Question

我在尝试使用Hibernate执行SQL查询时遇到以下错误。

错误： -

Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to model.Emp1000
    at com.firsthb.StoreData.selectoperation_sql(StoreData.java:107)
    at com.firsthb.StoreData.main(StoreData.java:43)

Hibernate代码： -

    Query sqlquery1 = session.createSQLQuery("Select  a.id, a.firstName, a.lastName, b.emp_dept from Emp1000 a inner join emp_dept b on a.id = b.emp_id");

List<Emp1000> sqllist1 = sqlquery1.list();

for (Emp1000 emp : sqllist1) {
    System.out.println(emp.getFirstName());
}

员工持久类： -

package model;

import java.io.Serializable;
import javax.persistence.*;
import java.util.List;


/**
 * The persistent class for the emp1000 database table.
 * 
 */
@Entity
@NamedQuery(name="Emp1000.findAll", query="SELECT e FROM Emp1000 e")
public class Emp1000 implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private int id;

    private String firstName;

    private String lastName;

    //bi-directional many-to-one association to EmpDept
    @OneToMany(mappedBy="emp1000", cascade = CascadeType.MERGE)
    private List<EmpDept> empDepts;

    public Emp1000() {
    }

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

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

    public String getFirstName() {
        return this.firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return this.lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public List<EmpDept> getEmpDepts() {
        return this.empDepts;
    }

    public void setEmpDepts(List<EmpDept> empDepts) {
        this.empDepts = empDepts;
    }

    public EmpDept addEmpDept(EmpDept empDept) {
        getEmpDepts().add(empDept);
        empDept.setEmp1000(this);

        return empDept;
    }

    public EmpDept removeEmpDept(EmpDept empDept) {
        getEmpDepts().remove(empDept);
        empDept.setEmp1000(null);

        return empDept;
    }

}

问题： -

持久化类Emp1000与查询执行完全匹配。为什么我会收到错误

Answer 1

我认为EmpDept是另一个实体。

您无法使用表格Emp1000

加入实体emp_dept

尝试做类似的事情：

Select a.id, a.firstName, a.lastName, b.department from Emp1000 a inner join EmpDept b on a.id = b.id;

Answer 2

在您的查询中，您尝试获取

Select  a.id, a.firstName, a.lastName, b.emp_dept from Emp1000 a inner join emp_dept b on a.id = b.emp_id

实际上是返回两个不同对象的属性。你想要的是来自两个不同实体的自定义字段。您可以使用此

实现此目的

Query query = session.createQuery("Select  a.id, a.firstName, a.lastName, b.emp_dept from Emp1000 a inner join emp_dept b on a.id = b.emp_id");
List<Object[]> rows = query.list();

然后迭代这个Object []列表，如下所示：

for (Object[] row: rows) {
 System.out.println(" ------------------- ");
 System.out.println("id: " + row[0]);
 System.out.println("first name: " + row[1]);
 System.out.println("last name: " + row[2]);
 System.out.println("department: " + row[3]);
}

您收到此错误是因为它尝试将object []转换为特定的Entity对象。

ClassCastException - Hibernate进程结果

2 个答案: