使用HQL选择集合 [英] Select collections with HQL

问题描述

我有以下类：

Person.java

  class Person {
 String name; 
设置< Hotel> visitedHotels; 
 String someOtherData; 
 
 public Person（）{} 
 $ b $ public Person（String name，Set< Hotel> visitsHotels）{
 this.name; 
 this.visitedHotels = this.visitedHotels; 
} 
 
 // getters& setters 
} 
  

Hotel.java

  class Hotel {
 //一些代码
} 
  

为了安全起见，someOtherData有时候不应该被加载。

所以我尝试了下面的HQL：

p>

 从Person p 
中选择新的Person（p.name，elements（p.visitedHotels）） 

或

 选择新人（p。名称，酒店）from Person p left join p.visitedHotels hotels 
  

但它不起作用 - 错误：无法在类Person上找到合适的构造函数。

是否可以选择酒店集合以及人名？

<使用集合映射查看Blaze-Persistence实体视图。解决方案

这可能只是你正在寻找的东西： https://persistence.blazebit.com/documentation/entity-view/manual/en_US/index.html#collection-mappings

允许拥有单独的DTO就像

  @EntityView（Person.class）
 interfae PersonView {
 String getName（）; 
设置< Hotel> getVisitedHotels（）; 
} 
 
查询中的用法，如
 
 CriteriaBuilder< PersonView> cb = entityViewManager.apply（
 EntityViewSetting.create（PersonView.class），
 criteriaBuilderFactory.create（Person.class）
）; 
 
列表< PersonView> list = cb.getResultList（）; 
  

创建一个查询，如

  SELECT person.name，visitedHotels_1 FROM Person person LEFT JOIN person.visitedHotels visitedHotels_1 
  

因为你似乎正在使用它来进行可视化，所以我建议将Hotel也映射为实体视图。

I have the following classes:

Person.java

class Person {
    String name;
    Set<Hotel> visitedHotels;
    String someOtherData;

    public Person() {}

    public Person(String name, Set<Hotel> visitedHotels) {
        this.name;
        this.visitedHotels = this.visitedHotels;
    }

    // getters & setters
}

Hotel.java

class Hotel {
    // some code 
}

For security reasons "someOtherData" should sometimes not be loaded.

So I tried the following HQL:

select new Person( p.name , elements(p.visitedHotels) ) from Person p

or

select new Person( p.name , hotels ) from Person p left join p.visitedHotels hotels

But it doesn’t work - error: Unable to locate appropriate constructor on class Person.

Is there a possibility to select the collection of hotels together with the person name?

解决方案

Take a look at Blaze-Persistence Entity Views with collection mappings. This might just be what you are looking for: https://persistence.blazebit.com/documentation/entity-view/manual/en_US/index.html#collection-mappings

Allows to have a separate DTO like

@EntityView(Person.class)
interfae PersonView {
    String getName();
    Set<Hotel> getVisitedHotels();
}

Usage in the query like

CriteriaBuilder<PersonView> cb = entityViewManager.apply(
    EntityViewSetting.create(PersonView.class),
    criteriaBuilderFactory.create(Person.class)
);

List<PersonView> list = cb.getResultList();

Creates a query like

SELECT person.name, visitedHotels_1 FROM Person person LEFT JOIN person.visitedHotels visitedHotels_1

Since you seem to be using this for visualization, I recommend mapping Hotel as entity view too.

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