HQL查询如何返回实体？答案

【问题标题】：HQL query how to return entity?HQL查询如何返回实体？
【发布时间】：2019-06-12 09:19:42
【问题描述】：

您好，我正在努力让这个查询成功执行。我有这 2 个实体，并且都有各自的 getter 和 setter。

@Entity
@Table(name="customer")
public class Customer {

    @Id
    @Column(name="Customer_Code")
    private String customer_Code;

    @Column(name="Customer_Name")
    private String customer_Name;
}


 @Entity
@Table(name="project")
public class Project {

    @Id
    @Column(name="Project_Code")
    public String project_Code;

    @Column(name="Project_Customer")
    public String project_Customer;

    @Column(name="Project_Description")
    public String project_Description;

    @Column(name="Project_Pastel_Prefix")
    public String project_Pastel_Prefix;

    @Column(name="Project_Name")
    public String project_Name;
}

十这是我的控制器方法：

// need to inject the session factory
    @Autowired
    private SessionFactory sessionFactory;

    @Override
    public List<Customer> getCustomers() {

        // get the current hibernate sessio
    Session currentSession = sessionFactory.getCurrentSession();

    // create a query  ... sort by last name
    Query<Customer> theQuery = 
            currentSession.createQuery("Query goes here",
                                        Customer.class);

    // execute query and get result list
    List<Customer> customers = theQuery.getResultList();

        // return the results       
        return customers;
    }

我正在尝试执行此查询“SELECT DISTINCT Customer.* FROM Customer, Project WHERE Customer_Code=Project_Customer ORDER BY Customer_Name”

我尝试了以下方法：

"select distinct Customer from Customer as cus, Project as pro where cus.customer_code = pro.project_Customer order by cus.customer_Name"
“从客户中选择不同的 cus.customer_Code、cus.customer_Name as cus, Project as pro where cus.customer_code = pro.project_Customer order by cus.customer_Name"
“来自客户 cus, Project pro where cus.customer_Code = pro.project_Customer 按 cus.customer_Name 订购”

但是没有任何效果。我通常会收到错误Cannot create TypedQuery for query with multiple return using requested result type [com.timesheet_Webservice.entity.Customer]

这似乎意味着我没有像使用简单的“来自客户”查询那样获取客户实体的实例。如果是这种情况，我如何返回客户实体？如果不是，那我做错了什么？

【问题讨论】：

当您执行 Customer.* 时，查询应该选择 customer_Code 和 customer_Name 这两个 String 对象。但是您期望一个客户实体作为结果。
那么我如何将结果映射到客户实体？
试试select distinct cus from Customer as cus, Project as pro where cus.customer_code = pro.project_Customer order by cus.customer_Name
啊，太好了！请写一个答案，以便我接受它

标签： hibernate hql

【解决方案1】：

当您执行Customer.* 时，查询应该选择customer_Code 和customer_Name，它们是两个String 对象。但是您期望 Customer 实体作为结果。

进行查询以选择像这样的Customer 对象。

select distinct cus from Customer as cus, Project as pro where cus.customer_code = pro.project_Customer order by cus.customer_Name

【讨论】：