Question

您好我正在使用以下代码从Employee表中查看firstName的列值，但是我遇到了以下错误：

错误：

线程“main”中的异常java.lang.ClassCastException：java.lang.String无法强制转换为com.servlet.prgm.Employee 在com.servlet.prgm.ManageEmployee.listEmployees（ManageEmployee.java:90）在com.servlet.prgm.ManageEmployee.main（ManageEmployee.java:33）

代码：

   Query sql = session.createQuery("select firstName FROM Employee");
     List employees = sql.list();
     for (Iterator iterator = employees.iterator(); iterator.hasNext(); )
         {
         Employee employee = (Employee)iterator.next();
         employee.getFirstName();
         System.out.println("First Name" +employee.getFirstName());
         }
     tx.commit();
     }catch (HibernateException e) {
     if (tx!=null) tx.rollback();
     e.printStackTrace(); 
  }finally {
     session.close(); 
  }

Employee.class

  package com.servlet.prgm;

  public class Employee {
   private int id;
   private String firstName; 
   private String lastName;   
   private int salary;  

   public Employee() {}
   public Employee(String fname, String lname, int salary) {
      this.firstName = fname;
      this.lastName = lname;
      this.salary = salary;
   }
   public Employee(String fname){
       this.firstName=fname;
   }
   public int getId() {
      return id;
   }
   public void setId( int id ) {
      this.id = id;
   }
   public String getFirstName() {
      return firstName;
   }
   public void setFirstName( String first_name ) {
      this.firstName = first_name;
   }
   public String getLastName() {
      return lastName;
   }
   public void setLastName( String last_name ) {
      this.lastName = last_name;
   }
   public int getSalary() {
      return salary;
   }
   public void setSalary( int salary ) {
      this.salary = salary;
   }
}

如果我的格式不正确，我很抱歉，我很快就会改进。

感谢您的帮助。

Answer 1

您正在选择单个标量值，因此Hibernate实际上返回了一个字符串列表：

try {
    Query sql = session.createQuery("select firstName FROM Employee");
    List firstNames = sql.list();
    for (Iterator iterator = firstNames.iterator(); iterator.hasNext(); )
    {
        string firstName = (string)iterator.next();
        System.out.println("First Name" + firstName);
    }
    tx.commit();
}catch (HibernateException e) {
    if (tx!=null) tx.rollback();
    e.printStackTrace(); 
}finally {
   session.close(); 
}

Hibernate：如何在hibernate中使用单列查看查询输出

1 个答案: