使用数组的JPA查找 [英] JPA lookups with arrays

问题描述

我有一个单向关系。在这里，我有Employee和Andress实体。在Employee实体中，我有以下代码：

  @OneToOne（cascade = CascadeType.ALL）
 @JoinColumn =HOME_ADDRESS）
私人地址homeAddress; 
  

我有一个Adress对象数组，并且想要编写一个将返回一个Customer对象数组的查找映射到这些地址。

  select e from Employee e where e.homeAddress.id IN'？'
  

我不知道如何处理'？'部分。是唯一选择循环地址数组，将id添加到一个字符串并将其作为参数传递给上面的查询，还是有办法将数组传递给查询并期望得到相同的结果？

解决方案

不，您不会将其作为字符串传递，而是作为ID的集合。而你的查询是无效的。它应该是：



 字符串jpql =select e from Employee e where e.homeAddress.id IN：addresses; 
 Set< Long> addressIds = Arrays.stream（地址）
 .map（Address :: getId）
 .collect（Collectors.toSet（））; 
 return em.createQuery（jpql，Employee.class）
 .setParameter（addresses，addressIds）
 .getResultList（）; 
  

这使用Java 8将地址数组转换为一组ID，但您当然可以使用goold old for循环。


I have an unidirectional relationship. Here i have Employee and Andress entities. In Employee entity i have the following code:

@OneToOne(cascade=CascadeType.ALL)
@JoinColumn(name = "HOME_ADDRESS")
private Address homeAddress;

I have an array of Adress objects and want to write a lookup that would return an array of Customer objects mapped to those adresses.

select e from Employee e where e.homeAddress.id IN '?'

I don't know what to do with the '?' part. Is the only option to loop over the address array, add id's to a string and pass it as a parameter to the query above, or is there a way to pass the array to the query and expect the same result?

解决方案

No, you don't pass that as a String, but as a collection of IDs. And your query is invalid. It should be:

String jpql = "select e from Employee e where e.homeAddress.id IN :addresses";
Set<Long> addressIds = Arrays.stream(addresses)
                             .map(Address::getId)
                             .collect(Collectors.toSet());
return em.createQuery(jpql, Employee.class)
         .setParameter("addresses", addressIds)
         .getResultList();

This uses Java 8 to transform the array of addresses into a set of IDs, but you can of course use a goold old for loop.

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