如何将基元的ArrayList映射到单个列？ [英] How to map an ArrayList of primitives to a single column?

问题描述

假设我有以下情况：

Object Car有一个价格的ArrayList，它们都是数字。 Hibernate有可能将所有价格保存在一个列中吗？我知道这违反了第一种正常形式，但可能会出现这样的情况，您不希望它们被保存在单独的表格中，就像它在一对多或多对多关系中经典地完成一样。

在JDO中，我会通过将ArrayList保存在BLOB列中来轻松完成此操作。

一些有用的相关SOF问题：原始类型的ArrayList和使用Hibernate映射ArrayList 。

任何想法都将得到高度赞赏！

解决方案

我知道这是一个老问题，但对于任何想在JPA上下文中执行此操作的人来说，您都可以这样做

  import org.apache.commons.lang3.StringUtils; 
 import javax.persistence.AttributeConverter; 
 import javax.persistence.Converter; 
 import java.util.ArrayList; 
 import java.util.Arrays; 
 import java.util.List; 
 import java.util.stream.Collectors; 
 import java.util.stream.Stream; 
 
 @Converter 
 public class IntArrayToStringConverter implements AttributeConverter< List< Integer> String> {
 @Override 
 public String convertToDatabaseColumn（List< Integer> attribute）{
返回属性== null？ null：StringUtils.join（attribute，，）; 
} 
 
 @Override 
 public List< Integer> convertToEntityAttribute（String dbData）{
 if（StringUtils.isBlank（dbData））
 return new ArrayList<>（）; 
 
 try（Stream< String> stream = Arrays.stream（dbData.split（，）））{
 return stream.map（Integer :: parseInt）.collect（Collectors。 toList（））; 
} 
} 
} 
  

然后使用它这在你的实体

  @Entity 
公共类SomeEntity 
 {
 
 @I $ 
 @GeneratedValue（strategy = GenerationType.IDENTITY）
 private Integer id; 
 
 @Column 
 @Convert（converter = IntArrayToStringConverter.class）
 private List< Integer>整数; 
 
 ... 
} 
  

Enjoy !!!

Let's say I have the following situation:

Object Car has an ArrayList of prices, which are all numbers. Is it possible in Hibernate to save all the prices in a single column? I know this violates the first normal form but there might be cases when you don't want them to be saved in a separate table like it's classically done in One-To-Many or Many-To-Many relationships.

In JDO I'd do this easily by saving the ArrayList in a BLOB column.

Some useful related SOF questions: ArrayList of primitive types in Hibernate and Map ArrayList with Hibernate .

Any idea will be highly appreciated!

解决方案

I know this is an old question but for anyone trying to do this in a JPA context you can do this

import org.apache.commons.lang3.StringUtils;
import javax.persistence.AttributeConverter;
import javax.persistence.Converter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

@Converter
public class IntArrayToStringConverter implements AttributeConverter<List<Integer>,String>{
    @Override
    public String convertToDatabaseColumn(List<Integer> attribute) {
        return attribute == null ? null : StringUtils.join(attribute,",");
    }

    @Override
    public List<Integer> convertToEntityAttribute(String dbData) {
        if (StringUtils.isBlank(dbData))
            return new ArrayList<>();

        try (Stream<String> stream = Arrays.stream(dbData.split(","))) {
            return stream.map(Integer::parseInt).collect(Collectors.toList());
        }
    }
}

Then to use it something like this in your entity

@Entity
public class SomeEntity
{

   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Integer id;

   @Column
   @Convert(converter = IntArrayToStringConverter.class)
   private List<Integer> integers;

   ...
}

Enjoy !!!

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