JPA / Hibernate + HQL / JPQL：使用BigDecimal参数选择DTO [英] JPA/Hibernate + HQL/JPQL: select DTO with BigDecimal parameter

问题描述

我们使用JPA和hibernate作为实现。假设我有以下DTO：

  public class SupplierInfoDto {
 private String supplierName; 
私人BigDecimal remainingFinances; 
 
 public SupplierInfoDto（String supplierName，BigDecimal remainingFinances）{
 this.supplierName = supplierName; 
 this.remainingFinances = remainingFinances; 
} 
 
 // getters / setters 
} 
  

<我似乎无法得到休眠正确找到这个构造函数。我首先尝试了以下查询（模型比这更复杂，我最终需要获取一些聚合（不直接在实体上），这就是为什么我要获取DTO而不是实体）：

 选择新的com.company.dto.SupplierInfoDto（s.name，f.remaining）
 FROM供应商的INNER JOIN财务f 
 WHERE s.id =：SupplierId 
  

然而，我得到了一个 org .hibernate.hql.ast.QuerySyntaxException：无法找到类异常的相应构造函数。

我选择的剩余的列在MSSQL中存储为一个浮点数（我知道，我知道钱不应该作为浮点数存储，但这是一个现有的系统，我不能只是改变这种数据类型）。

作为一个测试，我尝试了下面的查询，但是与上面相同的异常：

  SELECT new com.company.dto.SupplierInfoDto（s.name，NEW java.math.BigDecimal （10））
 FROM供应商s 
其中s.id =：SupplierId 
  

所以我的问题是：我如何让hibernate / JPA为上述两个查询找到合适的构造函数？

$ b

更新： remaining 属性在财务实体中是double类型的（不是我的决定）。

解决方案

我不确定为什么BigDecimal ctor没有被识别，但是你可以重载你的构造函数

如果你有

 公共SupplierInf oDto（String s，Double d）{
 this（s，new BigDecimal（String.valueOf（d）））; 
} 
 
 public SupplierInfoDto（String s，BigDecimal bd）{
 // set fields 
} 
  

不是，如果使用BigDecimal双构造函数，则数字基于double，所以仍然可能有舍入错误。通常最好使用BigDecimal字符串contstrctor

例如

 新的BigDecimal（0.1）
  

比
$ b更精确$ b

  new BigDecimal（0.1d）
  

< a href =http://rayfd.me/2007/04/26/the-evil-bigdecimal-constructor/ =nofollow>这篇文章解释了这个问题

We are using JPA with hibernate as the implementation. Suppose I have the following DTO:

public class SupplierInfoDto{
   private String supplierName;
   private BigDecimal remainingFinances;

   public SupplierInfoDto(String supplierName, BigDecimal remainingFinances){
       this.supplierName = supplierName;
       this.remainingFinances = remainingFinances;
   }

   // getters / setters
}

I cannot seem to get hibernate to properly find this constructor. I first tried the following query (the model is more complicated than this, and I need to fetch some aggregations eventually (not directly on the entities), that's why I'm fetching a DTO instead of the entities):

SELECT NEW com.company.dto.SupplierInfoDto(s.name, f.remaining)
FROM Supplier s INNER JOIN Finances f
WHERE s.id = :SupplierId

However, I get a org.hibernate.hql.ast.QuerySyntaxException: Unable to locate appropriate constructor on class exception.

The remaining column I'm selecting from is stored as a float in MSSQL (I know, I know money should never be stored as floats, but this is an existing system where I cannot just change this datatype)..

As a test, I tried the following query, but with the same exception as above:

SELECT NEW com.company.dto.SupplierInfoDto(s.name, NEW java.math.BigDecimal(10))
FROM Supplier s
WHERE s.id = :SupplierId

So my question is: How do I make hibernate/JPA find the appropriate constructor for the two queries above?

UPDATE: The remaining property is of type double on the Finances entity (not my decision).

解决方案

I am not sure why the BigDecimal ctor is not being recognised but you could overload your constructors

If you had

public SupplierInfoDto(String s, Double d) {
   this(s, new BigDecimal(String.valueOf(d)));
}

public SupplierInfoDto(String s, BigDecimal bd) {
   //set fields
}

Not that if you use the BigDecimal double constructor the number is based on a double so can still have rounding errors. It is usually best to use BigDecimal string contstrctor

For example

new BigDecimal("0.1")

is more precise than

new BigDecimal(0.1d)

This article explains this

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