如何使用Hibernate Criteria选择嵌套属性 [英] How to select nested property using Hibernate Criteria

问题描述

我有三个实体，例如注册，用户和国家。基本上，注册属于用户，用户属于一个国家。现在我正试着从注册中选择国家名称，如下所示：

  Criteria criteria = getSession（）。createCriteria（Registration.class） ; 
 ProjectionList projectionList = Projections.projectionList（）; 
 criteria.createAlias（user.country，usercountry）; 
 projectionList.add（Projections.property（usercountry.name），usercountry.name）; 
 criteria.setProjection（projectionList）; 
 criteria.list（）; 
  

失败并给我：

错误：org.hibernate.engine.jdbc.spi.SqlExceptionHelper  - '字段列表'中的未知列'usercountr1_.name'
 org.hibernate.exception.SQLGrammarException：未知列' 
  

生成的Hibernate查询：

  Hibernate：从voucherList中选择usercountr1_.name作为y0_ this_ 
  

我注意到在sql中没有加入。这就是查询失败的原因吗？如何解决这个问题？

解决方案

尝试类似于

<$ p $标准条件= getSession（）。createCriteria（Registration.class）;
ProjectionList projectionList = Projections.projectionList（）;

criteria.createAlias（user，u）; //这里我改变了
criteria.createAlias（u.country，usercountry）; //这里我改变了

projectionList.add（Projections.property（usercountry.name），usercountry.name）;
criteria.setProjection（projectionList）;
criteria.list（）;

I have three entities such as Registration, User and Country. Basically a registration belongs to a user and a user belongs to a country. Now I am trying to select country name from registration with the following

        Criteria criteria = getSession().createCriteria(Registration.class);
        ProjectionList projectionList = Projections.projectionList();
        criteria.createAlias("user.country", "usercountry");
        projectionList.add(Projections.property("usercountry.name"),"usercountry.name");
        criteria.setProjection(projectionList);
        criteria.list();

This fails and give me :

ERROR: org.hibernate.engine.jdbc.spi.SqlExceptionHelper - Unknown column 'usercountr1_.name' in 'field list'
org.hibernate.exception.SQLGrammarException: Unknown column 'usercountr1_.name' in 'field list'

Generated Hibernate query :

Hibernate: select usercountr1_.name as y0_ from voucherList this_

I noticed there's no join in the sql. Is this why the query failed ? How can I fix this ?

解决方案

try something like

Criteria criteria = getSession().createCriteria(Registration.class);
ProjectionList projectionList = Projections.projectionList();

criteria.createAlias("user", "u");  // here i changed 
criteria.createAlias("u.country", "usercountry");  //  here i have changed 

projectionList.add(Projections.property("usercountry.name"),"usercountry.name");
criteria.setProjection(projectionList);
criteria.list();

这篇关于如何使用Hibernate Criteria选择嵌套属性的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！