如何从自定义Hibernate查询填充POJO类？ [英] How to populate POJO class from custom Hibernate query?

问题描述

我是Hibernate的新手，并试图在Spring MVC应用程序中使用它。我有如下的自定义查询：

findEmployees（）{
String queryString =选择E.firstname，E.lastname，A.city，A.state $ b $ from Employee E，Address A，where ....; //任何where子句
SQLQuery查询= this.sessionFactory.getCurrentSession（）。createSQLQuery（queryString）;
query.setString（...）//设置查询参数
return query.list（）;
}

这不起作用。查询运行，但它返回一个对象列表。
如何让Hibernate使用我的 MyResults 类？

  class MyResults {
 private String firstName; 
 //搜索中的其他字段
 
 @Column（name =FirstName）
 String getFirstName（）{
 return firstName; 
} 
 void setFirstName（String firstName）{
 this firstName = firstName; 
} 
 
 //其他getters& setters 
} 
  

我也不确定注释 MyResults



我试过几件事： return（List< MyResults>）query.list（）;


虽然这种转换不行。

我尝试过使用ResultTransformer：

  query.setResultTransformer（新的AliasToBeanResultTransformer（MyResults.class））; //在返回之前完成
  

但导致

ClassClastException：MyResults不能转换为java.util.Map。

有人可以显示我如何在Hibernate中正确设置这种查询？

解决方案 原因 ClassClastException：MyResults无法转换为java.util.Map 是Hibernate将列名的别名转换为大写 - firstName 变为 FIRSTNAME 。而且它确实需要 DTO 中的setter setFIRSTNAME（）。不知道，这是一个错误或功能。

要解决这个问题，请参阅我的回答你的其他问题：

将Hibernate查询结果映射到自定义类？

I'm new to Hibernate, and trying to use it in a Spring MVC application. I have a custom query like the following:

public List<MyResults> findEmployees() {
   String queryString = "select E.firstname, E.lastname, A.city, A.state
      from Employee E, Address A, where ...."; // whatever where clause
   SQLQuery query = this.sessionFactory.getCurrentSession().createSQLQuery(queryString);
   query.setString(...) // set query parameters
   return query.list();
}

This doesn't work. The query runs, but it returns a list of objects. How do I tell Hibernate to use my MyResults class?

class MyResults {
    private String firstName;
    // other fields in the search

    @Column(name = "FirstName")
    String getFirstName() {
        return firstName;
    }
    void setFirstName(String firstName) {
        this firstName = firstName;
    }

    // other getters & setters
}

I'm also not sure what annotations MyResults needs?

I've tried a couple things:

return (List<MyResults>)query.list();

though this cast doesn't do it.

I've tried using a ResultTransformer:

 query.setResultTransformer(new AliasToBeanResultTransformer(MyResults.class));  //done before the return

but that causes an

ClassClastException: MyResults cannot be cast to java.util.Map.

Can someone show me how to set this kind of query up correctly in Hibernate?

解决方案

The cause of ClassClastException: MyResults cannot be cast to java.util.Map is that Hibernate converts aliases for column names to upper case — firstName becomes FIRSTNAME. And it is really need the setter setFIRSTNAME() in the DTO. Don't know, it is a bug or feature.

To solve this issue, please, see my answer to your other question:

mapping Hibernate query results to custom class?

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