IllegalArgumentException-休眠错误-org.hibernate.hql.internal.ast.QuerySyntaxException：未映射Clasa [从Clasa c中选择SELECT c]

问题描述

我有以下代码行，其中我尝试使用JPQL语法从类中获取所有用户： `

import javax.persistence.EntityManager;
import javax.persistence.TypedQuery;
import java.util.List;

public class ClasaDao {

    private EntityManager em;

    public ClasaDao(EntityManager em){
        this.em = em;
    }

    public List<Clasa> getClase(){

        String sql = "SELECT c FROM Clasa c";

        TypedQuery<Clasa> query = em.createquery(sql,Clasa.class);

        return query.getResultList();
    }

    public void stergeClasa(Clasa clasa){

        clasa = em.merge(clasa);
        em.remove(clasa);
    }}`

这是Entity类：

    import javax.persistence.*;
    import java.io.Serializable;
    import java.util.Date;
    import java.util.List;
    
    @Entity
    @Table(name = "Clasa")
    public class Clasa implements Serializable {
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private int id;
    
        @Temporal(value = TemporalType.DATE)
        private Date dataIncepere;
    
        private String nume;
    
        @ManyToOne
        private Curs curs;
    
        @ManyToMany(mappedBy = "clasa")
        private List<Student> student;
    
        public List<Student> getStudent() {
            return student;
        }
    
        public void setStudent(List<Student> student) {
            this.student = student;
        }
    
        public Clasa getClasa() {
            return clasa;
        }
    
        public void setClasa(Clasa clasa) {
            this.clasa = clasa;
        }
    
        private Clasa clasa;
    
        public Curs getCurs() {
            return curs;
        }
    
        public void setCurs(Curs curs) {
            this.curs = curs;
        }
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public Date getDataIncepere() {
            return dataIncepere;
        }
    
        public void setDataIncepere(Date dataIncepere) {
            this.dataIncepere = dataIncepere;
        }
    
        public String getNume() {
            return nume;
        }
    
        public void setNume(String nume) {
            this.nume = nume;
        }
    
        @Override
        public String toString() {
            return "Clasa{" +
                    "dataIncepere=" + dataIncepere +
                    ",nume='" + nume + '\'' +
                    '}';
        }
    }

上面的行产生以下错误：线程“ main”中的异常java.lang.IllegalArgumentException：org.hibernate.hql.internal.ast.QuerySyntaxException：未映射Clasa [从Clasa c中选择SELECT c]

对于可能导致此错误的原因的任何想法，将不胜感激

解决方法

似乎：

@ManyToMany(mappedBy = "clasa")

应该是：

@ManyToMany(mappedBy = "Clasa")

这可能导致IllegalArgumentException。

如果它说未映射，则该类不包含在持久性单元中。检查您是否在persistence.xml中列出了该类，或者添加了<exclude-unlisted-classes>false</exclude-unlisted-classes>

java java persistence