.getSessionFactory();

    Session session = sf.openSession();
    
    List<Subjects> subjects = session.createQuery(" from Subjects").list();
    
    out.println("<h1> Students List :-");
    out.println("<table>");
    
    out.println("<tr>");
    out.println("<th> Subject Id </th>");
    out.println("<th> Subject Name </th>");
    out.println("</tr>");
    
    for(Subjects subject : subjects ) {
        out.println("<tr>");
        out.println("<td>"+subject.getsId()+"</td>");
        out.println("<td>"+subject.getsName()+"</td>");
        out.println("</tr>");
    }
    out.println("</table>");
    out.append("</body></html>");

它工作得很好,但当我试着运行它时:

PrintWriter out = response.getWriter();
    out.append("<html><body>");

    SessionFactory sf = HibernateUtil.getSessionFactory();

    Session session = sf.openSession();
    
    List<Subjects> subjects = session.createQuery("from Subjects s, Assign a where s.sId = a.sId and a.classId = 2").list();
    
    out.println("<h1> Students List :-");
    out.println("<table>");
    
    out.println("<tr>");
    out.println("<th> Subject Id </th>");
    out.println("<th> Subject Name </th>");
    out.println("</tr>");
    
    for(Subjects subject : subjects ) {
        out.println("<tr>");
        out.println("<td>"+subject.getsId()+"</td>");
        out.println("<td>"+subject.getsName()+"</td>");
        out.println("</tr>");
    }
    out.println("</table>");
    out.append("</body></html>");

它给出了以下错误:

我在这里读到的时候没有做@manytone注释( How to make this select * from two joined tables query in HQL form? )你也可以在没有他们的情况下工作。

我试过各种各样的东西,但都没有用。有人能告诉我为什么会发生这种情况,以及如何解决这个问题吗?

1 回复 | 直到 2 年前

Shervin Zadsoroor 2 年前

List<Subjects> subjects = 
session.createQuery(
          "select s from Subjects s, Assign a where s.sId = a.sId and 
           a.classId = 2", Subjects.class).list();